You guys scared me. We got the head off last night. Inside the engine (pistons, cylinders) looks impeccable - just a little carbon which we'll clean up. 142K and we can still see the cross hatching on the cylinder walls and virtually no wear ridge. We flip the head over and stare at the valves for a while and panic because they LOOKED fine. I pour acetone into the combustion chamber and around the valves, and boom... within a few seconds, it's dripping down the valve and out the exhaust port. Nothing horribly bad but definitely not sealing correctly. I think that explains why our compression test was OK but not the leak down. So, it looks like a leaky valve is the issue. Waiting on a new head from clearwater and we'll see for sure.
Looking for any help with the dreaded misfire issue
- Thread starter jimvski
- Start date
It always amazes me when I see the piston bores on the 4.0l. I've pulled 4.0ls engines apart at 200k+, where you could still see the factory cross hatching and there was no ring ridge. The most common issue is carbon deposit. I've also pulled them apart where I consistently used quality fuel system cleaners and the carbon build up was minimized. This doesn't look bad at all! Are you using new head bolts when you put it back together? Also, now's a good time to install new expansion (i.e. freeze) plugs, if you haven't already. Even the brass ones are cheap!
I've only torn apart a couple engines in my lifetime and was just floored to see the crosshatching. We've owned it since new and now it's my son's (he has the Jeep bug too). I've only used Mobile 1 and been faithful in our oil changes. We had the oil pan off and looked at a crank bearing and now the top end and everything looked great. I think after the new head goes on he'll essentially have a like new engine.
As far as new head bolts - yes. I also told him to order manifold bolts. Nothing like spending his money instead of mine for once. We have a trip planned next week so I probably won't tackle the freeze plugs. Going to be tight just getting it back together in time.
Again - I can't say thanks enough to everyone here. I've had a Jeep since 1995 and the Jeep community is the best. I was going nuts trying to figure this one out because I convinced myself it was electrical. This forum convinced me to consider the valves.
As far as new head bolts - yes. I also told him to order manifold bolts. Nothing like spending his money instead of mine for once. We have a trip planned next week so I probably won't tackle the freeze plugs. Going to be tight just getting it back together in time.
Again - I can't say thanks enough to everyone here. I've had a Jeep since 1995 and the Jeep community is the best. I was going nuts trying to figure this one out because I convinced myself it was electrical. This forum convinced me to consider the valves.
When i tore my block down i was able to soak it in some watered down acid and it cleaned up the ports/jackets for cooling.
Well, the saga continues. Have a trip in 2 days and we have a new head from clearwater. New bolts, gaskets, etc. we were putting the head on and for some reason a head bolt snapped when going to the final 110 ft lbs. so, we took it apart and spent the night finding new bolts and a new gasket. We’ll try again tomorrow.
we torqued them per the service manual. 22, 45, then 110. The broken stub unscrewed easily. The holes were dry and looked clean. Does anybody have an idea why it might have broken? I can’t have something go wrong tomorrow…. We’ll run a tap through them and then test fit the bolts first but can anybody offer any other suggestions for a smooth assembly?
we torqued them per the service manual. 22, 45, then 110. The broken stub unscrewed easily. The holes were dry and looked clean. Does anybody have an idea why it might have broken? I can’t have something go wrong tomorrow…. We’ll run a tap through them and then test fit the bolts first but can anybody offer any other suggestions for a smooth assembly?
it wasn't the bolt that goes in the water jacket correct? that one is only suppose to be torqued to 100 ft lbs. I usually put a bit of anti-seize on mine.
No. It was bolt #5 I think. near the center of the head - I was shocked it happened. We had torqued several others and this one broke.
always replace the bolts with new ones. however if you have no choice tap that baby out and put one of the old ones in there. I had to do that recently.
What brand of bolts did you end up going with? Both times I’ve taken the head off I’ve used felpro and they’ve worked pretty well so far
Yep - they were brand new. My son was doing the tightening so it's possible he wasn't real smooth but they shouldn't have broken. We now have a second brand new set and a new head gasket. It's going together one way or another today. I'm going to run a tap through the holes to make sure they're clean, then we'll blow out the holes. Then we're going to run the bolts in to the bottom to make sure they're not binding. Trying to decide if I should lube the bolts or not - I've seen varying opinions. Fingers are crossed this goes well.
We had Fel-pro. I've used their stuff for almost all my gaskets and been very happy. I really am struggling on why this happened. Hopefully just a fluke/defect.
Also i know this might sound stupid but get a light in the hole check for anything. Then get your tap and run it to make sure threads are good. BUT also go ahead just to make sure its all good and measure the depth of the hole the tap goes into. Never know.......could be slightly more shallow.
Thanks - will definitely do that. What's even crazier is when we took the head off, what was left of the bolt just unscrewed by hand - didn't even need pliers. So, I don't think it was binding or bottomed. I'm hoping just a defect and with the second set we'll have plenty of spares if it happens again.
WHOO HOO!!! Head is on. Now to assemble the rest and see if/how it runs.... lol
One last update. We got the head on and Jeep reassembled/running at 11:00 PM Wednesday night. Left on a 6 hour trip Thursday at 8 AM. Got to our destination, spent 2 days off-road and then drove it back. I was a little nervous the whole time but all went well.
A final thank you to everyone for their advice/suggestions.
Jim
A final thank you to everyone for their advice/suggestions.
Jim