| Author | Message | ||
     David Towers Frequent User Username: xtriple Post Number: 55 Registered: 6-2010 |
My car, like most I suppose has a viscous engine driven fan and two electric ones in front of the radiator. My questions is: when do these two electric fans operate? My engine was at the usual temperature, the air con was nice and cold (warm here today for a flippin' change!) and during the minute or so I was looking the fans did not operate (engine was idling at the time. Car is chassis 66221. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1538 Registered: 6-2006 |
Hi David, they only come on when the engine is threatening to overheat or the air con system gets very high. It is more usual for them never to come on. | ||
| David Towers Frequent User Username: xtriple Post Number: 56 Registered: 6-2010 |
Thank you. Paranoia about this car is NEVER far away. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1539 Registered: 6-2006 |
Always better safe than sorry  | ||
| michael vass Prolific User Username: mikebentleyturbo2 Post Number: 171 Registered: 7-2015 |
Hi David If you want to check them just short out the auxiliary fans relay . Mike | ||
| David Towers Frequent User Username: xtriple Post Number: 57 Registered: 6-2010 |
Hi David If you want to check them just short out the auxiliary fans relay . Mike Mike, with the best will in the world and I know you are being helpful, but the chances of me touching the wiring in this car are about as remote as me winning the lottery! If I did what you suggest I am sure the thing would spontaneously combust and I would be left with nothing but an empty bank account and scorched tarmac Seriously though, thanks for the help everyone - you guys know all there is to know about all things RR and B. It is amusing how often on other forums this one is recommended for help, advice, knowledge base etc. You chaps are all famous! | ||
| Darryl Watson New User Username: inox Post Number: 10 Registered: 4-2015 |
Hi Paul, Re your post above: "It is more usual for them never to come on". The fans on my 1990 Mulsanne S fairly often come on after a run now that our (English) summer has arrived. I fitted a new switch obtained from Heaven's Gate in Germany. Do you think I should be overly concerned?. The temp gauge sits in the white. Regards Darryl | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1573 Registered: 6-2006 |
Hi Darryl, Is the viscous coupling locking up when hot? As long as the gauge is central and there is no water loss I wouldn't be concerned. Perhaps the switch is set a little lower. Not a bad thing really. These big engines soak up a lot of heat when driven fast or hard. I always try to give them a cooling down period for a few miles before stopping. Not always easy when you suddenly hit standstill traffic though. | ||
| Darryl Watson Experienced User Username: inox Post Number: 11 Registered: 4-2015 |
Thanks Paul, I will check the VC next time I clock up a few miles. We are surrounded by 20mph speed limits near my home so the engine doesn't do much work for last few miles. Regards Darryl | ||
| Christian S. Hansen Grand Master Username: enquiring_mind Post Number: 314 Registered: 4-2015 |
Notes from the peanut gallery... Darryl...My own preference would be better for the fans to come on, even if prematurely, in order to keep the engine cool and to let you know that they are working, than to not come on at all, or only after the engine coolant has exceeded it expected operating temperature and the fans are attempting to assist with "getting things back under control." I can however see a concern that the fans turning on may indicate that the engine coolant is running too hot, rather than the "cut in" temperature being too low. The best and only really reliable way of testing this IMHO is to get a quality ($40-$50) infrared heat gun and use it to check and monitor your heat circumstances and it can also let you know at what temperature the fans are actually turning on and then decide if they are cutting in before they are needed, which is better than too long after they are needed. As to the viscous coupling, I have recently gone through a lot of angst regarding their function and should note that they do not actually "lock up" in the way that term implies...as in a manual transmission being put into gear, or the manual bell housing clutch engaging, locking up, not slipping, when you remove your foot from the pedal. Nor is it like a light bulb that is either on or off. It is more akin to your coolant thermostat that slowly opens and is variable between its closed position and its open position. That variation is controlled by the specifications of the bimetal coil as to at which temperature it begins to move and at what temperature it is fully opening the clutch valve. If you ever have a viscous coupling on the bench you can test and observe this action with a 1500watt hair dryer and that handy IR heat gun. I have done exactly that experiment recently and was surprised that one VC (for a Jaguar) began to open at only 120F (!) but yet was not fully open until closer to 210F, whereas another VC (the Hayden 2747) for a different application (RR) did not begin to open until about 200F and even the maximum heat I was able to generate with the hair dryer (245F) did not seem to cause the valve to be fully open. My suspicion is that you will find that all is well temperature wise and the coolant fans simply come on at a lower temmperature than you would have expected, or desired. Have fun! | ||
| Darryl Watson Experienced User Username: inox Post Number: 12 Registered: 4-2015 |
Thanks for the detailed post Christian. Very informative & interesting. Regards Darryl | ||
| Martin Taylor Experienced User Username: martin_taylor Post Number: 21 Registered: 7-2013 |
It is worth noting that should your radiator be partially blocked or your thermostat stuck closed the viscous fan will appear to be faulty as the heat required to activate the bi-metal is not not getting to it | ||
| Christian S. Hansen Grand Master Username: enquiring_mind Post Number: 317 Registered: 4-2015 |
I suspect that if one's radiator is partially blocked, or the thermostat stuck closed, the engine will be either prone to overheating, or will be already vigorously overheating, and in terms of the suspected causes for that overheating, the fan clutch will probably be rather far down on the list of possible problems. The things that will be checked and/or addressed first are typically the thermostat and the radiator and probelm will be resolved without turning to the fan clutch. That said, I do agree that the "Achilles Heal" of the bimetal engagement mechanism of the fan clutch is that it relies on heat to activate, and since it does not activate based on heat from coolant temperature, but rather the temperature of the ambient surrounding air and presumably passing thru the radiator to generate that heat, IMHO the triggering mechanism to engage it is more remote than it could be were it sensing coolant temperature, rather than air temperature. Accordingly, the idea of an electrically operated fan clutch that engages based on sensing coolant temperature is therefore an improvement on that triggering mechanism, again IMHO. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1580 Registered: 6-2006 |
You have to look at all 3 . Rad . Thermostat. Viscous. Plus the temperature gauge and sender. Feel across the width of the rad to check water is flowing down all the vanes. Christian. It's simplicity is also it's beauty. Only cools when hot air is coming through the rad. Saves energy etc on cold days when the engine is hot but air is cold. | ||
| Christian S. Hansen Grand Master Username: enquiring_mind Post Number: 319 Registered: 4-2015 |
Hmmm...I guess I'm just not getting it. Seems to me that if the engine is hot, but the air is not, that is the precise time I would like the fan to be on, rather than off, as I would like to cool the engine down. | ||
| michael vass Prolific User Username: mikebentleyturbo2 Post Number: 210 Registered: 7-2015 |
Hi Christian Yes your right but by then the thermostat should be open and hot air should be blowing over the VC ok Mike | ||
| Larry Halpert Experienced User Username: larry_halpert Post Number: 187 Registered: 09-2003 |
"If you want to check them just short out the auxiliary fans relay. Mike" Hi Mike, Which two pins do you short out to send power to the fans (when looking at the relay or socket) Which specific pin sends power to the fans? (also, when looking at the relay or socket) - Larry | ||
| michael vass Frequent User Username: mikebentleyturbo2 Post Number: 710 Registered: 07-2015 |
Hi Larry An easier way is short the switch which sits on top of the thermostat housing ok, you need the ign on too. Cheers Mike |
