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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1482
Registered: 6-2009
Posted on Friday, 10 July, 2015 - 10:53 am:   Edit PostDelete PostView Post/Check IP

I have done a quick search an looking through of the threads returned when I search on "temperature range" but still have no real answer.

We all know that the Crewe UE36600 thermostat begins to open at 88C/190F, or there about. These things aren't precision instruments and the tolerance is +/-5% of rated temperature.

The question is, what is the upper limit of "Within Normal Limits" (WNL - in medical speak) for the operating temperature on the Shadow series cars? I have yet to find a definitive reference to this temperature, and it would be very handy to know. Even the latest, "I think I'm running hot," threads never get around to defining what "running hot" actually is.

I cannot believe that the lower and upper limits on operating temperature are just a few degrees apart. I'd expect the range to be fairly wide, but there has to be an, "if you're above this temperature you definitely have cooling/overheating problem."

It's been said, repeatedly, that if you ever hear the overheat warning buzzer it's likely "already too late" [which makes it a very crappy warning mechanism if the damage to the engine is already done].

If anyone knows, either from years of observed experience or from one of the manuals, what the upper range of WNL is, please post it.

Brian
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Christian S. Hansen
Experienced User
Username: enquiring_mind

Post Number: 21
Registered: 4-2015
Posted on Friday, 10 July, 2015 - 02:55 pm:   Edit PostDelete PostView Post/Check IP

Brian...
I wil take a stab at your question and posit my own variant, which is, where do those "normal" limits, both at the high and the low end, appear on the gauge, and then supplement that with the question of what is "acceptable" even if not "normal"? I am always very uneasy with gauges that do not have numbers. The temp gauge on my Early MPW Shadow (CRX2508) has a very wide white band that fills the majority of the gauge. It is easy/convenient to assume that anything within that band is normal, but I also feel this is overly simplistic. To me "normal" means "not varying" significantly from a constant position. I would expect a properly temperature moderated engine to maintain operating temperature within a very narrow band, perhaps +/- 5 degrees much like a houshold temperature thermostat where if you set the desired temperature to say 72F, you expect it to maintain that temperature by turning the heat on or off whenever the sensed temperature varies by only a few degrees. I would expect the same from the thermostat in the engine and that if circumstances are such that it cannot maintain a constant temperature, where that constant temperature would be indicated on the gauge as the needle not moving appreciably in one or the other direction, and the needle began moving toward the right (hotter) I would immediataely start worrying that something was amiss. Therefore it is my suspicion that the overly wide white band is misleading and that by the time the needle gets to the top end of that band, that indicates two things to me. First, the constant operating temperature is no longer being maintained, and secondly the engine is getting hotter which brings us back to your question which is not so much what is the upper and lower "normal" range, but rather what is an acceptable variation as opposed to what is indicating some problem with the system. In a thread earlier this year I noted my concern of problems since my operating temperature (as indicated with a heat gun to be 210F) was observed as being just a needle width above the top end of the white band in the gauge. This gauge position I deemed to be worringly "not normal", rather than being interpreted as "just a bit above normal" and was thus the cause for considerable alarm and precipitated the conclusion that there was a heating problem with the system. What I am saying is that I do not and never would consider anything within the white band to be normal. To me, "normal" is indicated by the two small dots that are just about at the midpoint of the white band. Anything that strays from that area more than momentarily is cause for alarm. Anything above is getting hotter than normal, and on the other side, not operating hot enough. To me 200F is NOT normal even though it may be at the top end of the white band. Maybe I have unrealistic expectations. If the thermostat opens at 185-190F then THAT is the "normal range" which a properly operating system should be able to maintain. If the entire white band on the gauge is intended to indicate "normal" then 180F would be the far left end, and 190F would be the far right end. On the other hand, is 200F, or even 210F "acceptable", even if perhaps not "normal"? What is the opinion of others in this regard?
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1483
Registered: 6-2009
Posted on Friday, 10 July, 2015 - 11:43 pm:   Edit PostDelete PostView Post/Check IP

Christian,

I went back and read Thermostat Issues and Selection again and found that Don Elliott had documented something in TSD4700, the Workshop Manual for the 20K SZ cars. It indicates that the thermostat should reach "fully open" [which means that the bypass port is only then fully closed] at a temperature ranging from 210-215F/98.8-101.7C. To me, this sets the approximate upper limit, which I suspect in reality is a few degrees higher since I doubt the ability of a cars cooling system to maintain the exact temperature at which the bypass closes in really hot weather, under heavy load, etc. So, for myself, another 5 degrees F would not make me freak out if this is where things held rock steady under demanding conditions. Since the UE36600 thermostat was the one originally used on all these cars the information regarding thermostat behavior should apply to any that use it.

So, it would seem that the upper end of WNL could vary between 210 and 220 F depending on a number of factors beyond individual control (including the initial opening temperature and temperature of maximum excursion of the thermostat).

My understanding has always been that on the SY2 series or any of the cars that had the 4-way gauge or temperature gauge that has "the white band" that anywhere within that band is WNL. There is a reason, both in medicine and with regard to engine operating temperature, the concept of a normal lower and upper limit exists. There are a multitude of factors that can combine to make the given placement within these limits occur on any given day at any given moment. There are very few times when "ideal" is going to be held as a rock steady norm. In the case of our cars, the temperature gauges, though not marked with numbers, do function as a true temperature gauge, which means they will show significant variation as temperature varies. On mine, in cold weather, the needle usually rests around 1/3 of the way up the white band and pretty much stays there. During warmer weather it's usually above 1/3 but slightly below 1/2 way up the band when the car is just coasting along the highway. This is pretty much standard in "coast mode" even in hot weather, but the needle can and will go up to very near the upper end of the band if the AC is on and I am stuck in stop-and-go traffic under high heat conditions. Most of us who drive modern cars are really not accustomed to having temperature gauges that act as temperature gauges. The gauge (and one really shouldn't call it that) that was in my 1999 Jag was designed to sit at dead center so long as the car was operating anywhere within its acceptable temperature range. My 1989 Cadillac has no temperature gauge at all (idiot light).

A 20-25 degree F normal operating temperature range seems quite reasonable to me. I expect that the ability of a radiator system to dispose of heat to be much better when temperatures are moderate than when it's really hot outside. From the way you describe things you appear to consider "normal" and "ideal" to be the same thing while I consider "normal" to be within whatever range is acceptable and does not cause damage to the engine from running either too cold or truly overheating.

Brian, who would still love more input
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1487
Registered: 6-2009
Posted on Saturday, 11 July, 2015 - 03:53 am:   Edit PostDelete PostView Post/Check IP

Christian,

I also e-mailed Don Elliott, the first named author on the thermostat article, to find out where precisely he got the mentioned temperatures for the melt-out point for the lead plugs as well as operating temperatures. Here is the pertinent part of his reply to me:

Sure, the 124 C temp was cited in TSD 4700 page L5-1 middle of the left hand column. The Crewe UE thermostat begins to open at 88 C and according to this same page is fully open at 102 C. The normal operating temperature is given as 99 to 102 C.

Since all of the temperature regulation is controlled by the thermostat, at least if all is functioning as designed, the same data should apply to the SY cars as well.

This means that the normal "settled down" operating range is approximately 210-216F. There is, of course, the potential for a bit of "slop" at the top of a few degrees if the individual thermostat in question doesn't reach full closure at the noted temperature. They aren't precision instruments and while they are individually consistent in their behavior, different examples can vary +/-5% and still be considered OK. I doubt that there is any testing on these things at the point of production, so if you want to know what your current or intended replacement thermostat's temperature response actually is you'll have to test it out yourself on the stove top.

Given that the plug melt-out point is very well above the normal operating temperature range, I fully expect that there can be some "spikes" that are above that range under demanding conditions in hot weather but that should never even come close to getting near the melt-out point, which is a full 40 degrees F above the top of the ideal normal operating range.

Brian
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Christian S. Hansen
Experienced User
Username: enquiring_mind

Post Number: 22
Registered: 4-2015
Posted on Saturday, 11 July, 2015 - 06:30 am:   Edit PostDelete PostView Post/Check IP

Brian...
This subject is very unsettling for me, but I do believe that you have identified that the problem is a matter of semantics and how one defines "normal". Yes, I consider "normal" and "ideal" to be the same, the desired state of things, and as indicated on the gauge as being in the middle where the two white dots are located. "Acceptable" on the other hand is when things begin to get out of hand, and we are talking about the excessive heating end of things here, rather than being too cold. To me, acceptable then transitioning to unacceptable is when the operating conditions (ambient temperatures, engine load, or system problems) begin to exceed the ability of the designed system to compensate and keep temperatures at that normal/ideal range. Based on this vision, the range for normal/ideal is narrow, whereas the acceptable range is a lot wider, extending all the way up to the next range which can be characterized as "excessive/unacceptable" and beyond that the next range being "imminent disaster". Where the transition points are is what gives me stress, but I would venture to say, but without any specific expert basis for that feeling, that "normal" is within 5 degrees or so of the opening temperature rating of the thermostat, acceptable extends up to 200F or so, excessive extends up to 220F or so, and imminent disaster rears it ugly head above that, and certainly by 250F. Call me paranoid, but I do not feel comfortable with my engine running at 220F (heat gun reading) and hovering just above the white band at at the end of the gauge with little room for anywhere else to go other than to the pin, given that to me "normal" also means "room to spare". Under these circumstances I find it difficult to simply relax and tell myself that this is "normal" especially given that these conditions are noted with ambient temperatures in the 70F range. Due to the cooling effect of the immediate proximity of the Pacific Ocean witnessed here in the San Francisco Bay Area, the micro-climates are various and clearly delineated. It can be foggy and 60F at the beach, sunny and 75F across the bay where I live, but 100F only a few more miles inland on the same day. Given my apparent heat readings and gauge indications, I dare not ever even consider driving out to those 100F areas as I am quite sure that the load from the additional ambient temerature would overwhelm what I worry is an already overtaxed and improperly operating system. Such should not be. All the other cars operate under those same conditions presumably with their temperature gauges indicating normal, rather than hanging just under the critical range on the gauge. To summarize, I would simply say that if those temperatures are normal, then I am surprised that they are not indicated as such on the gauge.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1489
Registered: 6-2009
Posted on Saturday, 11 July, 2015 - 06:50 am:   Edit PostDelete PostView Post/Check IP

Christian,

I can do no more than quote chapter and verse, which I have. If the statement from Crewe that normal is what was quoted will not satisfy you, and you insist that what they define is normal extends beyond that, there is no hope of coming to any mutual shared position of any sort.

It's clear that if Crewe defines up to 216 F as solidly normal operating temperature, and they're the ones who manufactured the cars, it doesn't get any more definitive than that. That's about as "black and white" as one could hope for. Four degrees above that, if it remains the set point, and that's easy to test out, falls into the "within statistical variation" limits in my book.

When it comes down to it your temperature gauge reading is irrelevant if your IR readings are "good," you trust your IR thermometer, and they remain consistent over test drives in a range of heat conditions. You could easily have a bad temperature sender or gauge and then that becomes an issue to resolve.

For myself, I refuse to stress out over variations that are within a range identified by the manufacturer as "normal" +/- a slop factor for non-precision engineering, and automotive cooling systems are not precise by any meaningful definition of that term.

Brian
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1492
Registered: 6-2009
Posted on Saturday, 11 July, 2015 - 07:37 am:   Edit PostDelete PostView Post/Check IP

P.S.: It's easy enough to compare how your other car(s) [preferably with V8 engines] behave as far as the general contours of operating temperatures.

I would be shocked if any automobile's top "normal" temperature would be within a few degrees of thermostat opening temperature, particularly in a bypass system. Thermostats open well before the time where thorough heat soak has occurred. The system temperature at time of opening would generally not be held within +/- a few degrees F because they begin opening when they do and in bypass systems there is a period of time, and sometimes in certain conditions this becomes a stasis point, where coolant is being permitted to circulate partially to the radiator and partially through the bypass port. You're likely to see continued heating until the operating temperature reaches whatever is required for the bypass port to be closed by the thermostat. After that a upper limit stasis point should be arrived at fairly rapidly.

It might give you some comfort to see how your other cars, about which you don't have any concerns, actually behave.

Brian
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Christian S. Hansen
Experienced User
Username: enquiring_mind

Post Number: 23
Registered: 4-2015
Posted on Saturday, 11 July, 2015 - 08:07 am:   Edit PostDelete PostView Post/Check IP

Brian...
I submit that we are talking past each other, perhaps like the fable of the three blind men and the elephant where each interprets reality under their own set of circumstances.
The issue is one of "normal" vs "acceptable". If "acceptable" is circa 215F, my concern is that my set of circumstances reaches that range under what would otherwise be considered "normal" or "at room temperature and in the absence of any other load factors".

My concern is that if my engine seems to run at the upper limits of the acceptable operating range (that is, presumably with thermostat fully open and bypass fully closed, and with the system accordingly having done everything in its ability to increase coolant flow thru the radiator and thus reduce coolant temperature) even under my "normal" operating conditions, that is ambient room temperature, level terrain, no A/C, no passengers other than driver, etc, there is no margin left which only baits the concern of what would happen if any load factors or ambient temperature were to be added to the equation. Basically my concern is that it is neither normal, expected, nor cause for complacency when the top end of acceptable temperatures are generated by otherwise no load operating conditions. I recognize that this is a variant to your original question which was, if I may paraphrase, what is the upper limits to acceptable operating temperatures, since "normal" is ambiguous.

It is hoped that some other members will submit their observations as to their operating conditions (ambient temp, A/C yes or no, passenger loads, level or pulling hills, electric fans, etc) and where the needle is indicated on their gauge under "their" normal operating conditions.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1493
Registered: 6-2009
Posted on Saturday, 11 July, 2015 - 08:23 am:   Edit PostDelete PostView Post/Check IP

Christian,

That data from others would be welcome. However, it also may never be forthcoming.

You could still do quite a few easy tests to see if your own car remains WNL when additional demands are added. There was enough small variation over the decades that I'd expect some variance among vehicles, even with exactly the same equipment and under exactly the same conditions, due to idiosyncratic factors.

I see no reason to torture yourself over this when you already have the equipment and intelligence to do the simple checking necessary to see if your concerns about escalation of heating take place without ever putting your engine into the "point of no return" range. When you get the chance to get back to this car it makes a lot more sense to check this out rather than searching for an ideal that may not actually apply for your particular example. Take the time to put your mind at ease through data collection. If you're never getting above 220 F under high demand then you're A-OK. It's worth the effort.

All indications are that your temperature gauge is wonky in some way. It would make no sense for true ideal temperature to be at the top of a "normal operating band" gauge. I'd say your initial intuitive sense regarding the "two dots" (which neither of my cars has) would be the logical area around which the needle should rest when typical operating temperature is achieved. Most designers aren't trying to make these things confusing and marks like you describe typically indicate something, well, typical.

Brian
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 822
Registered: 5-2012
Posted on Saturday, 11 July, 2015 - 08:36 am:   Edit PostDelete PostView Post/Check IP

Brian/Christian

No data from me I'm afraid - my SY1 does not have a temperature gauge. I cannot imagine why the Crewe engineers failed to fit such an essential gauge. Something I intend to remedy soon.

I will take some IR readings this weekend.

Geoff
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1495
Registered: 6-2009
Posted on Saturday, 11 July, 2015 - 08:57 am:   Edit PostDelete PostView Post/Check IP

Geoff,

There are a great many cars that were never fitted with temperature gauges. Some had them deleted, or changed over to the steady state equivalent of an idiot light, because so many became completely unnerved by the fact that real temperature gauges, particularly those most sensitive to whatever their "normal range" should be, swing widely. That's even been discussed on these forums in the past, at least if memory serves.

While I regularly monitor all gauges in my cars that have them, I also value so-called idiot lights even more. I have always been far more acutely aware of sudden state changes, and particularly visual cues, than I am of slow creeping changes like a needle edging its way up a gauge. This is even more true if I am distracted.

My experience in now over 35 years of driving is that cars built post 1960 very, very seldom overheat. I only had one car that did, a 1996 Chrysler Sebring, and it did so because it somehow managed to create thermostat failure of "sudden snap shut" type about once every two years. After the second occurrence of this I started changing its thermostat every two years as preventive maintenance. I have never done this in any other car, now including my Rolls-Royces, since I've never experienced a single other thermostat failure. They generally seem to have a functionally perpetual service life.

One of the reasons I so hate the overheat buzzer in our cars is because, from all historical descriptions, it's not a warning but a notification that you're scr*w*d.

I'll be curious to see your readings.

Brian
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David Gore
Moderator
Username: david_gore

Post Number: 1682
Registered: 4-2003
Posted on Saturday, 11 July, 2015 - 09:30 am:   Edit PostDelete PostView Post/Check IP

I have been following this discussion with much interest but have no information in my archives that is relevant to the original request. However, I have the following general comments:

1. The Shadow and derivatives cooling system is more than adequate for hot climates such as Australia. The gauge indication for DRH14434 would increase slightly if the air conditioning was working at full capacity due to heating of the air passing across the condenser before entering the radiator core.

2. The temperature gauge is only an indicator of coolant temperature and not an accurate temperature measuring device - as such the position of the needle will vary between various cars depending on the inbuilt tolerances in the sensor and gauge.

3. The engine coolant temperature can safely be above 100deg Celsius [212deg Fahrenheit] before boiling occurs due to the system pressure being above atmospheric due to the steam valve/radiator cap pressurising the system. For every 1 psi of pressure increase above atmospheric, the boiling point of the coolant increases by approximately 1.4deg Celsius [2.5deg Fahrenheit], the exact increase of the water/ethylene glycol mix would require access to SVP [Saturation Vapour Pressure] tables for the mixture. I have not been able to find the pressure release value for the steam valve after a short search.

Suffice to say, there is a significant difference in coolant temperatures from a wide open thermostat condition to the temperature in a pressurised system at which the steam valve will open. I am in no doubt the Rolls-Royce engineers would have specified a steam valve opening pressure that would ensure a coolant temperature less than that which caused engine damage on the factory test bed.

The car temperature gauge could easily be calibrated to actual coolant temperature with an hour or so of measuring the header tank coolant temperature of the running engine with a suitable thermometer and noting the gauge reading after a series of reducing the air flow through the radiator by blocking off cooling air with a blanket to increase the engine temperature.
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Robert Noel Reddington
Prolific User
Username: bob_uk

Post Number: 274
Registered: 5-2015
Posted on Saturday, 11 July, 2015 - 10:34 am:   Edit PostDelete PostView Post/Check IP

I fitted a temp gauge to my car and checked it with an IR gauge. IR gauge 89c car gauge 90c.

Normal Driving.

The car runs at a constant 90c. UK.

If the heater water valve is opened the gauge will drop to 85c then the stat will move and the temp goes back to 90c. If the aircon is turned on then the gauge still shows 90c. The extra heat from the aircon is slow in developing so the stat keeps pace.

On the hilly bits the temp can go to 95c a but quickly backs down to 90c on the flat bits. If the temp goes above 95c I back off a bit.

30c in the UK is hot weather 35c and above are rare. So my cooling system has an easy time.
In the winter the temp is again a constant 90c.


I don't like guesstimate flow rates when testing radiators. The best way is to get a TV camera in the tanks and look for scale. I have seen rads with half the tubes blocked with scale. Rad flush etc are generally not very good. I always have a new core.

The old method of removing the stat to check leaves the bypass open. Not good. So using a wooden plug that is tall enough to nearly touch the thermostat elbow so it can't fall out. The cooling system can be checked sans stat. The wooden plug would be a handy get you home tool should the thermostat fail shut which they do.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 823
Registered: 5-2012
Posted on Saturday, 11 July, 2015 - 12:17 pm:   Edit PostDelete PostView Post/Check IP

I guess it's a matter of personal preference, but mine is very definitely for a gauge. I'm not too fussed what the gauge actually reads in normal operating conditions, but I am interested in the relative movement from the "norm". Also, keeping an eye on the time it takes for the engine to reach operating temperature is a good way of detecting thermostat/cooling problems.

Bob - I am going to fit a gauge in my SY1. Where did you position your gauge? Did you buy a gauge with a classic appearance, to try and blend in with the layout of the dashboard? I'd be grateful for any details of the gauge you used and how you installed it.

Geoff
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Christian S. Hansen
Experienced User
Username: enquiring_mind

Post Number: 24
Registered: 4-2015
Posted on Saturday, 11 July, 2015 - 06:46 pm:   Edit PostDelete PostView Post/Check IP

Out of curiosity I looked at the workshop manuals that came with my 1967 MPW Silver Shadow Coupe CRX2508 (early in the series). While they have no TSD number, they are original 1983 Rolls-Royce supplied reprints of their 1965 edition, which is completely devoid of any later serial number or SZ modifications which can serve to confuse. This edition is strictly applicable to the early engines and reports variations from what Don Elliott cited.

The only references I could find were at Volume I, Section A1, Specifications, Cooling System, where it is noted: "Coolant temperature is controlled by thermostat opening temperature." Apparently the earlier the serial number, the lower the opening temperature, or rather the later, the higher, as it is noted that prior to #2986 for Corniche, opening temperature was 79.5C to 83.5C (175F to 182F), and after that serial number, a bit higher at 85C to 89C (185F to 192F). Perhaps I misread when I infer from the words "coolant temperature is controlled by thermostat opening temperature" that the intended operating coolant temperature was to be maintained at the thermostat opening temperature, and that this would be accomplished by the thermostat opening due to sensed temperatures above this point prompting the thermostat to begin opening and thus allow a variable amount of coolant (determined by the necessary demand for cooling) to flow to the radiator where it could be cooled and returned to the engine in order to reduce the temperature back to the opening temperature at which point the thermostat would reverse and close sufficiently to bring the temperature back up to the opening point again, et cetera, thereby maintaining a constant ideal operating temperature at the thermostat opening temperature.

The other reference I could find was in Section L, Cooling System, Page L1, General Information, Introduction, "A thermostat valve...prevents circulation of the coolant through the radiator until the engine has reached normal operating temperature. It is also noted that later Shadows had the temp gauge deleted and an illuminating warning panel fitted, but that the Corniche always continued to have the gauge, which explains why some saloons do not have the gauge, but also repeats the inference that "normal operating temperature" was synonymous with thermostat opening temperature.

Final reference is in Section L3, Thermostat, Page L7, "Thermostat has its opening temperature stamped on the base of the unit, for example, 80C (190F)", which is curious since that temperature is similar to the opening temp for the early serial number range engines, and I would suspect is a hold over from the Cloud III engine. My conclusion is that the early engines were designed to run at lower temperatures than the later ones referenced by Don Elliott, so comparing early with late is a case of "apples and oranges".

Robert...In my dreams, my engine operates at your temperatures!!
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1496
Registered: 6-2009
Posted on Saturday, 11 July, 2015 - 11:44 pm:   Edit PostDelete PostView Post/Check IP

Christian,

This will be my last entry on this subject, and it's a quotation:

The thermostat is a simple proportional control valve. The hotter the temperature is, the wider it opens. It will modulate its opening to meet a fluctuating engine temperature and will try to hold the temperature steady using the characteristics of the wax pellet in the particular thermostat (sort of a set point, but not really) until it is wide open. Once it has reached its maximum opening and the bypass is shut, the thermostat control valve can no longer influence the coolant temperature. Crewe says the UE thermostat is wide open at ~102 C. Beyond that point temperature control then passes to secondary factors such as the ambient air temperature, the air flow rate through the fins on the grille and the radiator core, the functioning of the auxiliary fans, the shroud, the heat loading on the engine, and the cleanliness of the heat transfer surfaces throughout the car. If any of these factors are not favorable the car will overheat.

If the same freakin' thermostat is used, and it is, and in any system that's the primary temperature control, the system is limited by the factors mentioned above and the qualities of the thermostat.

I already mentioned that in some cars in certain environmental and operating conditions stasis will be reached when the thermostat is neither completely open nor completely closed. One would expect when this confluence of events occurs that the actual temperature would be on the cooler end of the operating range. 90 degrees C is running far too cold based on the fact that the thermostat is supposed to start opening at 88 degrees C. An engine perpetually running cold will experience far more wear than one running slightly hot, but not overheating.

Torture yourself to death over this as it's become clear that's what you actually want to do. Normal operating temperature in any automobile engine is a temperature range, not a set temperature.

I have already pointed out that the 80 degree C opening temperature is errata since I have yet to see any UE36600 thermostat not stamped with 88 degrees C as its rated opening temperature. That error was carried through documentation for years, but the devices don't lie. No manufacturer would continue to recommend that same thermostat for cars produced over a 25 year period if there were an actual 8 degree C difference in where the actual opening temperature was supposed to be. That would make no sense and cause no end of legal problems.

Brian
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 1498
Registered: 6-2009
Posted on Sunday, 12 July, 2015 - 12:59 am:   Edit PostDelete PostView Post/Check IP

P.S. Convert 190 F to C and see what you get.
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Christian S. Hansen
Experienced User
Username: enquiring_mind

Post Number: 25
Registered: 4-2015
Posted on Sunday, 12 July, 2015 - 06:08 am:   Edit PostDelete PostView Post/Check IP

I don't feel tortured. I was simply pointing out that the documentation for the earlier cars appear to have lower thermostatic opening values.

It is however bothersome to me that under "room temperature and lower" conditions, my engine as a single example runs with the thermostat wide open (in a state, as you have noted, which is without further excess capacity to affect coolant temperature) and with the gauge needle almost pinned just under hot. In that personal limited instance, I find it difficult to accept that these conditions should be dismissed as being "within normal limits" since even if that premise is accepted, they are at the upper end of those limits with nowhere else to go but "hot".

My "torture" is, I suppose, my inability to consign myself to operating in a low ambient temperature environment and no engine load where those conditions result in a maximum thermostat opening with no additional resources available to counteract additional heating influences, and to console myself that such should be considered normal.
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Randy Roberson
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Username: wascator

Post Number: 490
Registered: 5-2009
Posted on Sunday, 12 July, 2015 - 11:00 am:   Edit PostDelete PostView Post/Check IP

in general the Car's cooling system was designed for the heat load resulting from high-speed motoring; therefore if you are overheating at normal sane cruising speeds circa 50 to 70 mph, something is not in good condition. Radiators deteriorate in a few ways and it is gradual so unseen. Typical operating temp about 90C. and the upper end is limited by the boiling point of the coolant (water-glycol) mixture but the temp should not rise much no matter the adverse condition, if She's in good shape. It will vary some, though.
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Geoff Wootton
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Username: dounraey

Post Number: 827
Registered: 5-2012
Posted on Sunday, 12 July, 2015 - 01:36 pm:   Edit PostDelete PostView Post/Check IP

I took my car out for a short (15 mile) run today. Just standard no-load motoring. On returning home, I immediately took a reading from the top of the thermostat housing whilst the engine was still ticking over, with an IR gun. 190F (88C). This ties in quite closely with Robert and Randy's figures. I did wonder if this relatively low figure may be due to us all using the the stant thermostat, which opens at 176F (80C) rather than 190F (88C) for the OEM thermostat. But I'm figuring once the thermostat is open, then the running temperature is determined by the design of the cooling system. Certainly the OEM thermostat would allow running temperature to be reached more quickly, but I'm not so sure the slightly longer time the stant must take makes any real difference in practice.

I know it can be harmful to run modern cars at too low an engine temperature. These run at higher temperatures to allow a more complete burn of the fuel. If, for some reason they start running at a lower temperature, the ecu thinks the engine is still warming up and enrichens the mixture. This excess of gasoline washes the oil from the cylinder walls which leads to greater wear. On the Rolls, there is obviously no ecu to decide it wants to spray neat gasoline onto the bores. The carbs are tuned according to the normal running temperature of the engine, so excess gasoline cannot be introduced. I'm wondering if this is the reason it is ok to run these cars at the lower temperature. I would obviously appreciate more information on this.

Geoff
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Robert Noel Reddington
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Username: bob_uk

Post Number: 276
Registered: 5-2015
Posted on Monday, 13 July, 2015 - 06:06 am:   Edit PostDelete PostView Post/Check IP

The ecu only commands a rich mixture when the engine is cold, at about 50c an engine will run on the normal mixture. At 50c petrol goes to gas.

The bearings pistons and rings etc. Will run fine at lower temps.

The lowest temp IMO that is OK to run an engine at is 80c and highest is 105c.

My car like Geoff (88c) runs at 89c.
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John Kilkenny
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Username: john_kilkenny

Post Number: 206
Registered: 6-2005
Posted on Monday, 13 July, 2015 - 10:10 am:   Edit PostDelete PostView Post/Check IP

Because we mainly drive late model cars where the coolant needle always sits neatly in the middle of the gauge it's easy to get concerned when our pride and joy shows signs of possible overheating on very hot days, a long period of stop/start driving or an extended uphill stretch.
I've had my car (SRH1405) for thirty two years and even though advice in this forum suggests that its cooling system will easily cope with all conditions I used to worry when the gauge would occasionally go past the edge of the white band. This occurs even though at various times all of the cooling system components have been replaced or rebuilt. No sign of boiling of course, as David has pointed out the combination of 50% glycol and a pressurised system will extend the boiling point to 250 F or thereabouts.
I have long since stopped worrying about it though I am still relieved when the needle goes back into white space after such an event. Of course if it ever approached the HIGH mark I would investigate further.
For an excellent and thorough description of the automotive cooling system and how temperature control depends on a lot more than the thermostat see the following article by a MGA owner.

http://mgaguru.com/mgtech/cooling/cool_200a.htm

John
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Robert Noel Reddington
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Username: bob_uk

Post Number: 300
Registered: 5-2015
Posted on Thursday, 16 July, 2015 - 10:15 am:   Edit PostDelete PostView Post/Check IP

MGA Guru. Cooling thingy is correct and worth reading.

Missing was cavation. In a properly designed and maintained system cavation doesn't happen so is of no worry.

Main cause of cavation is restricted flow through the radiator due to scale. This is a double whammy because the rad has less capacity to cool and the cavation is allowing steam bubbles to form on the outside of the bores etc. Especially around the exhaust port area. The next cause is bad design of the water pump and flow to and from, and people modifying stuff in this area.

I have seen bottom hoses try to collapse when engine is revved. Sometimes due to wrong hose being bent to fit and other times the hose insides are falling apart.