I have seen the phenomena you describe, though not on a Porsche, but have heard of the same applying to a 944... that is the water pump impellor becoming loose on the shaft. at low revs it doesn't spin/pump water, at higher revs drag is sufficient to overcome the resitance of the water and pump it round a bit. Tends to be variable, because sometimes it grips, sometimes it doesn't. I guess the same effect could be achived by insufficent belt tension (be scared!), oil on the back of the belt, or a water pump seizing up...
Running a bit warm - Thermo, Rad or Waterpump?
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scam75
Well-known member
Evening chaps
My car started running quite warm a couple of weeks back all of a sudden. It would normally sit just above the first white line under normal driving conditions then i noticed it moving up to the second line and pretty much staying there. If I revved it quite hard the temp would drop back to about half and then return close to the second line at idle or normal driving. The fans would come on but were unable to knock the temp back, only revving above 3k would cause the temp to drop.
Was thinking thermostat although new one only been in a few months. I ran it without a thermo for a day or so and it ran super cool. I have since put another stat in and it's doing the same as before although not just as hot.
It will occasionally drop down to it's previous normal position and then creep back up spending most of it's life between half way and the second mark. Again fans seem unable to knock back the temp and this time revving hard isn't as effective as before?
I'm sure it's bled properly, heaters are red hot. I've changed the temp gauge too but it read exact same as the old one. I'm convinced the temp reading is accurate as fan kicks in where it has always done.
Interestingly on the last journey I done before taking out the first suspect stat the car behaved perfectly normally. Could it be another duff stat? Both items were QH ones, 80 degrees, although rad seems to be getting hot when it should with this stat whereas I think it was cold with the first one. Confused![&:]
Any ideas?
Stuart
My car started running quite warm a couple of weeks back all of a sudden. It would normally sit just above the first white line under normal driving conditions then i noticed it moving up to the second line and pretty much staying there. If I revved it quite hard the temp would drop back to about half and then return close to the second line at idle or normal driving. The fans would come on but were unable to knock the temp back, only revving above 3k would cause the temp to drop.
Was thinking thermostat although new one only been in a few months. I ran it without a thermo for a day or so and it ran super cool. I have since put another stat in and it's doing the same as before although not just as hot.
It will occasionally drop down to it's previous normal position and then creep back up spending most of it's life between half way and the second mark. Again fans seem unable to knock back the temp and this time revving hard isn't as effective as before?
I'm sure it's bled properly, heaters are red hot. I've changed the temp gauge too but it read exact same as the old one. I'm convinced the temp reading is accurate as fan kicks in where it has always done.
Interestingly on the last journey I done before taking out the first suspect stat the car behaved perfectly normally. Could it be another duff stat? Both items were QH ones, 80 degrees, although rad seems to be getting hot when it should with this stat whereas I think it was cold with the first one. Confused![&:]
Any ideas?
Stuart
scam75
Well-known member
Okay, had another play with it tonight to make sure it was bled properly. Fairly convinced it is. I have noticed that the pipe which leaves the water pump to go into the bottom of the radiator is not particularly warm at the bottom although the top of the radiator feels quite warm as it should. I let it idle after going for a blast and the temp stayed just below the 2nd line with the fans on. I then pushed the demister button and the temp dropped down to a fraction over half way pretty quickly. This would tell me that I am getting decent flow but just not through the main radiator. I am not convinced that this second QH thermo is working properly. That pipe really should be as hot at the bottom as it is at the top shouldn't it when the temp is at the 2nd line? I think I will get a thermo from Porsche tomorrow before I go condemning the water pump. Thoughts? Stuart
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