928 running very hot - please help
02-19-2005, 06:08 PM
#16
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Ebs- you need to give us a little more information. Does your car run hot when sitting in traffic, yet keep its cool when you are in steady cruise, or does it run hot all the time?
If it runs hot on some days but not on others it could be a sticking thermostat or possibly a bad water temperature gauge, most likely the later.
N!
If it runs hot on some days but not on others it could be a sticking thermostat or possibly a bad water temperature gauge, most likely the later.
N!
02-19-2005, 06:32 PM
#17
Rennlist Member
On another car I had a guage temp sender problem that drove me nuts and cost me $$. The guage showed the car was overheating even after I threw a bunch of new parts at it. Finally I took the pressure cap off and used a lab thermometer to check the temp of the overflow stream to the coolant bottle. It was perfect. Replaced the temp sender and the problem went away.
BTW, on that car there were two senders, one to the guage in the cockpit and the other to the fuel ECU.
A quick and dirty test of your viscous clutch is to try to stop the fan when the engine's at op temp. If you can the clutch is bad. Obviously, neither your hand nor a stout stick is the right stopper for this experiment. I have used a broom. It's soft, pliable and non-damaging.
On that other car I mentioned I ended up making an adapter for a $20 clutch from the auto parts emporium, rather than buy a $250 (iirc) clutch.
BTW, a pressure cap that's gone South (if that phrase in this context is offensive to you antipodeans, I apologize) will also cause an overheating situation, a real one. BTDT
BTW, on that car there were two senders, one to the guage in the cockpit and the other to the fuel ECU.
A quick and dirty test of your viscous clutch is to try to stop the fan when the engine's at op temp. If you can the clutch is bad. Obviously, neither your hand nor a stout stick is the right stopper for this experiment. I have used a broom. It's soft, pliable and non-damaging.
On that other car I mentioned I ended up making an adapter for a $20 clutch from the auto parts emporium, rather than buy a $250 (iirc) clutch.
BTW, a pressure cap that's gone South (if that phrase in this context is offensive to you antipodeans, I apologize) will also cause an overheating situation, a real one. BTDT
02-19-2005, 07:02 PM
#18
Burning Brakes
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Hi,
as Wally, I and others have said - determine first if the "problem" is real!
I agree with Wally on the use of IR readers having used them extensively and the following data will give you an insight as to what "normal" readings are (discounting the wobbling gauges etc)
These are the averages of 120 readings for a fully warmed up engine (after at least 30 minutes on road) taken over two years
Highest shown ( ) and median as [ ] and all +/- 2C
At mid point on valve covers = 89C (98C) [88C]
At temp sensor in vee = 88C (95C) [88C]
At metal cover return to thermostat = 86C (92C) [86C]
At top hose close to radiator = 73C (88C) [74C]
At bottom hose half way up vertical section = 76C (90C) [76C]
Oil cooler top = 75C (88C) [75C]
Oil cooler bottom = 77C (90C) [77C]
If all of these are (collectively) below 100C you will most likely NOT have a cooling system overheating problem. Then you will need to check the sensors, senders and gauge
If any individual reading is higher than 100C it will provide a basis for further diagnosis
Remember that these engines are intended to run HOT! The intended "core" temperature is around 91C-96C
The coolant thermostat opens at 83C(+/-2) and is fully open at 98C(+/-2)
The oil cooler thermostat opens at 87C and is most likely fully open at around 93C
I suspect that the greatest problem with these engines is to run them too COLD!
You know that the area where I live in OZ is very HOT all year round and HUMID for at least three months. Highest well over 42C and humidity up to 95% - it is 37C and 88% today!
Do not be disuaded from attending to the viscous fan if it is faulty - when working well these are excellent at their intended task - perhaps better than electric fans!
Regards
as Wally, I and others have said - determine first if the "problem" is real!
I agree with Wally on the use of IR readers having used them extensively and the following data will give you an insight as to what "normal" readings are (discounting the wobbling gauges etc)
These are the averages of 120 readings for a fully warmed up engine (after at least 30 minutes on road) taken over two years
Highest shown ( ) and median as [ ] and all +/- 2C
At mid point on valve covers = 89C (98C) [88C]
At temp sensor in vee = 88C (95C) [88C]
At metal cover return to thermostat = 86C (92C) [86C]
At top hose close to radiator = 73C (88C) [74C]
At bottom hose half way up vertical section = 76C (90C) [76C]
Oil cooler top = 75C (88C) [75C]
Oil cooler bottom = 77C (90C) [77C]
If all of these are (collectively) below 100C you will most likely NOT have a cooling system overheating problem. Then you will need to check the sensors, senders and gauge
If any individual reading is higher than 100C it will provide a basis for further diagnosis
Remember that these engines are intended to run HOT! The intended "core" temperature is around 91C-96C
The coolant thermostat opens at 83C(+/-2) and is fully open at 98C(+/-2)
The oil cooler thermostat opens at 87C and is most likely fully open at around 93C
I suspect that the greatest problem with these engines is to run them too COLD!
You know that the area where I live in OZ is very HOT all year round and HUMID for at least three months. Highest well over 42C and humidity up to 95% - it is 37C and 88% today!
Do not be disuaded from attending to the viscous fan if it is faulty - when working well these are excellent at their intended task - perhaps better than electric fans!
Regards
02-19-2005, 11:46 PM
#19
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Thanks again to all of you. Looks like I have some homework to do now 
The car seems to get hot in traffic or while running - it makes no difference. If my 951 gets hot in traffic a sustained period of running, especially on the freeway, cools it right down and quite quickly. The shark temp guage never seems to go down much, it usually stays constant or now it tends to just go up.
The car seems to get hot in traffic or while running - it makes no difference. If my 951 gets hot in traffic a sustained period of running, especially on the freeway, cools it right down and quite quickly. The shark temp guage never seems to go down much, it usually stays constant or now it tends to just go up.
02-21-2005, 10:47 AM
#21
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Running Hot
I went through the drill a yeaqr ago: flushed radiator, replaced radiator, thermostat, hoses. Turned out to be the fan clutch. It is deceptive because it will spin and look like it is OK when in fact it will not produce enough cooling air at engine speed. With new viscous clutch temp went back to normal.
02-21-2005, 10:49 AM
#22
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Running Hot
I went through the drill a yeaqr ago: flushed radiator, replaced radiator, thermostat, hoses. Turned out to be the fan clutch. It is deceptive because it will spin and look like it is OK when in fact it will not produce enough cooling air at engine speed. With new viscous clutch temp went back to normal. There is a way to replace the silicon but I decided not to fool around anymore and just get a new one.
Oliver Moore
85.5 928S
930
944S2
914
Oliver Moore
85.5 928S
930
944S2
914
