low compression in 1 cylinder after head gasket replacement

[tereed2 at gmail.com (T. Reed)]

Hey guys,

I changed the head gasket in my 16v during this past week. After getting 
it all put back together, I did a compression test.

All cylinders were ~180 psi except for #3 which was zero (!). Actually, #1 
was zero as well the first 4 times I checked it, then it shot up to 180 
psi on the fifth check. I have no idea why. At first I thought the 
compression tester was faulty since it's new and its from Harbor Freight, 
but #3 consistently measured very low, and #1, #2, and #4 were ~180 psi, 
as I moved the tester back and forth between cylinders.

I added some oil and #3 still came out as zero, but after I turned over 
the motor with the starter some more and tested again it went up to 35 
psi.

The head was resurfaced before being reinstalled. The shop said they took 
6/1000ths off. They also put one of my intake cam bearing caps on 
backwards.. I'm not very happy about that. I fixed it before re-installing 
the head.

What could be causing this low compression? As I see it, its either valves 
not closing, or stuck rings. New head gasket, new bolts.. shop said my 
valves leak "a tiny amount" but nothing to worry about.

The head gasket failure was between cylinder #3 and a coolant passage. It 
doesn't seem like a coincidence to me that this is the same cylinder 
giving me low compression. I searched around and found some people 
claiming a connection between a bad head gasket and stuck rings, due to 
coolant getting in to the cylinder. I don't know how to diagnose this, or 
how to solve it, though. Any tips would be appreciated.

I scraped the carbon buildup off the top of the pistons in order to 
ensure valve clearance after the resurfacing, but I didn't do this to 
the cylinder in question (#3) because it was already shiny clean.. 
probably from burning antifreeze.

The head was jet washed before resurfacing, but this didn't take 100% of 
the carbon off the underside of the cylinders.. there were a couple of 
black patches left over. I suppose its possible that there's a similar 
deposit between a valve and the head, and its leaking there.


Long story short, I decided to try starting it since if something is 
busted I'm sure I'll be unlucky enough to have to take it apart again 
anyway. I'm down on my car luck lately..

It started right away and sounds strong except for the fact that its only 
going on 3 cylinders. If I pull the plug wire for cylinder #3, there is no 
change in the sound.

Any ideas? This is my only vehicle. I've been bumming rides to and from 
work all week, and I'm really up a creek here if I can't get it driveable 
soon.

-Toby