2000 Outback EJ25 overheats when the air turned on

[RMVR53]

Hey all. Got a strange one. I've had the car for 4 years. Has 260,000 on it now. EVERY time you drive it, when you stop, there is the faint smell of hot antifreeze. I've replaced hoses, thermostat, and flushed the cooling system but its still there. It never overheats, just smells. Its never low on coolant. It overheats when you turn the air on. The aux fan is running when the air is on. It doesn't matter if your sitting still or driving at 50. After about 5 minutes you can just watch the gauge start climbing up till it hits the red and its blowing coolant into the reservoir. 

Ideas?

thanks

Bill 

 

Edited May 12, 2019 by RMVR53

[89Ru]

if you're smelling coolant there's likely a leak somewhere. Replace the radiator. I've had good luck with Spectra premium at RockAuto. Cheap insurance.  

[RMVR53]

89Ru - I'd agree but its been months since I topped the reservoir. To make sure it wasn't a failed cap or something, I topped up the radiator directly. It took less than half a quart for it to be running on the ground. About 6 months ago, I did find a leak in one of the small hoses on the back of the case to the intake. It would leak from a pin-hole right after you shut it off for about 6-10 seconds. It was such a small leak that it would evaporate as it hit the case. So I changed that and its cousin on the left side. 

I did have someone tell me today that if I didn't use a factory thermostat then that could be my problem. My replacement about a year ago was a Stant which I thought were OEM units. I'm stopping by a Subie dealer tomorrow and checking on that angle.

Bill

[idosubaru]

OEM is much different and more robust than standard stant.  

Can you Pressure test it?

If you do replace put the old one in boiling water and see what it does.  

Smell suggests some external leak.

While it’s apart flow test the radiator, it should flow all of a standard garden hose.  

[el_freddo]

My hunch is head gasket leak. 

Using the AC loads the engine enough that  the cooling system can no longer “look after” the blown head gasket and thus over heats  

If this is the issue, it’ll only get worse over time  

Cheers 

Bennie

[1 Lucky Texan]

clean-out between the a/c condenser and the radiator. On some older cars, debris/dead bugs can build-up in there.

[Gelbin Mekkatorque]

Did you burp the radiator every time after you messed with it?

Subaru radiators need to be burped otherwise you get air pockets down right at the thermostat and causes the vehicle to overheat.

To burp the radiator you need a wide funnel that fits in the radiator top TIGHTLY. 

Fill the radiator to capacity and then put another few inches in that funnel while holding it tightly in place.

Then reach down and squeeze the bottom radiator hose leading to the thermostat. If you are unable to do this by yourself then get help.

Once you squeeze that bottom hose (where the air collects) you'll get air bubbles up through the top of the radiator and funnel you've been holding in place. Once the air is gone it will suck the fluid from the funnel down into the radiator.

Badda boom badda bing your Subaru has been burped.

As long as your thermostat and fans are working properly you should be able to drive the car with the A.C on without further problems.

[RMVR53]

update - 

thermostat. Changed it out to a factory spec unit (aka dealer) and problems went away. Amazing the difference in size from factory to "replacement" you get from a parts store. I'd be ashamed to call that a replacement part. 

[heartless]

thanks for coming back and updating!

Glad it was an easy fix for you.

[RMVR53]

Dealer stat is on the right. OTC "replacement" is on the left

[Rooster2]

When motor begins to over heat, open hood, keep the engine running. Check the radiator over flow container for bubbles coming up from the liquid. If you see bubbles, that is a strong indicator of a bad head gasket. I hope you see no bubbles.