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Sat Jul 02, 2022 2:11 pm

Driving around in the ungodly 70 degree heat yesterday and my cooling fan came on after a lengthy stop at a light. Once I peeled myself off the dome, it quit due to the airflow. Happened again and I was able to eliminate the cycle by turning on my no-op A/C which turns the fan on low full time.

New water pump last year, coolant level is good (occasional red light on the dash at startup but it passes), oil cooler w good oil/water temps, and reasonable ambient temps… am I right to suspect the radiator might not be doing its job? I have replaced the thermistor but if the flow is bad, that might not have helped.

I don't know if there is a test (maybe an IR meter across the face of after warmup?) or if I just bite the bullet and swap one in? Not something I am looking forward to but maybe it's time. Could be the original equipment up there, for all I know.

Any further tests to narrow things down?

Sat Jul 02, 2022 2:38 pm

That's the way it's supposed to work. There is nothing wrong.

Duncan

Sat Jul 02, 2022 7:13 pm

DuncanS wrote: That's the way it's supposed to work. There is nothing wrong.

Duncan

+1

The air flow though the radiator allows heat to leave the coolant. Air flow is obtained by moving the van's radiator through the air (by driving), or by moving air through the van's radiator (with a fan).

Sat Jul 02, 2022 8:26 pm

Yep, sounds like things are doing what they're supposed to.

I stressed tested my cooling system for the first time a couple weeks ago while sitting in a very slow moving line of cars at the waste transfer station in 70*F+ heat (very warm for Anchorage btw) for about 45 minutes. I have an aftermarket water temp gauge so I watched as it climbed to 210ish and then heard the cooling fan kick on and saw temp ease back down to 200 and sorta stabilized. Fun fact, if everything is truly working like it should, if the coolant in the radiator is above the critical temp (I forget what that is exactly) the fan will stay on even after the engine is turned off.

Sun Jul 03, 2022 1:51 am

TomInAlaska wrote: If everything is truly working like it should, if the coolant in the radiator is above the critical temp the fan will stay on even after the engine is turned off.

Happens to me all the time. Fan is running for a couple of minutes after I get out of the car.

Duncan

Sun Jul 03, 2022 3:00 am

If you take those IR measurements on various positions of the radiator now while it is working correctly, you have a benchmark to test against later.

Or, one can replace coolant every 30k and not plug up the radiator.

Sun Jul 03, 2022 3:13 am

Abscate wrote:
Or, one can replace coolant every 30k and not plug up the radiator.
Nothing I need to worry about with my frequent total coolant losses--see latest "The Last Straw". https://www.thesamba.com/vw/forum/viewtopic.php?t=766705&highlight=