Background:
90-95 psi on all cylinders on a compression test. Did a leakdown but could not get any consistent nor believable readings. (<-First time doing one.) I did hear air through the oil fill cap so I thought it would be worn rings.

Now..... I finally got a chance to get the cylinder head off thanks to a couple stripped bolts. The cylinder bores look fine, no gouges or deep scratches. Nothing catches a nail. If the rings are worn, wouldn't the bores tell the damage?
Also, looks like t he headgasket is bad, but I don't have any mixing.

So, you think the valves might be the culprit?
Thanks!

 

Here are some pics of the head....

 

What were the leak-down test results? Acceptable readings are from 0.00% (not very common) up to about 12.00%. Above that there are problems, although the engine will run.

Unfortunately, though you couldn't get any usable results, now the head is off you can't get any to use for diagnosis. Unusual to have every cylinder read the same (low). Did you check the gauge?

From the pictures it looks like at least cylinders 3 and 4 were leaking at the head gasket, but with no real data to go on, it's guess work what (if any) problem there was.

 

When i was doing the leak down, I was getting crazy numbers like 65% loss on cylinder one and then 95% loss on the next. I wouldn't get a quick reading either, The gauge would slowly rise to a fixed point. I tried with the cylinder TDC as the directions said as well as BDC as Rennlist said.
I tried it over and over with consistent but off the wall readings, so I assumed I was doing it correctly. So, I decided it had to be at least the rings and decided to remove the head. I was prepared to see some serious damage on the block but it looked OK, so maybe the gauge is bad?

 

No, 65% is a reading I have seen plenty of times ( and 95% too). When you get readings like that you will hear the air pressure escaping somewhere, either through the exahust or intake (valves) or the oil fill cap (rings) or bubbling in the coolant tank (head gasket). Did you hear or see anything when testing? It can also corrospond to the compression readings: high leakdown but reasonably good compression can be rings or low compression and high leakdown can be valves.

 

Hey Clint, something that has happened to me many times is once you apply pressure to the cyl, it will turn the crank, and open a valve, causeing your numbers to change.

Mark

 

Only if you don't have the piston exactly on TDC (or "OT")

 

Dude...

There is so much **** on those valves, they are not closing completely.
You are lucky to get 95psi.

 

Even exactly at TDC, with all the plugs out, it takes quite a bit of effort to hold the crank still.

Mark

 

You don't need to hold the crank, set it at TDC, firing on whichever cylinder you are testing, and do the leakdown.

If you want to, and so far I've never needed it, use the flywheel lock tool.

 

I didn't hear anything through the exhaust. I did hear hissing at the oil fill cap, but did not feel air. I also heard air through the intake.

I'm still learning about alot of this but...
If the rings were bad, wouldn't there be some scratches on the bore?

 

That's 225K miles of fun! LOL

So, you think my problem lies in the valves...maybe have it cleaned up and I'll be ready to go?

 

Sometimes, but not always, rings can break and pistons crack, but no bore marks.
Goodson makes a tool to do cylinder leakdown with the head off. Or you could make one.

Some air leaking into the crankcase is ok, but without any real readings it's a guess.
Doesn't really matter how dirty the outside of the valve is, you are looking for it's sealing ability.
Take the head to a machine shop and they can test the valve seating for leaks.
It's going to need machine work anyway looking at the state of it.

 

Ok, last car i did a leak down on was a 996 GT3, factory procedure said to hold the crank from moving with a breaker bar. That was after bringing up the piston to TDC compression. That would take forever to have to reset the flywheel lock to test the cyls.

Mark

 

a leak down is a lot more reliable is you remove (or at least loosen) the exhaust and intake manifolds. then turn the crank so that the valves are all closed on the cylinder you are currently testing. then use a piece of flexible tubing (put one end in your ear, and the other in the exhaust and intake openings) and listen for leaks.

you should not hear anything at all leaking past the valves.