Hello everyone. I am having a very tricky issue. Most of the time, my Legacy's temperature gauge reads dead center. Lately, though it has had intermittent overheating issues. If I drive it for a long time at freeway speeds and then hit stop-and-go traffic, I experience it. The other day I drove it 40 miles on the freeway to work no problem. I didn't drive it again until the evening, when I drove it the 40 miles home, about 82 deg. outside. I was running the AC. No problem on the way home either. It sat for about 20 minutes and then back in the car in stop-and-go traffic, freeway, and stop-and-go again. Then it began to overheat and actually went all the way into the red and the coolant overflowed onto the ground. Pulled over immediately, turned it off. Started it up again after a short period and ran the heater and the temperature was fine.

 

I took it into the shop and they kept it for a week and couldn't make it overheat. I got it back and went through almost the exact same scenario that same day and it overheated again.

 

Here are some details on the car:

2001 Subaru Legacy GT

174k miles

Head gasket replaced at ~90k miles

Thermostat is only around a year old.

Can't remember if the water pump has been replaced or not. If it has, it was a long time ago.

 

I talked with some people about it and they were wondering if maybe the air conditioner compressor is attached to the same belt as the water pump and if the water pump was not working optimally, if having the air conditioner on when running it hard could cause the issue. Any help is greatly appreciated.

 

Thanks!

when it's overheating do you get hot air if you turned the heat on - obviously it should be blazing hot given the overheating.

 

Subaru or aftermarket headgasket?

Subaru or aftermarket tstat (aftermarkets are visibly weak).

 

stop and go overheating suggests an air flow issue. when it gets hot again with the a/c on you need to make sure both radiator fans are kicking on.

 

fan failure or relay seems most likely.

 

it's possible the radiator is partially clogged as well. they're only $90 or so (or the 2000 Forester one i bought last year was anyway) from radiatorbarn.com and super easy to replace. only two bolts actually hold the radiator in place - other than that you just remove the fans first. 4 10mm bolts for each fan, disconnect wire plug for each fan, two bolts for overflow tank, then two radiator bolts up top and the thing just sits in grommets on two pegs at the base so it easily pulls right out.

my experience with clogged radiators though suggests overheating over high loads - like HOT outside, a/c on and temperature gauge climbs when going up a hill, goes down when going down hill - it can't keep up with the extra demand. it's usually very predictable like that - based on temps and load (a/c, hills, accelerating).

 

this engine also requires Subaru's coolant conditioner. if it wasn't added when the thermostat was done last year or you don't know, add another bottle.

stupid question:

 

are the radiator fans turning on?

Hey Guys,

 

Thanks very much for responding.

 

grossgary: Very hot air blowing out with the heater on. The head gaskets and tstat were both done at a Subaru dealer, so I am guessing they are official. The last mechanic to do the work was not a Subaru dealer, they just claim to know how to work on Subaru's. Thanks for the great advice.

 

gratefuldude: Yeah, the fans are on full blast. At least they sound like they are coming on normally.

 

I appreciate your responses and your time. Thanks very much!

Water pump is driven by the timing belt, so no adverse reaction or affiliation with the AC compressor running.

However, When the AC is on the condenser gets hot, thus causing the radiator to cool with hot air, which decreases the ability of the radiator to cool the engine. A partially clogged radiator may not be able to meet the demand of having the AC running for a long period of time.

Water pump is driven by the timing belt, so no adverse reaction or affiliation with the AC compressor running.

However, When the AC is on the condenser gets hot, thus causing the radiator to cool with hot air, which decreases the ability of the radiator to cool the engine. A partially clogged radiator may not be able to meet the demand of having the AC running for a long period of time.

 

 

oooo, good thought.

 

flushing the radiator out may do the trick

 

i had a similar problem on a trip from rochester to ithaca ny. got to my hotel, flushed the radiator in the bath tub, and my problem went away.

^ wow that's pretty ballsy haha

Replace the radiator cap just because. I am going to guess a clogged radiator. I wouldnt rule out a HG, have the dealer check it. Having hot air in the heater is a good sign, when HG go you dont have that as the coolant is getting vomited all over the road.

 

How about an air bubble in the engine.