91 Legacy with over heating problems

[helpermonkey]

Hello all.

I have a 91 Legacy L. 2.2 non turbo, automatic with 100008 miles on it.

Long story short My Crankshaft pully / Harmonic Balancer went bad and vibrated itself off. I decided to replace the timing belt and the water pump at the same time. Once I got everything back together I noticed that the car over heated after driving it for 10 minutes. I ended up replacing the thermostat and burped the system twice. The car did not over heat until I took it on a test drive and it over heated again after 10 minutes again. the heater is not working either which i assume means heater core is not getting any coolant. The car never overheated before I did the water pump and belt.

After all of the research I have done I can only assume there is some air trapped someplace in the lines that is not burping out or a bad head gasket. Since I never had the problems before I highly doubt it is the head gasket.

Is there a way to properly burp the system that I do not know of? I am at a complete loss on this. I never had this many problems with such a simple repair before.

[mike-tracy]

What is your plastic overflow bottle doing during all this? Does it overfill? When the engine is cooling down, does the system pull coolant back from the bottle? Also, most importantly, you must use a Subaru thermostat. 95% of the aftermarket ones are a poor design and have killed countless subaru engines by not functioning properly.

What I do to clear air pockets, is to fill the coolant into the upper radiator hose.
Once it's full, I resecure the hose and open both the radiator cap and the small bleeder hole cap (on the opposite side of the radiator) and fill the radiator till coolant comes out of the bleeder hole.
I put the two caps back one and let the car idle with the heat on full blast, and wait for the thermostat to open.
Pushing down on the radiator cap and rotating part way, any trapped air will blow into the overflow bottle.
Once this pressure is released, then I can open the cap the rest of the way and top off as needed, opening up the bleeder again if needed.

I recommend using gloves and glasses for this operation. I'm sure others have their own tricks, but this way hasn't failed me yet.

[helpermonkey]

The over flow was fine when the car Idles. It was well past full when I was driving the car and it was over heating.

I opened the bleed valve on the passenger side of the radiator. I poured the coolant in at the coolant radiator cap and closed the bleed valve when coolant reached the top of the bleed valve. I then ran the car with the cap off but with a funnel stuck in the cap. (I put duct tape around the outside of the funnel to create a makeshift gasket between the radiator and the funnel. I did not attach tape to the radiator just around the outside of the funnel.) The coolant level would then rise and fell. It would bubble over when I revved the car. I ran the heat on full every time I tried this.

I will try filling up the the upper rad hose first like you have done and see what happens.

[mike-tracy]

Yeah let us know what happens. I can't over emphasize how important a factory thermostat is in these older cars.

[helpermonkey]

Update time

I drained the coolant again.

I removed the t-stat. I did not replace the t-stat. I left it out. (The T-stat is an aftermarket one. It looks vastly different from the one originally in the car. I do not know if the original is a Genuine Subaru part. I did test the original in boiling water. It opened and closed like it should.)

I pulled off the upper rad. hos, filled it and reattached when the coolant was full in the tube.

I then filled the radiator at the radiator cap. When the coolant reached the bleeder I capped that and finished filling the radiator.

I stuck the funnel in the radiator cap hole, turned the heater on full blast and started the car.

I burped the system, turned off the car and recapped the radiator.

I restarted the car and took it on a test drive for about 1/2 hour.

It DID NOT over heat with the removed t-stat even when I drove the car up the mountain. (Yes I live on a mountain.) I did not drive it on the expressway but I did get the car to 45 mph. I would also like to note that my heater is working again and I have hot air when I turn on the heater.

I am gonna let the car sit for a few hours, take it back down the mountain and take it on the expressway for a few miles.

I have to conclude that the t-stat was not opening up. I conclude there 2 reasons for this after all my research. Either both t-stats are not working properly or I have air in the heater core.

[mike-tracy]

I think it was both the t-stat not opening up and the air in the heater core. Glad you're making progress. In addition to the factory t-stat being almost double in size, they also have the bleeder hole, and the lack of which I feel is part of the problem with most parts store t-stats.

[Legacy777]

This is what the factory thermostat looks like.

http://main.experiencetherave.com/subar ... P_4799.JPG

[93wagonship]

When I change the coolant I usually take the radiator out to clean and I use the top radiator hose to put clean tap water from a low pressure hose until it washes "everything" inside and come clean at the bottom hose. Then move the car around a little bit in my garage ramp to help remove all the tap water trapped inside before putting new coolant (it's ok to start the car without the radiator for one minute or so). This is the best way to reduce the accumulated sediment for me.

About the t-stat I've used an aftermarket one (stant XLStat) and it's been great. It looks almost like the OEM and have the safety hole as well. Don't run without t-stat cause the engine will run cooler increasing fuel consumption and engine wear.

To burp the system, a SpillFree funnel does the job well (let it cycle untill the fans come on twice). A new radiator cap is always welcome too.

cheers