Author Topic: 1998 Subaru Legacy Outback overheating  (Read 7235 times)

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1998 Subaru Legacy Outback overheating
« on: January 18, 2008, 01:53:01 AM »
A couple weeks ago my Outback began overheating. The rad fluid level had dropped severely, and the reservoir was way above the full mark. I replaced the thermostat and flushed the rad. After refilling the radiator (which was very slow, as there was a lot of trapped air, even with the bleed screw open) I performed some driving tests. The reservoir level was rising, and the rad fluid level was dropping, leading me to believe air is getting sucked into the cooling system. After driving it a dozen or so kilometers I had to put a liters or so of anti-freeze back into the rad in the middle of a drive (as it started to run hotter than normal). When I parked it back in my garage I couldn't find any evidence of anti-freeze leaking (at least nothing was dripping onto the floor). I'm thinking the head gaskets are probably the cause, as they are a common problem with this engine, but is there anything else I should check before I go through the painfully long task of pulling the head gaskets? I did a compression test, but my results were random (I think there's a problem with my gauge), and a leakage test didn't find anything conclusive (at least I didn't get any air bubbles coming out of the rad). I also checked the oil and it's clean as far as I can tell, though I don't have an expert eye. I would have figured that in order for air to get into the system, it would have to be pulled in from the suction force of the combustion chamber (which would also be the first place the gasket would go due to stress). Anyone have a suggestion on how I should proceed?

Linkback: http://www.trustmymechanic.com/forum/b1/1998-subaru-legacy-outback-overheating/16473/

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Re: 1998 Subaru Legacy Outback overheating
« Reply #1 on: January 18, 2008, 10:52:43 AM »
I would suspect a leaky radiator cap as it would break the siphoning effect from the reservoir to the radiator.

Then check the passenger floorboard to see if the heater core is leaking or not. A leaky head gasket you should notice a drop in engine performance. Plus like you checked, most of the time the coolant goes to the oil pan. You could hold your hand at the exhaust to see if it is getting wet (warm engine).

I would want a reliable compression check b4 I took the head off. AutoZone will lend you a good compression tester with a small cash deposit or CC#.

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Re: 1998 Subaru Legacy Outback overheating
« Reply #2 on: January 26, 2008, 07:05:34 PM »
Update:
I tried switching rad caps, but the problem persisted. I then placed the overflow hose into a can of anti-freeze to look for air escaping. As the car was warming up, I wasn't getting anything. Reving up the engine was causing intermittent bubbles. Once the rad fans came on the bubbles were fairly constant at idle.

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discretesignals

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Re: 1998 Subaru Legacy Outback overheating
« Reply #3 on: January 26, 2008, 09:04:06 PM »
You could do a block test to check for combustion gases in the coolant system.  The price on the tool is reasonable and it is fairly easy to use.

Here is an example of one on Amazon.com:

http://www.amazon.com/Combustion-Leak-Test-Kit/dp/B000I17Z68

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Re: 1998 Subaru Legacy Outback overheating
« Reply #4 on: February 10, 2008, 10:38:13 PM »
I ended up taking the heads off, based on a friend's recommendations. He took a look at the gaskets and saw what he though could have caused a small leak in them. I've got everything put back together, but have run into a new problem which I've posted about in a new thread - http://www.trustmymechanic.com/forum/viewtopic.php?f=1&t=16673

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Re: 1998 Subaru Legacy Outback overheating
« Reply #5 on: February 11, 2008, 07:36:17 AM »
Well?? I just spent the time answering your other posts. I hit enter and it said, "this post does not exist".

One of the mods must of thought it was a duplicate post and deleted it. But I didn't see anyone else online but guests.

Lost in hyberspace somewhere.

Just add to this posts and we'll still answer it.

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Re: 1998 Subaru Legacy Outback overheating
« Reply #6 on: February 11, 2008, 10:55:14 AM »
Ok, here's the new problem -

I've put it all back together, but it's idling really rough. It doesn't seem to complain if I rev the engine. I drove it up and down my driveway once, and it accelerated just fine. Any common causes for this? I don't know what's causing it, and the car ran just fine before replacing the head gaskets (other than the problem described in the above linked post).

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Re: 1998 Subaru Legacy Outback overheating
« Reply #7 on: February 11, 2008, 12:40:10 PM »
I would suspect a vacuum leak, maybe even the intake gasket? Confused Seems logical something happened during the repair.

You might want to check the IAC (Idle Air Control)valve. It has two vaccum lines on it.

Maybe a spark plug wire got stretched?

Connections on the EGR, MAP sensor, pvc valve?? All will produce a rough idle.

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Re: 1998 Subaru Legacy Outback overheating
« Reply #8 on: February 28, 2008, 11:11:17 PM »
I ended up taking the timing belt cover off and checking to see if it was still on properly, and one of the cam sprockets had slipped. I set it back on properly, but when I tried to start the car again, it would turn over, but that's it. I phoned a friend and asked for some advice, and he told me to check the valve clearance. Checking that, I found they were off quite a bit (due to an error on my part putting it back together), so I readjusted them and tried again, but still nothing. I've checked the engine thoroughly, spoke with 2 Subaru dealerships, but they had no good answer for me. I'm going to see if I can get my hands on an ODBII connector and see what the computer tells me (in case I accidentally damaged a cam sensor or something).

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Re: 1998 Subaru Legacy Outback overheating
« Reply #9 on: April 27, 2008, 05:22:50 PM »
I managed to get my compression tester working, and tested all 4 cylinders. I found 3 ran at 170 PSI, one was at 100 PSI. I pulled the head again, cleaned the valves, and looked for anything bent (everything was ok). I put it back together again (checked valve clearance again too). Tried starting it again, and got nothing. Then I took a vacuum hose off the throttle body (not sure what that hose is for) and squirted some gas into it. It ran, but oil spilled everywhere (I put the head gasket on backwards, silly me). Got a new gasket, put it back together again. Then I check the fuel line going into the engine: Turned the key on, and sure enough fuel came out. Put it back on, tried it again (even though I hadnít done anything) and it ran! Idled just fine.

So, thinking I had magically fixed it, I put the cooling system back on (this was yesterday). Went to turn it on today, and nothing! Same problem again. Whatís going on? All I did was put the cooling system back on, and a few wires that attach to the air intake sensors and the windshield washers.

Also, what that hose that goes straight down in the throttle control body? My service manual just says itís an air hose.

Edit:  I mean the air hose attached to the intake manifold, not the throttle body.

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