Not another overheating question...

[misak1914]

Greetings all.

I've been a fan of this forum for years and have not had a reason to post questions; mainly because most of the issues I've had seem to have been answered 10-20 times in previous posts.

However, here are my scenario/questions: I have a 87 944 that is overheating, and my fans are not coming on unless my AC switch is in the on position. I replaced my thermostat with a stock 180 degrees F thermostat; next I am replacing my thermo fan switch. Here's my question, what temperature thermo fan switch do I need to get? Pelican has 75 & 85/93 degrees C switches. I'm not sure if the switch needs to be at a lower or higher temperature than the thermostat. Can someone explain this to me?

Also, why would someone want to install a thermostat with a lower or higher temperature rating than what the OEM calls for? I assume it has something to do with if the driver is either racing or in a colder temperature.

Lastly, which antifreeze mixture is recommended 50/50 or 70/30?

Thanks for your help

[Techno Duck]

Personally i would run the 85/93 fan switch. This is one range colder than the stock switch (95/103). With the stock range switch i see temperatures in the 215+ range sitting in NYC traffic on a relativley warm spring day. They will get even higher than that in the dead of summer. This is still well within spec but at the higher end the spectrum in my opinion. With the 85/93, i have yet to see over 200 degrees. I went through this a few weeks ago when the switch on my car went bad. It was a friday afternoon and i was doing a track event that weekend. My friend ordered the switch through his shop account and 30 minutes later i had it in my hand. I thought i had the stock range which was the 95/103, but i ended up having the 85/93 (was replaced by one of the PO's). So i ran the switch that weekend and was not happy with the temps.. i was seeing consistently over 210* sitting in traffic on the way to and from.. and my oil temps as a result were also about 10* higher than usual. I replaced it with a new 85/93 and all is well again. Basically unless you live somewhere where it is very cold year around, i would run the 85/93.

Usually you will want to install the lower temp switch if you live in a relativley warm area to help keep those peak temperatures down. One thing that never made sense to me is people saying they install different temp switches to stop the fans from cycling on often as you would need to increase the temp range on the fan switch to do this... not lower it. Anyhow, by putting in a lower temp switch, you are effectivley lowering the peak temperature the cooling system will see. Besides, who care if the fans cycle on more often, they are cheaper than an over heated car or stressing the heck out of the head gasket.

For coolant mix, i would simply do 50/50.

[misak1914]

Exactly the info I needed. Thanks Techno Duck!