Overheating Subaru Legacy AWD Wagon...

Probably what is happening is that there is air in the cooling system, resulting in intermittent blockages. you need to bleed the air out.

jeff

Ya mon, I tried that! When I initially filled the radiator I would make sure it was full, then open it and let the air out, and then close it, making sure the bottle was full. It was 'drinking' from the overflow bottle quite nicely before it started overheating. Even while overheating it was filling the bottle to the top, and then when you shut it off it would drop the level in the bottle about an inch.

Tried again today, making sure there wasn't any air (or trying to...)

So what's the state of the water pump and head gasket? Is there strong flow when you pinch the upper hose? Good flow looking into the rad? Blown head gasket can give you the same symptoms.

If you can get an exhaust sniffer, check for exhaust gas at the radiator neck. When you filled the coolant, you did have the heater set to full hot, right?

Good post. I think he did more things correctly than most. The ONLY other thing to consider would be filling/burping the system with the front of the car elevated OR by using some type of vacuum device on the cooling system. I have also read of someone filling the system through a disconnected hose? The best may be to fill (heater on max) with the front on ramps or up a curb/whatever, rad cap off, run till fans come on/t'stat opens, check the radiator and fill, fill o'flow bottle to a little over the full line, put rad cap on, allow car to cool (overnight if necessary) repeat. If you do not repeat, make sure the o'flow is topped up to the line, drive car and monitor heat and coolant levels. If you still have problems - headgasket is the only thing left. Phase I 2.5 engines are notorious for that problem. A swapped engine may not have been 'purged' and could easily have a HG problem. Sometimes, comparing sparkplugs will show one that looks different. That cylinder may have coolant in to it on occasion from the bad HG. Bubbles in the radiator of combustion gasses is another. That why an exhaust sniffer would also be diagnostic.

Carl

maybe pressure test the cooling system.

I would worry that pressure testing a 10 year old cooling system might create leaks in the radiator...

But of course I did!

Well, after I started adding coolant...

I'm afraid...

"I caught the head gasket leaking in my 97 subaru a few years ago, at 96k. It cost me $650, and they replaced front and rear main seals at the same time for just the cost of the seals, somewheres around $50-75 each if I remember correctly. I knew something was wrong- no power, really poor gas milage, the engine sounded louder than normal, I was constantly topping off the oil and the car smelled differently overall."

The engine runs really well, but after talking to a few mechanic friends and a Subaru service manager this begins to look like a BHG. One estimate is $600. The car has 336,000 miles on it, but runs well, everything works and minimal rust.

I said if it had a major problem I was going to get rid of it. I think I'll take it for Mass state inspection and have them look at it. I go somewhere anal, so they'll tell me if there's anything else. Hey, $29 for a complete inspection?!

It was up on ramps...BHG I'm afraid...

Engine has been replaced (don't know how many miles...) and radiator is new...all adding up to BHG...

I think johngdole has hit the nail on the...er...*HEAD*...

From another web site:

"Common symptoms: Overheating, often when slowing or stopped after extended high load driving. "

Sort of, although it's not random...

"The overheating can be seemingly random and sporadic."

Nah, it's pretty steady!

"Bubbles in coolant overflow reservoir, immediately after running."

Nope...steam in the radiator!

"Sludgy residue in coolant overflow tank."

Hmmmm...the original coolant didn't look good when I drained it out... it was kinda dark...I thought perhaps there was just gunk in the motor...

"Hydrocarbons in coolant overflow tank, this is tested by a mechanic with specialized equipment and is not evident visually."

Having this looked at Wednesday...

Is there any way I can check this myself?

Remember, Subaru boxer motor internals are right up there with Toyotas for being overbuilt to the point of bulletproof, and running practically forever - If the body and suspension are still good, might well be worth reworking the head gaskets and just keep driving it.

When it rusts into two pieces, /then/ you can junk it.

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If you have an electronic gas sniffer, you can stick the probe into the radiator neck or overflow tank.

Hi, Was it OK before you did the work? Or you worked on it for overheating problem>

Hi, Is the fan running when temp rises?

Way ahead of you, Ray! Brought it for MA state inspection (remember those?) He put the gas sniffer for the tailpipe in the filler neck and there were PLENTY of hydrocarbons coming out through the radiator!!!

I walked into this thing cold, being told it was overheating. After seeing all the new parts, I knew it wasn't going to be easy. BHG...

Everything works but the Head Gasket!!! ;)