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Chris
Chris, Auto Service Technician
Category: Car
Satisfied Customers: 13137
Experience:  43 years of automotive repair, Smog license
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Ok, so my little 92 subaru legacy - that has NEVER run hot

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Ok, so my little '92 subaru legacy - that has NEVER run hot - has now done it twice! both times after about a 5 hr on-the-road trip - last night, I stopped for gas and then, as I was pulling out of the gas station, saw that the CHECK ENGINE light was a steady, bright red and that the temp gauge was inching past the 3/4 mark! I immediately stopped and let it cool down - I also opened the hood, saw that there was no excess fluid in the radiator overfil thing and, oddly enough, the radiator was not even hot to the touch!!! Sooo, I carefully undid the radiator cap - no steam, nada! it did appear a bit low on antifreeze - even though I had just had the radiator flushed and new fluid put in - along w/other work - replaced the valve cover gaskets, the oil pan gaskets, changed the oil, new oil filter/air filter, fuel filter and spark plugs - plus a new thermostat!!! The mechanic told me that I didn't even HAVE a thermostat in the car! That it, awa the vcg were held together w/silicon!!!!

So, my son - in Australia, I might add - I was in Pomona CA - told me to turn on the HEATER and run it full bore and drive only 55mph to get home - which I did - it worked! However, I tried some things just to see what would happen - when i turned the heater off - slid the temp bar down to the blue side, the CHECK ENGINE light immediately came on! When I slid it up to the RED [right] side, it immediately went off and stayed off!!! Also, the fans came on when the heater was on - not so much when the AC was on - [the car wasn't moving when I checked this]...

So my question is - WTH is the deal??? How can a car's radiator NOT be hot or steaming and yet the temp gauge register hot??? Could it be a sensor? Wiring of some sort - I have had wiring issues w/this baby before, btw - the engine has 202000 miles on it - low for a subaru - and I really need to keep if for another 6 months at least! Help!!!

Hello and welcome to just answer. Was the radiator warm at all or cold?

Chris

Customer: replied 4 years ago.

It was cold!

Ok if the heater was hot, but the radiator cold, then that tells me the coolant was not flowing through the radiator, but was flowing through the heater core. That tells me the water pump is working, and the reason coolant was not flowing through the radiator is 1 a stuck closed thermostat, or 2 a plugged radiator. Now you said that the thermostat was replaced so either it is a defective one, or you have a blockage in the radiator. I recommend redoing that thermostat first (maybe your mechanic will do that under warranty). If the problem persists after replacing the thermostat then replace the radiator.

I hope this information helps you, and let me know if you need further assistance with this,

Chris

Customer: replied 4 years ago.

Waaa! I had it done in Algodones Mexico because I had to get home! Also, why would it be a little low on fluid and not "over heat" until I drove - with the AC on - for 250 miles???

Hmmm, It may be an intermittent thermostat issue, or the other thing it could be is a cylinder head gasket that is leaking just a little. This could cause combustion gas's to get into the cooling system and cause flow problems. So, at this point, have a shop do a "block check" with a chemical cooling system block checker. If it fails the test, then the heads will need to be pulled and inspected. Now if it does pass the test, then go with the thermostat/radiator recommendation. One more idea I just thought of: If you find out that there is a leaking head gasket, and you are getting rid of the car in 6 months, try a bottle of Blue Devil head gasket sealer. I have used this product before, and it works. Here is a link their web site.

Chris

http://www.gobluedevil.com/

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