darennoc Posted May 21, 2009 Share Posted May 21, 2009 Engine Cooling problem 2000 Subaru Legacy 4 cyl Four Wheel Drive Manual 25000 miles Vehicle usually runs with temp gauge always midway. Recently, in stop and go traffic the gauge will quickly creep up close to the high mark. If I turn on the AC, the temp rapidly drops back to midrange. Fluid levels are constant and fine. Heater works so presumably the thermostat can open. There are no codes reported on the dash. Turning on AC turns on both cooling fans so both fans can work - probably why this cools the system down There is no bubbling in the overflow or loss of coolant or white smoke. I am thinking that one or both of the cooling fans are not turning on at the appropriate temperature. What should I check? The problem has happened several times but it is not consistent. The car usually has to be running for quite a while before the temp shoots up and it is only a problem at idle not while the car is moving. Thank you Link to comment Share on other sites More sharing options...
whitetiger Posted May 21, 2009 Share Posted May 21, 2009 sounds like the fan which is supposed to click on to circulate air, not the ac fan, is not working. at ide, even if the ac is off, one one of the radiator fans shoulc come on when the coolant reaches a certian temp. if this fan does not come one, the car will slowly begin to overheat since ther is no airflow over the radiator at idle. Link to comment Share on other sites More sharing options...
darennoc Posted May 21, 2009 Author Share Posted May 21, 2009 Thanks for the response, So I know both fans work since they both kick in with the A/C. What is the likely component that is preventing the main fan from turning on when the temp gets to a certain level - coolant temp sensor? Could this be a relay failure even though the fan actually works or possibly an ECM problem? Any suggestions on how to diagnose the location of the failure. Thank you Link to comment Share on other sites More sharing options...
whitetiger Posted May 22, 2009 Share Posted May 22, 2009 could be any of the things you mentioned. id try to find a circuit diagram of the circuit in question. it will help you trace the problem out. id start witht he relay first sice its easiest to check and replace. Link to comment Share on other sites More sharing options...
GreenLeggy Posted May 26, 2009 Share Posted May 26, 2009 Well, if your fan comes on, then the relay is working. Your best bet would be to checke for a fouled temp sensor or even a stuck thermostat. Do Subies use thermostats in their radiators? I'm sure they do...in any case, a stuck thremostat will not open/close, allowing for the coolant to flow at the proper/pre-set temperature. The thremostat is usually located at the top of the radiator. The one little cap that says DO NOT OPEN WHEN HOT! I hope this helps...I had the same issue happen to me with my honda...the thermostat was stuck. Juan Link to comment Share on other sites More sharing options...
Pdizzleccc Posted May 27, 2009 Share Posted May 27, 2009 Listen for the fans to come on without the ac on, if they don't then you probably have a bad temp sensor somewhere, that is what turns the fan on and off in traffic, search for a wiring diagram to locate the sensor... Link to comment Share on other sites More sharing options...
subaruowner Posted July 2, 2009 Share Posted July 2, 2009 Hi everyone, I am a newbie and just found these forums. Great info! I have been experiencing some similar issues with my 2006 Legacy I. It only has 85K mi on it, and my mechanic cant find any issues with the cooling system. The fan comes on like it should, but the temp still rises in traffic and when climbing a hill. Possible radiator clog that the flushing would not have found? One thing that is different about my car is that I have two fans, but: One fan (the driver's left) comes on for cooling One fan comes on for the ac. Ac does not run both fans. Any and all help is beyond appreciated. Thanks. Link to comment Share on other sites More sharing options...
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