checked my compression, bad news.

[Beached Bones]

HI, I'll write this long to try to give as much details as possible. I am a fair backyard mechanic but have never gone deep into the engine before.

My 92 XJ 4.0 auto (engine rebuilt 40,000 km ago by a mechanic), slowly and progressively started running real rough, lacking power, and would stall when coming to a stop. It has had poor mileage (9-12 mpg) It would surge at highway speed and the idle was inconsistant. Also my valvetrain noise is strongly noticeable and has been getting worse. Not long ago I changed my 02 sensor. Following some information posted here, I changed my Cap, Rotor, plugs and wires, no change, my Crankshaft sensor was replaced next and it was much better, my idle speed is right on, and I don't stall anymore. It still runs very rough, and "seems" to have excess water coming out of the exhaust (no catalytic converter) I don't think I smell coolant in the exhaust but am not 100% on that. Also I don't think I am loosing coolant, if so very slowly, with no visible external leaks. There is no oil in the coolant/antifreeze, and there is no coolant in the engine oil (no milkshake like or brown oil). I have checked that there is spark with a inductive spark tester. Fuel also seems fine but I havn't really tested the presure or anything.

After all that I was guessing that maybe my headgasket might be blown between a cylinder and the water jacket, or that I've got some problems with my valvetrain. I don't think the piston rings are the problem as they were replaced with the engine rebuild. So I went today a bought a pressure tester. the readings I got were as follows:

#1 130
#2 145
#3 140
#4 0 both dry and wet test
#5 140
#6 0 - 60, initially went up to 60 and held it, then stuck at 0, maybe just twitching a bit on the second and third try. The wet test gave me a 0 reading as well.

This was done pulling only 1 spark plug at a time.

My understanding of this means that I probably?? have something wrong with the valves?

My big question is do you guys think that's the problem too? If so is there any other tests I could do? And lastly if it is a problem with the valves how do I go about fixing them? Is there any writeups out there?

Thanks in Advance

 

[red91]

how did the plugs on the bad holes look ? Wet and oily or dry ?

 

[Beached Bones]

When I initially changed the plugs they all looked pretty normal and dry. The engine had not run since the day before. When I pulled out the new one from cylinder 4 while doing the compression test it was a little wet. Right before the test I was running the engine for a while picking up the tester and checking some other stuff out.

 

[red91]

better dry than wet. Never done a head on a jeep though... SOMEONE will chime in. I don't think it'll be too bad.

 

[Eagle]

Two things can cause zero compression -- a valve stuck open, or a piston with a hole in it. Either way, you should pull the head to inspect and diagnose.

 

[Beached Bones]

Two things can cause zero compression -- a valve stuck open, or a piston with a hole in it. Either way, you should pull the head to inspect and diagnose.

Can I check if a valve is stuck buy just pulling the valve cover and looking?

 

[Beached Bones]

I pulled my valve cover, and the rear rocker for the #4 cylinder is loose to the point it rattles it might have a hole worn into the bottom because it's the only rocker that doesn't have a little puddle of oil in the middle of it.

Anyone know what this means? it is the cause of the problem? or a secondary effect? any help would be great.

 

[Beached Bones]

I ran the engine with the valve cover off, the rocker on #4 doesn't rock, the pushrod occasionally just taps it making a clicking sound. the pushrod isn't tight and if I push it down into the engine it feals like it's sitting on a spring, one much weaker that the valve spring so whatever is pushing on the pushrod is weaker that the valve spring?

this just doesn't make sence to me

I've been serching, does collapsed lifters make any sence?

 

[Eagle]

I've been serching, does collapsed lifters make any sence?

No, because a collapsed lifter wouldn't open a valve. Even if the intake valve didn't open, there should be SOME compression. It sounds more like the valve is stuck open. Can you eyeball it, and see if that valve appears to be at the same height above the head as the ones adjacent to it?

BTW -- if it is a collapsed lifter, you still have to take the head off, because you can't get the lifters out with the head in place.

 

[Beached Bones]

I can lay a straitedge (pen) accross the valveprings to both sides (#4) and it is flat. All the springs look about the same height except for the last valve on the end #6 cylinder. It is fully compressed (valve open)

 

[4Banger]

Is the #4 rocker loose because the bolt is loose or the rocker broken, worn? Can you move it by hand?
Did you rotate the engine by hand (pull the plugs, makes it much easyer) to check for any valve movement? Esp. @ #4.
Have you tried a leakdown test?

 

[Beached Bones]

Is the #4 rocker loose because the bolt is loose or the rocker broken, worn? Can you move it by hand?
Did you rotate the engine by hand (pull the plugs, makes it much easyer) to check for any valve movement? Esp. @ #4.
Have you tried a leakdown test?

The bolt on the rocker is tight and properly torqued. the rocker is loose to the point i can move it a bit to both sides, up and down. I have swapped rockers to test, and any rocker in that spot is loose. it seems that there is not any pressure coming from the push rod, it sits lower that the others, has some space between it and the rocker, and when i push down on that push rod, i can feal a spring (I am guessing in the lifter) and some squishyness like a small blown shock.

What is seems like to me now is that the lifter check valve is gone, so there is not enough force transmitted up the pushrod to the rocker. In turn the intake valve is firmly planted shut not allowing any air in so I'm getting no compression.

That's for cylinder #4, I see anything wrong for sure with #6. with that one the rockers are at least rocking.

 

[JJacobs]

Just pull the head. It only takes about an hour on a 4 litre, and you'll have to pull it to replace lifters anyway.

How to go about getting a more accurate diagnosis: Do a leakdown test, or at least use a gauge with detachable hose so you can pressurize the cylinder without necessarily using the leakdown gauge set. You'll need to have the cylinder being checked at TDC on the firing stroke, or during the firing stroke just after TDC. Best bet is to rig a breaker bar with a socket on the crank to hold the engine so the air pressure can't roll it over. Once everything is locked in place apply air (slowly in case the bar slips off!) and listen to the airbox, exhaust pipe, and oil fill cap to determine the problem area.

If the problem lies in the valves try tapping on the valve stems with a brass hammer while the cylinder is pressurized. If carbon is the problem, this will shatter it and blow the pieces out. Used to do this on motorcycles all the time.

I doubt carbon is your problem though. I don't think it's the lifters either. Even if a lifter is not pumping up, the height of the cam lobe is more than the amount of lifter internal travel, guaranteeing the valve will rise off its seat. Case in point, an engine with brand new unprimed lifters will still start up, and simply run loud for a minute until the oil goes where it needs to.

I'm thinking either flat cam lobe or burned exh. valve, either way time to pull the head.

 

[jeepcherokee95]

One thing no one has mentioned here yet is a broken valve spring! I have never had the cover off of my 4.0 so someone will have to enlighten us - are the springs dual springs or single? If dual then the inner spring could be broken and not allowing the valve to open and intermittently "hitting" like he stated.

If not the springs then I would agree...Pull the head and check the valves. Try the leak down test first though its cheaper!


JC95

 

[JJacobs]

4.0's use a single spring stock. Good think'n though.

 

[explorer]

Single springs on the valves. Sounds like a flat cam lobe. Turning the engine over by hand, watch the travel of the pushrods. If the cylinders that have low comp. are not moving as much as the others, the cam lobes on those cylinders are probably worn. You have to remove the head to really see them, so some disassembly is in order. The lifter has a small amount of travel. Even if the lifter is not pumping up at all, the valve will open.

 

[Beached Bones]

I don't think the cam is too bad, the pushrod moves pretty good if there is no resistance on it, but if there is any resistance the lifter seems to absorb the movement. There is a good 3/8 inch of play from the lifter. I can easily compress it enough to get my finger between the rocker and the pushrod, or between the rocker and the spring. All the valvesprings appear unbroken. I think it should be pretty obvious if one was.. right?

I did another compression test on the two bad cylinders. today #4 twitched the guage up a bit but still kept it in the zero range. #6 pumped up to 110 psi and held it, after a long period of cranking. second time only made it to 35 psi, third time about 10 psi

I know some don't aggree with me, but I am pretty convinced that the prob with #4 is just the lifter, #6 is likely burnt or sticking valve(s)

To fix this what parts do I need. I'm thinking
1) valve cover gasket
2) head gasket
3) at least one lifter
4) intake and exhaust valves for cylinder #6
5) locktight for head bolts
6) teflon pipe dope.
7) new set of pushrods if they aren't too expensive
8) valve spring compresser

Questions
Do I need one of those "lifter removal tools" that I've heard about?
What do I look for when the head is off to figure out if/which valve(s) need replacing?
Do I need to remove ALL the valves and valve springs before I take the head off?
Do I need a special tool to unhook the fuel lines?
How heavy (guestimate) is the head and exhaust manifolds to remove together, or is it better to remove the head by it's self? It looks like alot of metal there.
Will to do much more damage to wait a month until I get some vacation time to work on this?
I still need some sort of write up on all this, having never done this before I REALLY doubt it would take me an hour, it would probably take me that long just to drain the coolant, oil and get the connections marked where they belong. I need to know what to do and what to expect, and how much its going to cost before I rip the engine apart on my only means of transportation.

 

[JJacobs]

It's not hard to lift the head out with the manifolds attached. Two man job, but doable, and you'll probably find it's easier to remove the manifolds from the head out of the vehicle, if you even need to take them off.

Burned valves should be really obvious. Less obvious is a cracked head. I had a 4.0 head with cracks across 5 of the 6 bridges between the valves. You can pour solvent in the ports or the combustion chamber depending on if the manifolds are off, and watch for leakage.

No special tools required to get the lifters out once the head is removed.

I'm not sure if you'll need special tools for the fuel fittings for your 92. On a Renix motor they come apart by hand and new o-rings from the dealer are recommended.

Make sure you inspect all the bores with the head off, and run each piston to TDC and check for major side play.

 

[Beached Bones]

For anyone interested this is how things turned out.

I did the work last weekend, 7 hours the first day to pull it all apart and clean the gasket surfaces, and another 7 hours the next day to put it all back together again.

I pulled the head and manifolds together, using 4 * 500lb ratcheting tie downs strung up to the rafter in the garage. This may have been a slower way to do it, but I found the control I had over the head both removing and installing to be a big help. I had no worries about dinging the head gasket when putting it back into place. I could position it a couple inches at a time in any direction, and used the “chevy pushrod trick” I read on this board a while back to align it the last couple inches. I had to substitute the “chevy” pushrods for old jeep ones but luckily it worked anyway.

In short I replaced the set of lifters, all the pushrods, headgasket and valve cover gasket. My exhaust down pipe gasket was not stock and in good condition so I reused it, rather than hunting down a new one.

Taking it apart I confirmed that the intake lifter on #4 was shot… it was worn so badly that it had developed a hole right through the seat of the lifter. I have quite a bit of carbon buildup across every cylinder, with more one the two original problem ones. I cleaned what I could with carb cleaner and dishpan scrubbies, but I didn’t get too carried away because I really didn’t want to mar the surfaces. The headgasket looked Ok to me, granted I’m no expert and it was mangled pretty bad coming out. (half stuck to the head, half to the block. There was some pretty good wear on the pushrods, not unexpected at 250,000 KM.

It runs much better now, and I checked compression again.

First time I got in order 130,145,140, 0,140,0-60
Second time I got 126,140,139,140,139,136

To say the least I’m pretty happy with myself about that.

My jeep still miss fires a little, I have new cap/rotor plugs, have spark and can hear the fuel injectors tapping. I think maybe my fuel injectors are a little clogged because off the carbon so I’ll run some injector cleaner through the next couple tanks of gas. The jeep is still spitting out some carbon I loosened up so maybe it’ll pass when it passes more of that.

Anyway, Thanks to everyone on the board for your help, both direct, and indirect from your postings on the board!