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  View original topic: hot running temps + inop aux fan post thermostat replacement
jwendorf Thu Nov 10, 2016 11:57 am

On Monday my wife told me the heat was not coming on in our van ('89 carat). I took the van for a drive and determined that the heat was indeed not coming on, i.e. at normal running temp (half way up the temp gauge) there was no hint of heat coming out of the front heater.

After driving for ~10 minutes the heat all of sudden came on, so my thought was that the thermostat was sticking. I headed down to the FLAPS, bought a thermostat and replaced it next morning.

Since replacing the thermostat the heat starts blowing warm after a few minutes of driving, however I have noticed that the van is taking a lot longer to get to operating temp, i.e. it took 10 minutes of driving this morning before the temp gauge reached the mid-way point. But after the temp gauge hits mid-way it continues to creep up to almost the top of the temp gauge. If I run the front and rear heater fans the temp drops a bit, also if I'm moving it drops a bit, but stays in the top quarter of the temp gauge.

Additionally, the aux fan is not coming on as it presumably should when the temps are getting high. I tested the fan with a jumper wire at the radiator switch and confirmed that both fan speeds are working. I then replaced the fan switch in the radiator. Still the fan is not coming on.

Last night I spent some more time bleeding the system and while bleeding it the aux fan kicked on a few times. However after driving the van today the engine temp gauge was still really high and the aux fan never kicked on.

Since the engine is taking a long time to get to operating temp (at least compared to the few minutes it took prior to replacing the thermostat) my thought is that the new thermostat is opening too soon. However that doesn't seem to mix with the fact that the operating temps are climbing too high after replacing the thermostat.

Is it possible that I still have air in the system that is blocking the circulation to the radiator which is causing the radiator to not get hot enough to cause the aux fan to kick on? Or something more concerning?

dobryan Thu Nov 10, 2016 11:59 am

Did you test the new thermostat in a pot of water under heat before installing it? Some are not good right out of the box.

wesitarz Thu Nov 10, 2016 6:20 pm

I had similar symptoms (rising temp at engine with no rad fan in stop and go city traffic,temp comes down if moving,temp down with heat on). Had a new rad. It wasn't the thermostat,fan switch or even the water pump. It was the blue expansion tank cap.
How old is your blue cap and rad? Replace expansion cap (cheap), replace rad (expensive). Assuming you are bleeding it well (still might be air)
If you have the heat on it takes longer to reach operating temp.

88 Wolfsburg auto Carat with 02 Subaru 2.5L

pablum Thu Nov 10, 2016 11:02 pm

I doesn't sound like you noticed any difference between the old and new tstats.
Like the size of that pancake part.
My flaps gave me one like that.
It wouldn't open, naturally enough.



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