Jeep 4.0 valve leak - machine shop?

[frieed]

not sure how that could get in there since that jeep only sees pavement

 

[UNSTUCK]

#3 is actually pretty interesting and could be telling. Did you compare that to the other rocker arms? Could you wiggle them with their valves closed? They should wiggle with a cold engine. Most inline engines (most all engines) will have .015 to .030" clearance between the rocker and valve stem when closed. If you can't wiggle the rocker that could mean that the lifter side is still holding the valve open just a bit. Even if it's just that .030" you're not sure about. Would hate it if you put on a new head and found the same issue because of a valvetrain issue. What's worse is that the valve could be burned up because of a valvetrain issue. So you may see the bad valve, but don't stop investigating if you do. Check the cam lobe, push rod, lifter and rocker arm, and any other small parts this engine may have.
Note: I've never played with this engine before so I don't know exactly how it should be. I'm speaking more generally.

 

[Greg]

#3 is actually pretty interesting and could be telling. Did you compare that to the other rocker arms? Could you wiggle them with their valves closed? They should wiggle with a cold engine. Most inline engines (most all engines) will have .015 to .030" clearance between the rocker and valve stem when closed. If you can't wiggle the rocker that could mean that the lifter side is still holding the valve open just a bit. Even if it's just that .030" you're not sure about. Would hate it if you put on a new head and found the same issue because of a valvetrain issue. What's worse is that the valve could be burned up because of a valvetrain issue. So you may see the bad valve, but don't stop investigating if you do. Check the cam lobe, push rod, lifter and rocker arm, and any other small parts this engine may have.
Note: I've never played with this engine before so I don't know exactly how it should be. I'm speaking more generally.

Excellent advice, IMO. Keep digging until you're 100% sure what the failure is.

 

[DAA]

Got the head off. Exhaust flange bolts gave me fits, considered just leaving them on with the manifold hanging off the side. But wanted to make sure I could get them apart at a later date if needed, and wanted to be able to tighten them up more easily too. Pulled the manifolds off the head and got the intake out of the way so I could go at the flange bolts from the top. Went and bought a pass through ratchet which I could get on them nice and square without interference from the precats and they gave up pretty easily at that point.

Pulled the rockers and push rods. They all looked good to me. But I wouldn't claim to know what I'm looking at.

These are #6.

Head off, looking at #6.

Well, huh... I guess I don't know what a burnt valve looks like. But that doesn't look like anything to me. That #6 exhaust is a bit different color, but there are a few colors going on in there. #6 piston is a bit blacker than the rest. Ought to be, been misfiring like a mother just lately.

I'm not brimming with confidence at this point...

Decided to fill the combustion chambers with water and see what happened.

Sat there puffing on a cigar watching, nothing happening I could see, starting to get discouraged, when this started to flow from #6 exhaust.

#6 exhaust was pretty well empty by the time I was done with my smoke break. None of the others appeared to leak at all, they were all still full and the ports dry.

So... Head is going to Cleggs in the morning to get a rebuild. They said probably end of the week. Not going to hold them to that, early the following week is okay, but it would sure be nice to be reassembling by next weekend.

But! Now I HAVE to figure out what cause this.

To me, and again, I don't really know what I'm looking at, but the rockers and push rods look great. Push rods are all straight, all look like peas in a pod as far as wear - some visible, but not much.

I need to look at the lifters. Started on them with one of those cheap checks stand cardboard rack magnets you use to fish bolts off the skid plates but could only get a few of them out with it and not #6 exhaust.

Any tips on lifting out lifters would be greatly appreciated!

- DAA

 

[DAA]

#3 is actually pretty interesting and could be telling. Did you compare that to the other rocker arms? Could you wiggle them with their valves closed? They should wiggle with a cold engine. Most inline engines (most all engines) will have .015 to .030" clearance between the rocker and valve stem when closed. If you can't wiggle the rocker that could mean that the lifter side is still holding the valve open just a bit. Even if it's just that .030" you're not sure about. Would hate it if you put on a new head and found the same issue because of a valvetrain issue. What's worse is that the valve could be burned up because of a valvetrain issue. So you may see the bad valve, but don't stop investigating if you do. Check the cam lobe, push rod, lifter and rocker arm, and any other small parts this engine may have.
Note: I've never played with this engine before so I don't know exactly how it should be. I'm speaking more generally.

I couldn't wiggle any of the rockers. There's no lash adjustment on these though. On reassembly you just torque the cap bolts to spec.

Now that I've confirmed #6 exhaust is leaking and the head will be going to the shop, I DO need to figure out what caused it. Like I said above, don't know what I'm looking at, but I don't see a smoking gun looking at the rockers or push rods. Need to get the lifters out. Have a sinking kind of feeling that lifter for # exhaust is going to look like the rest though.

Strongly considering replacing all lifters, just on GP. The motor wasn't making any lifter noise though, might be better to let quiet 4.0 lifters alone .

There is an old Chrysler TSB on these motors floating around out there, I've known about it a long time. Gist of it is, make a regular habit of running the motor at least 3200 RPM to keep the lifters turning in the bore and avoid carbon build up, which, according to the TSB, can lead to - burnt exhaust valves.

I do make a habit of running this motor up to over 3200. I run it to 4K through at least two, usually three gears every time I get on a freeway onramp. And sometimes cruise for long periods right at 3200 RPM, which is 80 MPH. But, I also make a stronger habit of spending whole days, hour after hour, at low RPM putting along offroad.

I don't see a lot of carbon there. I don't think I'm ready to buy that as my explanation. But, it's a possibility I guess.

Need to get #6 lifters out for a peek. I'll mess with them tomorrow.

- DAA

 

[DAA]

One more thing... I'm getting too old, skinny and weak to be grabbing heads off by myself like that.

- DAA

 

[BCGPER]

Since it’s leaking sitting on the bench I would bet your push rods and lifters are good. Run to Autozone and borrow a valve spring compressor and pull that valve out and see what it looks like.

 

[UNSTUCK]

Lots of interesting things here. Too bad there is no smoking gun. It's all speculation at this point. You definitely don't have a pushrod or rocker issue now, so you've narrowed that down. I'm guessing now you have a crack in the valve or head causing the water to leak through.
I didn't think about it till now, but it would have been nice to run a quart of water or seafoam through the intake while running the engine. That would have cleared up any carbon that could be sitting behind the valve, holding it open.

I would consider getting your injectors flow tested while you have all this apart. It would be good to know what #6 is doing compared to the others. New spark plugs should go in as well.

 

[DAA]

So I did do the seafoam while it was running. Well, Mopar top end cleaner anyway - same concept. A few days before my first post in this thread. Here's the interesting thing about that. It immediately started misfiring MUCH worse after the top end cleaning. Much! Went from noticeable at idle but not noticeable above idle, to stumbling badly at idle and noticeable up to about 1500 RPM. Almost like carbon had been what the valve was partially sealing on. That's when I decided to get a leak down tester and dive in.

Another clue, maybe. The misfire has been intermittent for a long time and I actually thought I had fixed it with a coil rail at one point because it went away for a couple of months. But when it came back, it was worse than before and didn't seem to want to go away. I had that old TSB in my mind, so I took it out on the freeway and flogged the holy living piss out of it. Ran it at over 4K for about ten miles. Get off the freeway and it's idling perfectly smooth, misfire was gone. That worked a couple of times, just run it hard as hell and the misfire would go away - for just a little while. Then it came back a bit worse still and wasn't going away. I started trying to figure it out (again) and hoping it would be as easy as new plugs and a top end cleaning etc. But, obviously no luck with any of that.

Was casting a beady eye on those injectors just yesterday. Intake is laying on the floor and it would take literally just seconds to remove them right now. Thinking of taking the cheap ass route on them for now - switch #6 with #1. But I should at least investigate flow test/cleaning.

 

[DAA]

Since it’s leaking sitting on the bench I would bet your push rods and lifters are good. Run to Autozone and borrow a valve spring compressor and pull that valve out and see what it looks like.

That would have been interesting. After I posted last night though, I had to get a shower and go feed the family. Head is going to Cleggs in a couple of hours here.

Going to get the lifters out today. I don't think any of them are stuck. But they are deep in the block, hard to reach with anything like pliers and my weak magnet isn't getting most of them out. They don't have any inner lip on top I can hook onto to grab them either. The removal tools that require first popping off the keeper springs and the top of the lifter would suck for this, because the lifters are so deep. But, like I said, don't think they are stuck so I'm sure I'll get it figured out.

Thinking if cam looks good to go, I'll drop all new lifters in after all. I'd like NOT to. But I'm not wired that way. Cheap parts, tons of labor to get to, gonna have them out anyway, ehhhh, yeah, I'll probably put new ones back in. And then they can start making noise in a month and I can have a good Told You So moment with myself...

- DAA

 

[thenag]

So... Head is going to Cleggs in the morning to get a rebuild. They said probably end of the week. Not going to hold them to that, early the following week is okay, but it would sure be nice to be reassembling by next weekend.



- DAA

Clegg had mine for about a week in July, they said about a week and it took about a week.

 

[UNSTUCK]

Hard call on the lifters. I think they are fine. Your valvetrain is tight, not loose, which is what a bad lifter would do or a flat spot on the cam. You'd hear it tick when running.

You'll know soon enough when they tear into it. At this point I'd hope for a crack in the valve.

 

[Hickey]

I've got a good head in my garage for ya. It came off of my sons motor at 32k miles when the block asploded.

 

[DAA]

Dude, that is very much appreciated! My head went to the machine shop this morning though. Who knows though, maybe they call me next week and tell me it's cracked.

Got the rest of the lifters out easy enough. I was wrong when I said there isn't a lip. Upon closer inspection, there is a tiny groove near the top for the keeper springs. Used a pick in that groove and a pair of long needle nose and plucked them all out no drama. They all look great. Old No. 6 looks just like the rest of them. Cam lobes, as much as I can see from above, look beautiful.

Clegg's have been really nice to work with, too, BTW. Thanks to you guys for the recommend. They aren't even open today. But when I called late yesterday and explained, the guy said he could be there this morning so I could drop it off. Which I did of course. And we got to jawboning a little bit and upshot is he said he'll make sure it gets done this week, probably on Wed. he said. I'll bring seals that come in my head gasket set with me and they'll pop them on then.

So... If the head doesn't turn out cracked, should be able to put it all together next weekend. Still don't know what caused the burnt valve of course. Hoping the machine shop finds the smoking gun. Cracked valve like you guys have said, would be nice (at this point).

- DAA

 

[gijohn40]

Just out of curiosity what do your cylinders look like?

 

[DAA]

Just out of curiosity what do your cylinders look like?

Look really good to me. No scratches or scuffs. Can still see cross hatching. Not enough ridge to catch a fingernail. It compression tested dry at 145 psi a couple months ago. I think the cylinders and rings are good to go.

- DAA

 

[DAA]

Got all back together. Put about 50 miles on it, so far, so good. Idles very smooth and quiet. No new noises. No leaks. Smells all burned off. Oil is staying where it should. Running maybe a needles width cooler on the idiot gauge than before. Today isn't the hottest day to test, but full blast AC at low speed didn't cause it to warm up at all, which it has been causing it to slightly for a LONG time. On fire up, it wanted to get warm though. Brand new thermostat wasn't opening. Pulled it out, put it and the old one in a pan on the stove. Old one opened, new one didn't. Old one went back in and all is well with the world. Will put a couple hundred miles on it and change the oil then beat it just like always and see what happens.

We'll just have to see how it holds up.

Machine shop said just a sunken valve seat. Said he sees that a lot on these heads. All new hardened seats now, should be good to go for awhile.

- DAA

 

[gijohn40]

what was the machine shop price tag?

 

[DAA]

$345 out the door for a works job. It was done on Wednesday. Clegg was easy to work with. Good experience.

- DAA