Compression Test 0 psi

[Brendan]

My liberty overheated on the highway after getting it home and changing out crank/cam sensors after error codes and replacing the water pump/thermostat and PCM i think i have the over heating issue solved.

But now I am down to multiple misfires error P300.

I removed all the spark plugs and did a compression test with the following results
1: 155
2: 180
3: 170
4:150
5: 0
6: 170

(I assumed standing in front of the car facing the engine 1,3,5 are on my right side and 5 is farthest from me)

I tried adding 2 tablespoons of oil to number 5 and still got a 0 psi.

Any idea what the next best step would be or the first think to look at, I have googled things like rocker arm or lifts.
I put new spark plugs in before starting this project and notice that number 5 has come out black again and 1 / 3 are little black not as bad but still burnt. 2/4/6 seems not too bad.

I cant really see any coolant in the oil or white gunk in the oil.

 

[lfhoward]

Sounds like a valve must be stuck open on #5. Just a thought, you could hook compressed air up to that cylinder to see if the pressure comes out the intake or the exhaust pipe. That would narrow down which valve.

Hopefully it is something like a lash adjuster or valve spring. But overheating on this engine tends to make them drop valve seats. You will need to remove the valve cover to know what happened. Unless you have a borescope on hand to look at the bottom of the valves through the spark plug hole. Fingers crossed for you.

 

[Brendan]

What kind of psi should i blowing in the spark hole, i think i can rig up a something to blow into it my compressor is only 90 psi.

 

[lfhoward]

I should note I’ve never done this so you should take my advice with a grain of salt. But I saw Eric O. do it on his South Main Auto channel on YouTube. I would start small like maybe 20 lbs if it were me. Before pressurizing, take the intake hose off the throttle body so you can check for the sound of escaping air. Also listen at the exhaust pipe. If it doesn’t hold compression the air has to be going somewhere.

 

[Big Al]

I've never done a leak down test before either, remove your oil filler cap and listen for blow by there to, that would mean your head gasket, rings might be gone or you have a hole in the piston on #5.
Also, you may have to hold your throttle body butterfly in the open position to feel or hear any air heading that way.

 

[Brendan]

So I got my Valve cover off and not the 2nd last rocker was sitting on the bottom of valve pan, I cant push the lifter in by hand so I am guessing that is stuck and the rocker popped off.

I lost 3 bolts of the valve cover trying to pull it out and only found 2. I looked everywhere and can;t see them, I had the spark plugs covered of and doesn't look like its in the valve pan or near the timing chain. So i will pick up replacement bolt.

I have 4 x 10 mm bolts and 5 of those 10 mm ones with the threat that sticks up. Does it matter what bolt i replace it with ?

Does it matter where the bolts go on the cover since i have 4 out and don't remember where they came from ?