0% Compression on #5

[sailchef]

Question: Could 1 broken head stud cause the related cylinder to show 0% compression? Or, would it more than likely be something else, like a blown piston, or seized valve?

It’s not my car. I’m looking at it this week. It may turn out to be a purchase. I’m told the motor does run, but on 5 cylinders.

Should I attempt a leak down test, and, with out any compression what could it tell me.

[dad911]

If you do a leakdown, listen to where it leaks out, intake valve, exhaust, or crankcase. That will tell you where the problem is. Could be valve, hole in piston, worse?

If it is 0%, you are buying an unknown project, basically a roller. Price accordingly.

[Porsche_monkey]

I would guess at 'zero' a bent valve is the likely culprit. It's going to need a rebuild of some sort.

[john walker's workshop]

psi is compression, like 150 psi. % is leakdown like 4%. so you're getting 0 psi compression i assume. a broken stud wouldn't do that unless, because of the broken stud allowing hot exhaust to escape between the head and cylinder, the exhaust burned out a larger channel over time. that would make an obvious sound when running. a real tight adjustment screw that held the valve open would do it, as well as a hole burned in a piston, bent valve, burned valve, broken rocker.

[sailchef]

Thanks for the input. the present owner seems to think the broken stud is the cause of the problem. he mentioned a loud sound. I want to look at it understanding all (or most) of the possible causes. I have extra gaskets and lock nuts to remove his lower valve covers and was going to see if he'd allow me to inspect it.

So on the grusome side we could have a hole blown thru the piston, or a blown cylinder head.
and on the other side it could just be a adjusting screw thats too tight.

I should be going sometime this week to look at the car. Again, thanks for the input.

[berettafan]

well let's say it's a bent valve.

how did this happen....over-reved? if so what about rod bolts....on all 6?

[briancoates]

If the engine was running and suddenly lost compression then it will not be something simple like a valve out of adjustment! When I bought mine it ran as smooth as silk, but.... see photos!




repairs needed? piston, cylinder, conrod, crank................. I bought a new engine!

Good luck but be prepared for the worst and pay accordingly.