Head Gasket Failure-- ? not

[wrsub101]

First off, thanks to previous posters.  You helped me straighten out my son's 2000 outback.    It would start and would not run, and the problem was the swollen O-ring on the fuel pump.  I had to buy 5 of them, so to pass it forward, if anyone needs one free, just let me know on this forum.

 

Next (2 years later) came the overheating and brown stuff in the coolant.   The oil also looked like it had water in it.   This happened periodically although the car ran pretty good when it wasn't overheating.   None of the usual stuff worked, like changing fluid, replacing the thernostat.  A CO2 test on the coolant was positive, plus the coolant looked like it had burnt exhaust stuff in it, so I decided to replace the head gaskets.    BTW the compression was good, and seemed to hold OK.   But I wish I had done a pressure test on the cooling system to see if it held pressure.  More on that latter.   This all seemed typical of a head gasket failure.

 

Getting the heads out was tough (doing in the driveway and it got cold here), but its a SOHC so they came out.   The engine mount bolt on passenger side got mangled, so I had to get them out without raising the engine on that side.  

 

Much to my surprise,  the heads and gaskets didn't look too bad.  Even more surprising,  they were Six Star MLS gaskets, so someone had been there before.   Got the heads surfaced and pressure checked for cracks and they are OK.

 

Honestly, I'm not sure where the exhaust gas in the coolant came from....  Here's my plan:

 

Reassemble the whole thing being very careful to torque it down right.   Will use new head bolts because I now know these have been torqued down twice already, and don't want another failure.

 

Will inspect the oil pump and likely replace the water pump.

 

My question:   Any other way for exhaust gasses to get into the coolant?  I can't think of any

 

Thanks for any ideas.

 

[idosubaru]

Resurface the heads.

With two overheats i'd call around and see if you can find someone to resurface the block.

 

Replacing the head bolts is pointless and I'd consider it a bad thing because it's a false sense of security on an otherwise benign part. They are clean so you get clean threads and accurate torque, that requires cleaning the block hole threads as well and you can have the old bolts hot tanked at whatever shop resurfaces your heads. 

 

More than likely the engine was significantly overheated previously, the heads weren't resurfaced, or the block face wasn't very clean, or just a mistake was made along the way. 

The slightly offbeat symptoms (mixing, etc) are classic of headgaskets that have been previously replaced.  I was even thinking that as i was reading, before i got to the part about the new headgaskets already being installed. 

[DaveT]

It's very hard to tell they are bad by lookng at them. The tiny leaks that cause mild cross contamination are tiny. Don't show up with compression tests, coolant system pressure test, etc. Oh, sure when they are outright blown, you can usually see a damaged area. Theoretically, a tiny crack in a head or a block could cause similar cross contamination. From my experience, and what I've read, that would be rare.