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Overheating Forester


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21 replies to this topic

#1 nberrong

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Posted 25 November 2003 - 09:24 AM

Hello:

I have a 98 Forester L, manual, with 132K miles that has overheated twice, and no one can figure out what the problem is. I thought I would see if anyone here had any ideas.

The first time it overheated, I was travelling on the interstate running about 75. I happened to look down and noticed the temperature gauge moving down. As this gauge has never moved before once the car has reached operating speeds, I kept watching it. It returned to its normal position, but soon thereafter rose quickly up to hot. I immediately pulled over and shut off the car. There was no steam. Once the car had cooled off, coolant was added and the car was fine the rest of the trip (about 20-30 miles). The next morning, it was pressure tested by a general service station, who found no indications of any leaks.

That night the car was driven about 40 miles with no problems - the temperature gauge was at normal position the entire trip. The next morning the coolant level was low again in the radiator. Level was okay in the overflow, but there was an oily-type substance in the overflow. So I took it to a nearby Subaru dealer to be checked out. All they found was a bad radiator cap, which was replaced. The mechanic thought that the oily-looking substance was likely old antifreeze.

The car was driven by my father during the next five days - he put about 500 miles on it. No overheating problems. On the 100-mile drive to return it to me, it overheated again, going from normal to pegged in only a few seconds. Notable I am sure is that it overheated in much the same location as it did before - on the downside of a high-elevation area. It was towed to my usual mechanic, who has not been able to find anything wrong.

I have been suspecting head gasket troubles, but my mechanic tested for exhaust gases yesterday and found none.

One other thing I will mention: it overheated on my first drive beyond just to/from work after having a new clutch and rear main seal installed. I don't think it's related, but at this point I don't know what to think.

Thanks,
N.

#2 Subie Gal

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Posted 25 November 2003 - 02:41 PM

classic symptoms of head gasket failure

is your mechanic a subaru tech?

did they do a hydracarbon test?

Jamie

#3 cookie

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Posted 25 November 2003 - 03:39 PM

this is a classic head gasket failure.
This can be very hard to find as the gasket closes up as it cools.

#4 Phillip

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Posted 25 November 2003 - 03:46 PM

Before I pulled the heads, I'd replace the thermostat. A sticky stat can cause intermittent heating problems.

#5 cookie

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Posted 25 November 2003 - 03:49 PM

You can try a thermostat, and a cooler one might work for a while for short trips.
In the end the heads have to come off.

#6 theotherskip

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Posted 25 November 2003 - 05:44 PM

which motor, 2.2 or 2.5? if it is a 2.5, it definately sounds like a head gasket. a thermostat will usually only have trouble either opening or closing, not while you have been running for a while, but it can't hurt to try a $15 part first.

another thing you can try is to run it on the highway for a good 30 minutes, then take the cap off the expansion tank (not the radiator!). if you see bubbles, that is a pretty strong indication you have a blown head gasket. when mine went, it was a small leak that would only open up after extended driving. i caught it early and changed it before the overheating could warp the heads.

i wrote a site with a lot of info about the head gasket problem. you can view it here .

#7 99obw

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Posted 25 November 2003 - 05:51 PM

Make sure that the radiator is properly bled of air when adding coolant. A little bit of air can cause it to overheat.

I found my headgasket failure by warming the car up until the fans came on, then driving it around hard, 5k shifts, etc., then immediately raise the hood and look in the coolant overflow bottle. Rev the engine to 2-3k, do you see bubbles? Mine looked like boiling water from all of the bubbles.

Before I knew what the problem was for sure I replaced the thermostat and radiator cap. It didn't actually help anything but it is a cheap place to start.

Good luck.

#8 nberrong

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Posted 25 November 2003 - 10:43 PM

Yes, it is a 2.5.

My mechanic, at my request, ran a hydracarbon test, and it came back clear. If that test is clear, does that rule out a head gasket problem? (My local mechanic does not believe it to be a head gasket, but is at a loss as to what it is. The mechanic at a Subaru dealer who looked at it last week believed it to be a bad radiator cap. He also did not think it was a head gasket, and saw the liquids siphoned out of the overflow.)

I am at a loss on how to proceed. I have really liked my Forester, and was planning to drive it many miles past its current 132K. However, I travel a lot and need a reliable car - I don't want to worry every time I venture out of town about whether or not I'm going to end up sitting on the side of the road. Fixing the head gaskets is cheaper than a new car, but the last thing I want to do is replace them, only to find out that wasn't the problem. Ugh!

N.

#9 alias20035

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Posted 25 November 2003 - 10:49 PM

When an EJ25 head gasket goes, it usually goes big time and is quite easy to detect via a pressure test and/or hydrocarbon test. So it looks like you have good head gaskets.

I would hedge my bets on the radiator pressure cap.

The radiator cap keeps the coolant pressure at 11-15 PSI to raise the coolant boiling point. If it fails the coolant under pressure escapes to the overflow and usually overflows from the overflow. When you lower the pressure of the coolant it can boil and its cooling capability is significantly compromised. The boiling temperature rating of coolant is usually rated at 13 PSI.

They do wear out and are generally changed along with the thermostat.

The symptoms you describe are exactely like what happened to my 93 Legacy EJ22. I swapped both the thermostat and rad pressure cap, no further problems for 200,000+ km. I don't know which one was bad, but thermostats usually stick in an open or closed state.

When they pressure test the cooling system they remove the rad cap to install the test gear, so it is the only thing not tested (other than thermostat).

#10 CROSSTBOLT

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Posted 26 November 2003 - 04:40 AM

No matter what, it is cheaper to fix the old ones than to buy new ones. Alias is right about the only thing not tested: the radiator cap(pressure). The Forester is a neat vehicle. Stick with it and use personal references if you are not gona do the work yourself.

#11 nberrong

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Posted 26 November 2003 - 09:36 AM

But, would a bad thermostat and/or radiator cap cause the car to lose coolant? I drove the car a fair amount last night, and this morning the overflow was empty and the level was down in the radiator. But, multiple pressure tests have failed to show any leaks. So the assumption has to be that it is burning up in the exhaust. Can it lose coolant through the exhaust and not be a head gasket?

The radiator cap is new, but I don't know if the new cap was tested or not. A bad radiator cap was all that a Subaru tech at a dealer found wrong with the car a week ago, prior to overheating episode #2.

Thanks for everyone's help and suggestions!

N.

#12 99obw

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Posted 26 November 2003 - 10:29 AM

The failed head gasket will allow exhaust gasses to force coolant out of the radiator and into the overflow, which will eventually overflow itself and cause a net loss of coolant. When the engine cools the coolant will be drawn back into the radiator from the overflow and both can be low.

If you have time try the procedure I described and let us know. It sure sounds to me like your coolant loss is due to exhaust gasses forcing the coolant out the overflow.

#13 nberrong

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Posted 26 November 2003 - 10:49 AM

99obw: I will try your suggestion and report the results, but not until Sunday. I am driving a different car through the holiday weekend.

One more question: Any chance the problem could be the water pump? The timing belt was replaced at about 105k, but not the water pump. (I didn't know it should be done and the dealer didn't say anything about the water pump.)

N

#14 99obw

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Posted 26 November 2003 - 10:54 AM

Doubtful. I suppose it could be leaking, but I think you would notice that. Usually the Subaru water pumps tend to fail by seizing, and you would know if that happened for sure.

#15 meep

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Posted 26 November 2003 - 10:57 AM

water pump leaking?

How old is the pump?

Damp spot under the front of the engine?

Mike

#16 cookie

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Posted 26 November 2003 - 11:25 AM

have a fitting to test the cap. testing the cap is part of a pressure test for a good mechanic.
I will be very surprised if this is not a head gasket.
The fact that the guage drops then rises sudenly is important.
When gas escapes into the coolent it takes it away from the sender for a moment. Thenthe coolent hits the sender as the gas escapes through the cap to the overflow tank. At that point it regesters the real temprature.
Right now this gasket is a tiny leak, but it will get worse!
If this was my car it would get..
1 New radiator unless it is excellent.
2 Head gaskets
3 New hoses
4 Thermostat
5 cap if not new
As long as it was down this far it would get any other service due like water pump, belts, etc.
The busses I serviced ran NY to SF and I treat my cars the same way.
I got 17 years out of my last Mercedes using standard commercial fleet practice for maintence, and since the payments were five years that was 12 years with no payments. At this rate you can do good maintence and still be way ahead.

#17 alias20035

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Posted 26 November 2003 - 02:53 PM

When my pressure cap went, I lost three out of six litres of coolant, and first noted a fluctuating temperature gauge (it went up, then down, then way up at which point I pulled over). Every mechanic I spoke to indicated that the head gasket was gone, but no pressure test (cooling system and cylinder) or hydrocarbon test could find it. I put in a new thermostat and pressure cap (and coolant) and the car was fine for many more years until I totalled it.

I would change the cap and monitor the car carefully for a few days (or weeks) and see what happens.

The EJ25 DOHC does not develop small head gasket leaks, it develops big ones!!! Or small ones that develop into big ones in short order.

Since his pressure test and hydrocarbon test is unrevealing you have to go on the assumption that the head gaskets are good until proven otherwise and look at items such as water pump, thermostat and pressure cap.

I indicated pressure cap because I had the EXACT same problem on on my Legacy, and my friends 97 Outback did the same thing but in his case he had the head gaskets changed and it turned out that they appeared to be good, the mechanic later determined the pressure cap was bad and as a result he was not charged for the head gaskets.

As for the item Cookie mentions:

1 New radiator unless it is excellent.
- Subaru radiators now last 10+ years, check to see if the fins have separated from the coolant tubes, most likely not.

2 Head gaskets
- pressure test and hydrocarbon test not revealing, so assume they are ok until proven otherwise

3 New hoses
- at 5 years of age you are due for new hoses as a precautionary step, but they are not cause of this problem

4 Thermostat
- could be bad, change it

5 cap if not new
- could be bad, chane it

I will add water pump, check it for leaks. In general the water pump will last between 1.5 and 2 timing belt cycles (60,000-120,000 miles). Often the pump is changed even if good during a timing belt change since it is relatively inexpensive.

#18 theotherskip

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Posted 26 November 2003 - 05:04 PM

Originally posted by alias20035
The EJ25 DOHC does not develop small head gasket leaks, it develops big ones!!! Or small ones that develop into big ones in short order.



i put over 1000 miles on my car between when it first overheated and when i replaced the head gaskets. the leak was still small when i replaced it. i just made sure that the coolant was topped off and i wasn't beating it.

with mine, it seemed that the leak would only open up after a 20-30 minute run at fairly high speed. local driving would not make bubbles come through the expansion tank. i did notice that it would not siphon coolant back into the block, because it wasn't generating a vaccum if it was parked hot. so anytime i took off the radiator cap (which i replaced when i did the t-stat before changing the head gaskets), the radiator would be low.

i'm with 99obw. i think it's the head gasket. be careful not to keep overheating it, or you will be needing more extensive head work...

#19 alias20035

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Posted 26 November 2003 - 07:52 PM

Originally posted by theotherskip
i put over 1000 miles on my car between when it first overheated and when i replaced the head gaskets. the leak was still small when i replaced it. i just made sure that the coolant was topped off and i wasn't beating it.

with mine, it seemed that the leak would only open up after a 20-30 minute run at fairly high speed. local driving would not make bubbles come through the expansion tank. i did notice that it would not siphon coolant back into the block, because it wasn't generating a vaccum if it was parked hot. so anytime i took off the radiator cap (which i replaced when i did the t-stat before changing the head gaskets), the radiator would be low.

i'm with 99obw. i think it's the head gasket. be careful not to keep overheating it, or you will be needing more extensive head work...



Even a small leak such as this will show on the hydrocarbon test. The hydrocarbons (unburnt fuel and exhaust) will stay in the coolant until the coolant system is flushed. The hydrocarbon test is often able to detect leaks that occured quite some time ago. It is the ideal test to locate small intermittant leaks.

#20 gravelRX

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Posted 26 November 2003 - 09:21 PM

EXACTLY, to a tee.

1998 2.5 RS coupe with 91,000 miles.

I ran it hard but was religious in maintenance and used synthetic oil from 15K.

The dealer tried to get me to replace the engine.

Even down to the film in the overflow.

Like yours, it only did it every once in a while, I could have sold it with the headgasket like that but car karma would have gotten me sooner or later.

1300.00 later and sold the car for payoff plus 2000.00 dollars.
( gave the new owner all the records and receipts too)
Karma indeed.

Jay

if you have any Q's, email me at jaykili(at)cox.net

#21 Commuter

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Posted 27 November 2003 - 07:25 PM

When my problem surfaced (full write up on the board here somewhere) on my 97 OB, the first thing I noticed was an oil residue in the coolant expansion bottle. (I thought it was oil but it's a product of combustion gases mixing with the anti-freeze.) My temp guage never moved actually. It was at it's normal position and I was watching it closely back then due to all the reports that were surfacing. The leak was small and might have been that way for several weeks. After highway driving for a while, the expansion bottle would be nearly full and there were little bubbles coming up thru it. I caught it early.

In my research at the time (mostly all the threads on i-club), it appeared quite common that the failure mode was these "small leaks". The leak would not appear unless the vehicle was run hard (eg - highway or towing). Pressure testing etc with an idling cool engine would reveal nothing. The car could be fine for weeks just running around town. I can't comment on the "sniffing". I'm not sure what to make of that coming up negative.

You also mention the overheating occurred on a down hill. I presume that you were driving "up" a hill just prior to that? This could trigger the overheat. And does anyone know... would the forward tilt of the engine cause coolant to move off the temperature sensor (that is, be hit with a pocket of combustion gases) and the temp to shoot up?

Sorry... but given the year, the mileage, the Phase I DOHC 2.5L, the symptoms, it all strongly suggests head gasket failure to me.

Commuter

#22 cookie

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Posted 28 November 2003 - 12:36 PM

the hydrocarbon test came up empty. I would have it redone by another garage.
My reccomendations are for what I would do now at 50 plus years of age, not much time, and not a lot of energy for mechanical stuff.
When I was broke kid I would have driven this car with no thermostat to keep it from heating up until I had the money for a head gasket set, and changed it over a holiday.
I only fixed what was immeadiately broken then.
As for the radiator the best thing to do would be to have it inspected by a trusted radiator shop at five years old. It should be ok if tanked and cleaned. If you are broke you clean it yourself.
Inspection of the raditor happens inside of it.
You have to look through after putting it in the cleaning tank and see how many tubes are thin or plugged.
My father in law in New Zealand drove a mini with a leaking head gasket for several years.
He filled the water each day, drove short distances, and never missed filling it.
I could not stand it and changed the gasket for him.




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