Ok guys, take it easy on me on this one.

Background:
Just bought a 2001 XJ (6-00 build date) with 148,003 miles.
Running like crap, blowing more water out the tailpipe than 'normal' (from my experience)
Expectation was a new engine might be needed, was hoping for something less drastic.

Testing:
Didn't want to run the engine much, it was missing that badly and stalled twice during the test drive.
Starts quickly, but runs very badly, no power, very poor throttle response.
Found the coil pack was not bolted down (not good), but not a show stopper since the engine does run

1. Looked for and found low coolant, but since we just bought it didnt have a reference point so not sure of the obvious cracked head.

2. Got a pressure tester from autozone (thanks for the loaner program, Love it). No issues, holds pressure (16psi) for several minutes. Started the engine did see a small (1-2) psi increase in pressure over about a minute.
3. Compression Test (here's where the fun starts).
1 - 183
2 - 175
3 - 165
4 - 0 (nada, zilch, nunca)
5 - 170
6 - 165
The readings are a little high, not a calibrated pressure gauge, differential looks great except for the obvious. So looks like time to dig deep into the engine.
How do you get zero compression?
Took off the valve cover and didn't find anything broken. Obviously wrong, when cranking all rockers rocked and there was plenty of fresh oil in the upper valve train. Not too much sludge.
Tested #4 again, just to double check and again got zero.
(If I had a brain I would have done more testing at this point - a leak down or in this case blowing air thru the engine to see where it came out)
But being brainless I knew I'd see a HUGE issue if I opened up the head.

Removed the head, nothing worht noting. See pics. Head gasket looks good, valves look good, cylinders look good, lifters move up n down when the engine is hand cranked. See pics. May post a short video of the tailpipe water and engine running rough...

found what may be a crack in the head in the usual place, but not signs of water leaving thru it and back to the pressure test, no issues with holding coolant pressure.

There are signs of water being in #3 and #6 cylinders. The piston tops look too good, probably due to water injection and its wonderful cleaning properties.
A little buildup here and there at the top of cylinders, but not bad. Cylinder walls look great (excpet for #3 and #6 with water stains).
A tiny amount of scoring on one, but more visual than anything (can't feel it with a finger nail).

So the dilema, what to fix?
New head assembly (non 00-01 with issue) TUPY or other is $600.
Rebuilt engine > $1300+
Used engine - Cheaper but an unknown quantity.

I guess at this point its time to pull the short block and see what's up inside.
Then make the call?

 

Definitely should have done a leakdown test!!! Probably has ring lands blown out of the #4 piston

 

Agreed, but no going back now.
Didn't see anything wrong with the pushrods, but maybe one was holding a valve open (didn't check specifically for this either - I know, rookie mistake)

Even without any rings I should have gotten some compression.... even if only 10 PSI.
Should I be only looking at the cam/valves at this point?
Since the lifters move freely, is it possible one is stuck causing a valve to hold open?
Seems unlikely.

I'm still looking for a simple solution and would rather not have to go the full monty.

 

Well, the main cause of zero compression is a stuck valve but you said rolling it over that all the valves moved ok so that's probably not the problem.

 

1. Put head upside down (spark plugs installed) and fill each combustion chamber by ATF.
you will see, which valve is leaking.
2. Turn crank to move pistons down, fill each cylinder by 1/2" of ATF.
I am pretty sure you have bad valve/seat, if compression is 0, you'll see bad valve leak immediately.
If there is a crack, it is not big enough to have 0 compression.
Did you do wet compression test?

 

In response to gomuddin; I did see the valves were moving but didn't measure the travel or height. If one were not closing fully by 0.020" or so I wouldn't have noticed. Not sure how far open a valve would need to be to net zero compression, but I'm betting at starter cranking speed it doesn't take much.

On the ATF leak test; no light leaks in the head now so I wouldn't expect to be able to see a significant enough leak of ATF to be meaningful. I will test the cylinder/piston with ATF to see if it weeps past the rings.

Is there a way to check the pushrod height / travel that is generally accpeted as valid? It would be nice to diagnose the lifters/cam for #4. That will be much harder now that the head is off (should could woulda). I don't see how a lifter can be too tall, but I've been surprised before....

 

I would spend more time with the head. Maybe spend the 80 bucks and bring it to a machine shop and have them go through it?
Those valve seats look funny to me. I don't remember being able to see that noticeable of a ridge around them when I was lapping mine. I don't really remember, and I no longer have an extra head laying around to look at. Could have already had a bad head job done before?

 

I may send the head to get checked for cracks and flatness. I expect it is flat enough since there was no overheating and the gasket looked good.
Not crazy about putting the 331 casting back in, but if it aint broke...

All the valve seats look the same, even the 'good' ones have that counterbore area.
Its not part of the seat, so not sure it is of concern. If that changed the seated position of the valve, it could make it harder to fully seat (assuming the lifter can't accommodate the taller protrusion of the valve end at the rocker).

 

So how do you verify lifters are ok?

 

Still trying to diagnose the problem, dont want to put this engine back together and still have the same problem (might create another). Nor do I want to dump money into it if I don't need to.

Heres a pic of what looks like a bad lifter on #4 Intake (right lifter in photo). Will pull it after work and see what can be learned.

Also will try to inspect the cam for damage, is this possible without removing the cam?

Is a dial indicator on top of a pushrod a reasonable method to measure the cam lift height?

Help!

PS
Put ATF in the cylinder last night, no noticeable leakage in 30 mins.

 

Turn the crank, is piston 4 moving?

Any metal in oil?

 

0 positive psi is very significant. A crack or a burnt valve will still yield pressure... but not much.

Imagine this... your motor sucks and blows constantly (thinking with the head off.) And now your bottle neck into a small passage about the size of a pencil eraser... you will still get 15psi.

If your motor is never letting air in the intake you will get a huge negative number that will come up with a negative pressure.

By experience I've had both bad lifters and bad head gaskets to similar things.

Place the head back on the motor w/ lifter rods. Slowly crank the motor and verify all valvds opening and closing.

A bad head gasket will be super stiff and burnt around an air leak if it's bad enough to no create any pressure.



My guess would be a lifter collapsed. Typically a broken cam wouldn't cause just one piston to act funny.


Good luck

-Adam

 

Thanks for the ideas and details, the valves were cycling, could see the intake moving thru the spark plug hole.
Pulled the lifter tonight and found it jammed up- not frozen in the down position, but the top was cocked sideways lodged in the body. Don't know how far the lifter depresses under normal conditions, but this one wasn't moving at all. Having issues uploading the pic.
I smacked it with a socket and freed it up, took it apart. Had some sludge in it and a few small metal shavings/chips, the button the rod sets in has a score mark were it was wedged. Won't reuse it.
Thru the lifter hole could see the cam lobe, it looks good

So from here I think it's clean all the lifters, get the head checked for cracks, and repair any issues (don't want to put the 331 back in but if it ain't broke) then start re assembly.

 

Here is the stuck lifter pic.

Is this a normal thing? Seems odd to have it hold a valve open vs being stuck in a compressed state and not opening the valve fully and making lifter noise instead.

 

If you don't want to check valves by ATF (easy way), use lapping compound to check them.(hard way)