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2002 Forster
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8 Posts
Discussion Starter #1
Just had both HG's replaced on my '02 Forester this week (what a surprise) and also had a new Subaru thermostat put in. I had a visible coolant leak, but the temp gauge always remained normal, the coolant never overflowed and the engine never overheated.

My mechanic is very reliable, but immediately after the HG's were replaced the car is now having coolant overflow into the overflow bottle (and there are bubbles in the coolant in the overflow bottle) after a few miles of driving. The temp gauge goes up sometimes, but not always, when the coolant overflows. My mechanic thinks it is an air pocket in the system that he is having a lot of trouble getting out and still working on. Is there anything else it could be? Could there still be an HG problem even after both were replaced? Any other thoughts or ideas? Thanks!
 

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1998 Forester
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602 Posts
Just had both HG's replaced on my '02 Forester this week (what a surprise) and also had a new Subaru thermostat put in. I had a visible coolant leak, but the temp gauge always remained normal, the coolant never overflowed and the engine never overheated.

My mechanic is very reliable, but immediately after the HG's were replaced the car is now having coolant overflow into the overflow bottle (and there are bubbles in the coolant in the overflow bottle) after a few miles of driving. The temp gauge goes up sometimes, but not always, when the coolant overflows. My mechanic thinks it is an air pocket in the system that he is having a lot of trouble getting out and still working on. Is there anything else it could be? Could there still be an HG problem even after both were replaced? Any other thoughts or ideas? Thanks!
If the heads were warped and he simply replaced gaskets and didn't have the heads milled to spec...leakage will still occur. the Subie dealer that did mine said they send the heads out to be machined even if the measurements are within spec...they said in the past they would sometimes have that issue where after all the work to replace the gaskets...customer would be back pissed off.
 

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2002 Forster
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Discussion Starter #3
If the heads were warped and he simply replaced gaskets and didn't have the heads milled to spec...leakage will still occur. the Subie dealer that did mine said they send the heads out to be machined even if the measurements are within spec...they said in the past they would sometimes have that issue where after all the work to replace the gaskets...customer would be back pissed off.
My mechanic had the heads sent out to be milled - I guess the possibility exists that could they not have done it properly?
 

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1998 Forester
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602 Posts
My mechanic had the heads sent out to be milled - I guess the possibility exists that could they not have done it properly?
I would tend to doubt it...mechanics usually know which machine shop does a good job as their butt is on the line...so maybe it is an air pocket except that bubbles in the overflow is a bad sign. Maybe the heads were not torqued properly when re-assembled or something casued a gasket to shift slightly...hard to say...sounds like he might have to pop them off again to make sure.
 

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Just a note its possible to install the head gaskets the wrong way around on certain motors. A friend just replaced his himself and ended up putting them on upside down. Afterward it acted just like yours is. I'd say something wasn't done correctly during the install.

You could get a hydrocarbon test done on the coolant. It will tell you if the headgasket is leaking still.
 

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1998 Cayenne GTS 6speed
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1,752 Posts
Check if it's the thermostat or water pump. Otherwise - HG. And make sure timing is set correctly.
 

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98 Fozzie
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170 Posts
Take it back to the mechanic and tell him....

I bet its just air pockets and it needs to be bled more (takes a while with these motors).
 

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2002 Forster
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8 Posts
Discussion Starter #8
Definitely not just air in the cooling system...my mechanic is taking everything apart again today after a failed compression test.
 

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2002 Forster
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Discussion Starter #9
In case anyone wanted to know, here was the final verdict...turns out one of the new head gaskets was defective causing exhaust to leak into the cooling system. My mechanic had to redo the job completely - and to his credit I was not charged any extra and he rented me a car at his cost while he did the work. I've put 100 miles on the car so far and all is good so far.
 

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2001 Forester S
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106 Posts
What the mechanic is saying is that he did everything right but the new gasket blew immediately. Seems very odd. Could your mechanic have made a mistake in putting in the new gaskets or reassembling the engine, and is just saying it was something else (that you cannot verify) to safe face?
 

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2008 2008 2.5i-2018 XT
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13,212 Posts
Likely that either the mechanic missed something in examining the HG or screwed it up putting it in. Not hammering him. Mistakes happen. Great he took care of ti.
 

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2002 Forster
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Discussion Starter #13
I will be bringing in my Toyota later this week for an oil change and brakes and will try to remember to ask what brand of HGs he used.

As far as the HG being defective or my mechanic making a mistake, I believe it was a defective HG for the following reasons:
- I've been using the same shop for 15+ years and know them all well
- He correctly fixed the HGs on my '97 Outback (which I no longer own)
- When fixing the HGs on my '97 Outback he accidentally cracked a head by over-tightening the bolts, owned up to the mistake then and fixed it at his cost

I can only hope everyone else on this forum who can't fix, or doesn't have the time to fix, their cars themselves has a mechanic who is as good, fair priced and honest as mine. And, if anyone wants a recommendation for a great mechanic in lower Westchester County, NY just let me know.
 
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