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Bob Livermore
New User
Username: livermoreb

Post Number: 2
Registered: 5-2007
Posted on Thursday, 27 November, 2008 - 01:10:   Edit PostDelete PostView Post/Check IP

Does anyone know of an alternative for the Rolls Royce Thermostat for a Silver Cloud III?
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Martin Cutler
Frequent User
Username: martin_cutler

Post Number: 94
Registered: 7-2007
Posted on Thursday, 27 November, 2008 - 19:14:   Edit PostDelete PostView Post/Check IP

gidday Bob,

To fit a modern stat, first you have to block off the by-pass hose. Next you buy a stat that is bigger in diameter than the hole, (there isn't one in Oz that is a perfect fit). Next you machine down the outer part of the stat on the lathe to the correct size. Oh, and you need to get one that is as low as possible, around 77 degrees is good.

Cheers

Marty
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Bob Livermore
New User
Username: livermoreb

Post Number: 3
Registered: 5-2007
Posted on Thursday, 27 November, 2008 - 22:27:   Edit PostDelete PostView Post/Check IP

Thanks Marty

Looks like a lot of effort. Maybe I'll have to bite the bullet and get an RR one - problem is they cost almost UK£250 a piece!

Bob
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Martin Cutler
Frequent User
Username: martin_cutler

Post Number: 95
Registered: 7-2007
Posted on Friday, 28 November, 2008 - 20:13:   Edit PostDelete PostView Post/Check IP

Considering a modern stat costs around $10AUS, I would think that it was worth while! 250 pounds is getting on for $750, you could almost buy the lathe for that!

Marty
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Bob Livermore
New User
Username: livermoreb

Post Number: 4
Registered: 5-2007
Posted on Saturday, 29 November, 2008 - 03:47:   Edit PostDelete PostView Post/Check IP

True. Any idea what stat will fit - I believe a Jaguar XJ6 one is just a little bigger. Some stats have a rubber sealing ring - is this needed to prevent corrosion between the stat and the aluminium of the head?

Bob
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Martin Cutler
Frequent User
Username: martin_cutler

Post Number: 96
Registered: 7-2007
Posted on Monday, 01 December, 2008 - 21:01:   Edit PostDelete PostView Post/Check IP

Hi Bob,

You will need to cut a new paper gasket, as the one on there will probably tear when you pull it off. I don't think there is room for a rubber ring, just a smear of your favourite goo on either sides of the new gasket when you put it together. What temp does the XJ6 open? A lot of modern cars open well into the 90's, and run high pressure caps to stop from boiling.

Marty
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Bob Livermore
New User
Username: livermoreb

Post Number: 5
Registered: 5-2007
Posted on Wednesday, 24 December, 2008 - 01:05:   Edit PostDelete PostView Post/Check IP

Well, I found one that fits - it is a Quinton Hazell QTH208 which is the right diameter and temperature (80 C) so let's see how she goes. It cost £5.92 in the UK. They also do another - QTH 528 AT £23.66 - which has a slightly higher opening temperature at 82 C but looks deeper and so might be a better bet.

I have fitted my Skoda one and will let you know if it is successful. I am concerned that it might overheat in the summer, which is probably why it was taken out in the first place.
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1536
Registered: 4-2003
Posted on Wednesday, 24 December, 2008 - 09:09:   Edit PostDelete PostView Post/Check IP

Merry Christmas Sir Vladmir Skoda. We all hope that, for 1.99 Forint, your Rolls-Royce gives you more pleasure than a Trabant. That thermostat saved you all the dosh of a tank of gas. Nice legs. Shame about the squiggy stockings.
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Bob Livermore
New User
Username: livermoreb

Post Number: 6
Registered: 5-2007
Posted on Monday, 29 December, 2008 - 03:16:   Edit PostDelete PostView Post/Check IP

I'll have some of what you're drinking please!!
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1540
Registered: 4-2003
Posted on Monday, 29 December, 2008 - 04:11:   Edit PostDelete PostView Post/Check IP

Simple. Nothing.

Just why skimp on a thermostat when you know that it will not work ?

These were never cheap cars, and are still valuable enough to be cared for.

RT.
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Bob Livermore
New User
Username: livermoreb

Post Number: 7
Registered: 5-2007
Posted on Tuesday, 30 December, 2008 - 00:45:   Edit PostDelete PostView Post/Check IP

Richard

What makes you think it will not work? This is why I asked this question in the first place. I just think paying A$500+ for something that should cost a fraction of that is extortionate. I resent that and I don't think I am alone in doing so.

Somewhere along the line, someone took the thermostat out of my car. I don't know whether that was because it was overheating or if the thermostat was faulty and whoever took it out did not want to pay silly money for a replacement. Either way, I was concerned that the car never seemed to heat up and was trying to find a way to resolve that, hence my original posting.

If you know of a reason why the thermostat I have put in, which fits the housing perfectly and is the right temperature, will not work I would be very grateful for your advice.

I have often found that replacement parts exactly the same as the originals can be sourced more cheaply elsewhere. Recently I replaced the motor on the heater fan with an identical one from an Austin 1100 for a tiny fraction of the price being quoted for an RR replacement - both were made on the same production line by Smiths but the prices had been set to reflect the car they were destined for. There is even a website devoted to finding cheaper replacement parts for Rolls Royces at http://mutley.hypermart.net/RollsSubstituteParts.html
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Paul Yorke
Prolific User
Username: paul_yorke

Post Number: 260
Registered: 6-2006
Posted on Tuesday, 30 December, 2008 - 02:31:   Edit PostDelete PostView Post/Check IP

Now I'll start this by saying that I have never tried to fit a 'normal' cheap thermostat to a R-R 0r Bentley, and without deeply thinking about it, and seeing the results of it, I wouldn't consider it.

Richard is saying, why risk a $20k engine for 2% of it's value? I'm all for saving money, but there's saving money and there's gambling against the odds. I would gamble on a new R-R cloud thermostat lasting between 5 & 10 years. You have a temperature gauge so you can keep an eye on it. Thermostats are easy to test.

Martin starts by advising blocking the by-pass hose.

I thought that the whole idea of the bypass was to allow water to circulate around the head and block when the thermostat is closed?

I don't know what the thermostat you are thinking of fitting is like, but the R-R one is dual acting, opening the top hose and closing the by-pass. Also the bellows/wax area is quite low so they are in the flow of water.

So there's a few reasons. But like I say, I've never tried :-)

(Message edited by paul_yorke on 30 December 2008)
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1542
Registered: 4-2003
Posted on Tuesday, 30 December, 2008 - 04:27:   Edit PostDelete PostView Post/Check IP

Paul, spot on.

These motors are designed to have a healthy flow through the block at all times. Specifically, R-R did not design the coolant pump arrangement simply to cavitate when the thermostat is closed as on some cars, while others use tricks like a a simple restricted recirculation through the header tank as on my BMWs. Others have a pressure-varied valve or a pop-valve in the bypass circuit. You cannot rely on the heater matrix for flow as it is often closed off or cycled by the water tap even in winter.

Blocking the bypass defeats the functionality of the cooling system. It will generate hot-spots in the head and alloy cylinder block through lack of flow when cold. Also, with a blocked bypass and a cold thermostat, and therefore no flow past the thermostat, parts of the motor may boil unnoticed for a while while the thermostat remains cool. That has lead to coolant blow-off and diagnoses of blown head gaskets, when in fact the wrong thermostat is the only cause.

Leaving the bypass open with a single-action thermostat will give a coolant path of lower resistance when hot, bypassing the radiator and its long restricted circuit, the bypass restricted only a little by the narrower but very short bypass hose.

I have thought of putting a valve in the bypass (variable, pop or electrically operated, or even a thermostat), but then why not support the firms who support us with spares and do it properly ?

Take your BMW in for a minor service and I dare you to compare the prices. Too many people don't blat an eyelid at a $2,500 service on a VW V6, then whinge about spending a hundred bucks on Crewe parts.

Thank your lucky stars. You never need to budget for a new camshaft drive belt and idler at 40,000-80,000km: what does that cost on a Mazda or a BMW ? A darn sight more than a Crewe thermostat for parts alone.

I always equate parts costs to the cost of x tanks of fuel or y oil changes: drive from Sydney to Coff's Harbour and back for the weekend and the numbers stack up to the cost of a genuine part for this very special type of two-way thermostat. Risking an argument on oils, I use Mobil 1 5W50 (R-Type, T and Turbo R, and mandatory on many new cars) at a cost alone of at least $160 every six months or so for a change. Add on a filter and a bit of labour and you’ll see what I mean. I'll bet just a new tyre or two will cost about the same as this one, and tyres are safe for 5-7 years regardless of wear according to many.

Rant over.

Ps that substitute spares site you mention was listed on rrtechnical.info, but there were too many caveats noted, for example on oil pressure senders, so it was deleted. Take care. It is still on:
http://homepage.swissonline.ch/Richard_Treacy/substitutespares2008.pdf
but watch out as especially many of the oil filters and brake pads listed are dodgy.
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Bob Livermore
New User
Username: livermoreb

Post Number: 9
Registered: 5-2007
Posted on Tuesday, 30 December, 2008 - 22:00:   Edit PostDelete PostView Post/Check IP

Thanks for the full explanation guys. At least we all now understand the issues involved and the reason why the RR thermostat is so much more expensive than a normal one.

From the look of them on the Introcar web site, they are hand crafted in small numbers to do a unique (apart from Armstrong Siddeley) job. No wonder they are expensive, but there would appear to be no alternative - which is what I wanted to know.

Just as an aside, do you know what the difference is with the Silver Shadow, which is basically the same engine but I guess has a different design to the cooling system and thermostat?

Happy New Year

Bob Livermore
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1543
Registered: 4-2003
Posted on Wednesday, 31 December, 2008 - 00:08:   Edit PostDelete PostView Post/Check IP

The Silver Shadow and Silver Spirit (ie all SY and SZ cars) block the bypass aperture at the base of the thermostat housing. The thermostat has a disc which lowers in the housing to block the bypass route.

On earlier cars, MkVI, R-Type, S1, S2 and S3 cars, the bypass aperture is located at the side of the thermostat housing. The thermostat has an arrangement to block the bypass aperture at the side.

Note that MkVI, R-Type and S1 cars have the same thermostats. The S2 and S3 cars have different ones. On all MkVI, R-Type, S1, S2 and S3 cars, however, the thermostat must be oriented such that the thermostat blocking aperture is aligned with the housing aperture. Usually, this is determined by a marking FRONT on the thermostat. There is a special brass locating setscrew, also used as a bleed hole, which protrudes through the side of the housing into the housing.

Beware, as the locating setscrew is often sheared, removed or broken, especially where people have experimented with alternative thermostats. In that case, best replace the setscrew or retap the hole if necessary for an oversized setscrew with a trimmed end to fit the thermostat.

RT.
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Bob Livermore
New User
Username: livermoreb

Post Number: 10
Registered: 5-2007
Posted on Wednesday, 31 December, 2008 - 00:39:   Edit PostDelete PostView Post/Check IP

Thanks again - I'll look out for the set screw - I never noticed it when I looked before.

Bob Livermore
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Martin Cutler
Prolific User
Username: martin_cutler

Post Number: 103
Registered: 7-2007
Posted on Saturday, 03 January, 2009 - 18:35:   Edit PostDelete PostView Post/Check IP

?????????????

Quote from above - Blocking the bypass defeats the functionality of the cooling system. It will generate hot-spots in the head and alloy cylinder block through lack of flow when cold. Also, with a blocked bypass and a cold thermostat, and therefore no flow past the thermostat, parts of the motor may boil unnoticed for a while while the thermostat remains cool. That has lead to coolant blow-off and diagnoses of blown head gaskets, when in fact the wrong thermostat is the only cause.

???????????????????????????????

The original thermostat blocks off the bypass! Totally! That is why the modern thermostat has a small hole in it to allow the water to circulate. The MK VI / R type also has 2 small holes in the front of the block to allow water to circulate and stop cavitation.

My MK VI has 12 years and 14000 miles on a modern thermostat. My other MK VI also has a modern thermostat. The R Type I am restoring, (with the still stuck head) was running no thermostat at all, that is a worry. The coolant I use (Penrite Classic Car Coolant), unlike glycol reduces the surface tension of the water, stopping hots spots and air pockets.

I think I would rather spend my money on good red wine richard......
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1554
Registered: 4-2003
Posted on Saturday, 03 January, 2009 - 21:14:   Edit PostDelete PostView Post/Check IP

Er.. perhaps a re-read is due on hot spots and the like, or do I need to spell it out further ? The bypass only starts to block as the thermostat starts to open when you start to need more than a sea breeze over the sump for cooling. The bypass is fully open when the coolant is cool. You may be lucky and get away with a poor thermostat for short trips and for pottering around at less than 60mph, but not in anything but mild conditions. I wouldn't like your chances at 90mph (sorry, cops, 70MPH) for hours across the Hay Plains. I don't think that an R-Type with a head still stuck after all this time is exactly a good reference. As for reducing surface tension, that's rather like pushing something brown uphill with a pointy stick. Better spend the dosh on a proper thermostat than on snake oil.

RT.
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Laurie Fox
Experienced User
Username: laurie_fox

Post Number: 48
Registered: 6-2004
Posted on Sunday, 04 January, 2009 - 02:57:   Edit PostDelete PostView Post/Check IP

Is there a bleed hole in the SC3 thermostat which allows trapped air to escape?

Is it a recommendation that these thermostats be changed every 5 years and if so why?

Do these thermostats have any provision for removing then wthout damage for testing, like the bellows type on MK VI etc.?

Regards

Laurie

(Message edited by laurie_fox on 04 January 2009)
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Laurie Fox
Experienced User
Username: laurie_fox

Post Number: 49
Registered: 6-2004
Posted on Sunday, 04 January, 2009 - 05:41:   Edit PostDelete PostView Post/Check IP

Martin says:-

The MK VI / R type also has 2 small holes in the front of the block to allow water to circulate and stop cavitation.

I don't think that these holes have anything to do with cavitation in the pump. My understanding is that they are drain holes to ensure that no coolant remains in the pump body when the system is drained. Pictures of corroded and new parts are at http://www.bdcl.org/forum/viewtopic.php?p=4039

Regards

Laurie
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 1556
Registered: 4-2003
Posted on Sunday, 04 January, 2009 - 06:48:   Edit PostDelete PostView Post/Check IP

12 years and 14,000 miles ? That's less than a hearse on sabbatical.
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Martin Cutler
Prolific User
Username: martin_cutler

Post Number: 104
Registered: 7-2007
Posted on Sunday, 04 January, 2009 - 13:20:   Edit PostDelete PostView Post/Check IP

sorry Richard, typo, 24,000 miles. The arguement I think you are putting forward is that lack of flow during the warm up period will lead to hot spots. I have opened up the bleed hole a bit larger than standard, which allows a bit more flow when cold.

Marty

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