head gasket replacement and valve job.

 

Our 92 Legacy was overheating really badly. We changed stats several times, bled the air out, etc. Went to the dealer where they told us the hydrocarbon rate was 800ppm.

 

We sent the heads out to do a valve job on them while we were changing out the head gaskets. Upon completion this morning I ran a compression test before starting the engine, and these are the rates I got. Tried the 90 twice. Squirted oil in the 90 and no change. So far no overheating, but have hardly driven it anywhere.

 

What are the possibilities here? Gasket didn't seal? Bad valve job on that head? Crack in engine? Seams like the compression would have jumped up if it was bad rings on that cyl. Is this even a problem? The engine runs ok.

 

Thx

How long did you run the engine before you took your compression test ?

If you assembled it and did a compression test , one of the hydralic valve lash adjusters may be holding the valve open .

Run the engine for about 10-15 minutes @ 2000 rpm ( make sure you rad fans are working )

Let it sit for a couple of hours (too cool off) and recheck your compression reading

If they are still low in that cylinder a leak down test would be the next thing to do .

 

hope that helps

SEA#3

Yeah! What "sea" said. Good advice.

Thanks Sea (#3). Yeah I guess I violated all the rules of a compression test. I did the test stone cold before the engine was started for the first time. I figured the test would be a good opportunity to get oil throughout the system and do something productive at the same time.

 

I'll check it again at operating temp. While I've got you and speaking of hydraulic valve lash, one side of the engine has got some pretty loud tappet noise. I'm not 100% positive, but it sounds like valve type action. I was going to pull the valve cover and rocker assembly and bleed the "lifters". I didn't run the engine at 2500rpm for 10 minutes, but we did drive it around the block about 4 times. Your thoughts?

 

BTW, a vacuum check (at operating temp) had the needle rock steady at about 18. This leads me to believe that the bad compression in that one cylinder may have "corrected itself" like you said.

Read this post

http://www.ultimatesubaru.org/forum/showthread.php?t=21878

 

SEA#3

becuse the cam would not be able to lift the valve as high.