Am I overlooking something? Low compression

s1ngletracker · 01-06-2011

So this is a bit of weird story... here goes. This is all on my 93 Talon TSi AWD.

My water pump failed, the pulley fell right off it and it pissed all my coolant out, a block away from my house. Got into my driveway just as it was starting to overheat. Then started it up, drove it into the garage, and replace the water pump and reset the timing belt.

After this was done, car wouldn't start. Checked compression and it was low, 120-120-120-30 ish. Forgot to put oil in the cylinders and check again (stupid me, in a rush) so I assumed that I had bent the valves doing the timing belt job, moving the crank around without the timing belt on, and not having the engine at cyl 1 TDC.

I did notice valve marks on my pistons, but the cylinder walls looked fine. Got a rebuilt head and threw that on. Was very careful about not ramming the pistons into the valves, everything went smoothly. Fired it up tonight. It ran, but not well. Checked compression, same as it was before, 120-120-120-30. Now I'm really stumped. Did a wet test, cylinder 1 jumped up to 210! (added a little more oil than I wanted to) Cylinder 2 jumped up to 180. Skipped 3, checked cylinder 4. Went from 30-60.

First off, how the heck did my bottom end go bad? IS my bottom end bad? I had just done a compression test a few weeks before the water pump mishap, and all the cylinders were fine, around 175-180 I believe.

Is there something else i'm forgetting that could be causing this? I'm at a complete loss, some crazy weird stuff is happening, and I can't wrap my head around it.

Thanks for reading. I just need some input before I start pulling the motor.

Side question: How easily will a 4G64 bolt up to my head (the rebuilt one is a 6 bolt), accessories ( I want to keep A/C and P/S)? Thinking about throwing one in.

311evo · 01-06-2011

Do a leak down test maybe? you could then hear where the issue is.

**Goat Blower** · 01-06-2011

Well the fact that you have one really low cylinder kinda rules out stuff like the timing belt being off a hair, but I'm at a loss to explain how your rings could go that badly from the water pump. I'd do a leak down test as well, but the wet test pretty much points straight to the rings leaking like a sieve.

s1ngletracker · 01-06-2011

leakdown test results pending.

s1ngletracker · 01-12-2011

so i did a leakdown test with the engine in the car, but I did it more thoroughly on an engine stand after I pulled it.

Here is a picture that most easily details my results:

The thing that disturbs me is the intake noise in 3 & 4... this is a rebuilt head. The engine is obviously stone cold and outside the car, but should I be concerned about that? I tried rotating the engine back and forth to make sure the valves were closed fully, no real change in the noise.

1 & 2 seem expected, little to no noise in the intake and exhaust, i think the noise and compression loss is due to the rings.

I think either way this head is going to headwerks for a thorough inspection before I dare put it in the car. I might have them look at my original un-rebuilt head as well. They didn't do the rebuild.

I'd like to hear opinions on this. Is there anything I should test with the head still on the motor? I might wait a bit in case there is something else valuable to test.

Thanks for the help and sorry about the book!

Pushit2.0 · 01-13-2011

It sounds like standard issue leaking valve seats, It may be from crap on the intake valve seats, I would re-check your timing marks.

~John

s1ngletracker · 01-13-2011

that sucks, being that this is a rebuilt head! I was hoping the test results would just show bad rings like i suspected.

with the head off the block, can i rotate the cams and look at the valves when they open to see if there is gunk on the seats? This is a new head that was only on the car idling poorly for a few minutes, if i ran it more would they start to seat up better?

edit, just did it again with the intake manifold off so i could have a better listen to the intake ports. I could actually see bubbles of (some fluid?) around the valves that were leaking. really cylinder #4 is the worst, very loud. Cyl 3 is not as bad as I thought. Now i'm really curious and want to have this head tested/inspected by a machine shop.

s1ngletracker · 01-13-2011

fyi, head got sent back to the rebuilders for repair, after trying a few things he suggested. He thought something might be jammed in the valve keeping it from closing, gasket material or something. Rather than put it in the car to have the problem persist, I took the safe route and sent it back. I can live without yet another head swap this month.