Jeep 4.0 valve leak - machine shop?

[DAA]

Trying to diagnose a cylinder 6 misfire at idle which has gone from occasional and mild to constant and nasty. And also gone from not being noticeable except at idle to being noticeable well off of idle too. Did a leak down test last night. Cylinders 1 through 5 all between 5% and 8% leak down. Number 6 is 80% leaking down. Air is coming out the exhaust.

So, exhaust valve issue there.

I don't know exactly what to look for, or what might have caused it. A lifter? A spring? Something else? I really don't know. My plan is to take the head off and see what I can see. Any advice on proceeding, what to look for etc., is appreciated.

And, presuming I'm going to need at least that one valve replaced. Any recommendations for a machine shop? Thoughts on leaving the rest of them alone and only replacing what I find messed up? I'm kinda thinking with most of the others only leaking down in the 6% range, the motor is generally pretty dang healthy and no sense monkeying with it. But, I don't know anything about doing engine internals. So again, any thoughts or experienced advice is welcomed.

Thanks!

- DAA

 

[UNSTUCK]

Don't just jump straight to removing the head. With the valve cover off you will learn a lot. Broken spring, maybe a messed up keeper, maybe see a bent stem. Are you burning oil too? That would lean me towards a bent valve stem as well. Or the top side might be perfect and you have just burned up the valve, in which case you'll need to try to figure out why.

As far as machine shops, I have used The Love Machine co. many times for large diesel engines with great success. Never a smaller engine though. I'm sure they'll do it for you. I'm not sure if they will only play with one valve. I've never heard of anyone doing that. They will likely want to disassemble the entire head and run it through all their tests and then clean it all up. So a full head rebuild.

How many miles are on the engine? Have you looked at purchasing a new head? If the miles are high it might be time to consider a new engine. Or at least look the cylinders over very closely when you take the head off. Sometimes an engine swap becomes easier than diving deep into an engine.

 

[DAA]

It's not losing any oil. A 2006 I am the only owner, with 110,000 miles, never had to add any between changes at every 4,000 it's whole life.

Up until just the last week or so, even with the misfire at idle, it has been running great. No noticeable loss of power or MPG, just a noticeable misfire at idle which the CEL told me was on cylinder 6. It used to be very intermittent, only did it once in awhile, was not even noticeable except at idle and never lasted, the CEL would clear itself. Now it seems here to stay and it suddenly got a lot worse and noticeable at well above idle.

I haven't looked into a new head or anything like that yet. But, I have been thinking about the possibility of a new reman engine vs. going really deep into this one. If say, for instance, it needs a cam and lifters, and a head rebuild. It might be smarter to just swap in a new rebuilt motor? But, I don't think I'll know that until I'm pretty deep into it anyway. Kinda thinking the cam might be the pivot point that helps me decide which way to go there. If it's good and I can get it well again with just removing, repairing and replacing the head, maybe lifters on the old cam, I think I'd go that route and save a ton of money vs. a new motor. But, again, I really don't know, this is not familiar territory for me.

Did a compression test a couple months ago while also messing with this misfire (I ended up thinking it was the coil rail, and thinking I had fixed it). At that time they were all at 140 - 145 psi. That and the leak down test last night, I think the motor is overall in pretty good health?

Not to derail my own thread, or complicate things too much, but this does complicate things in my mind... But I think my NSG370 six speed manual transmission has an input shaft bearing trying to shit the bed too. Every once in awhile, it makes a really bad tapping sound. Not very often and only after being run hard for awhile. I always suspected the noise was related to the misfire. But it never made that noise at a time and place I could easily try and really figure out where it was coming from. Well, it did it at home the other night, so I put the stethoscope on it and think it is probably coming from bell housing, not from the motor. Noise stopped when I pressed in the clutch too, which I somehow never noticed that part before. Google says those symptoms most likely an input shaft bearing.

So... This whole shit sammich is getting kind of complicated for my simple mind. If I have to unbolt the transmission to get it fixed or replaced anyway, then half the battle of pulling the engine is done. But I can also see if I can get away with only dealing with head removal on the engine, I might just run that transmission until it's not just a noise that it makes once in awhile and I have to spend the money. Or, tackle it all at once, now, which is probably the smarter path. Just hard on the budget and not a good time for my Jeep to be down for very long. Is what it is though.

But yeah, my next help thread will probably be asking about transmission shops...

- DAA

 

[Gravy]

Gordon Johnson on 200 W. in Bountiful has done a couple heads for me. He matched a head to new stainless valves with heavier springs on a Yamaha and the price was decent too. He's an old crusty curmudgeon but I kinda like that ha

 

[DAA]

I'm turning into an old crusty curmudgeon.

- DAA

 

[RockChucker]

I had Clegg Machine do my Duramax heads when I did head gaskets a couple years ago. They did a great job.

 

[UNSTUCK]

I'll bet you a dollar your transmission noise is the throwout bearing and not internal. That's just a clutch job that it may well be due for anyways. But yes, you're still separating the trans and engine.

Probably best just to go LS and an automatic. Your old crusty curmudgeon leg is probably tired of the clutch pedal.

 

[mbryson]

I'll bet you a dollar your transmission noise is the throwout bearing and not internal. That's just a clutch job that it may well be due for anyways. But yes, you're still separating the trans and engine.

Probably best just to go LS and an automatic. Your old crusty curmudgeon leg is probably tired of the clutch pedal.

LS swapped LJ!!!! Does it get much better than that?

 

[DAA]

I'll bet you a dollar your transmission noise is the throwout bearing and not internal. That's just a clutch job that it may well be due for anyways. But yes, you're still separating the trans and engine.

Probably best just to go LS and an automatic. Your old crusty curmudgeon leg is probably tired of the clutch pedal.

Put a new clutch and TO bearing in last winter. Clutch had much life left in it but TO was toast, so did it all while apart.

The noise it's making doesn't sound anything at all like any TO bearing I have ever heard. It's like a little dude with a hammer in there trying to get out. But, that would be awesome if a TO bearing is all it is. Hope you are right!

I love the clutch pedal. My crusty old curmudgeon leg gets pissed off every time it drives anything without one. I not infrequently put my left foot down on the empty spot on the floor of my truck and reach over to the empty space above the console and start thinking WTF? Before remembering, automatic. All crusty old curmudgeons love clutch pedals and get pissed when they are missing. If they don't, they are fake crusty curmudgeons.

That said... I'd love me some LS. Love, love, love. Would even give up the clutch pedal for some LS. Curmudgeons love V8's more than they love clutch pedals. Budget says "not at this time" though .

I am going to take your advice and just start slow with getting the valve cover off. Might get lucky. Never know. Getting lucky has never been my style though. So, assuming I am going to be taking the head off and looking at a burnt valve. What concerns me most, is trying to figure out what caused it and fixing whatever that is to prevent it from happening again. Just don't know what to look for, really.

- DAA

 

[UNSTUCK]

LS swapped LJ!!!! Does it get much better than that?

I may be a little biased suggesting that because that IS my dream Jeep.

 

[UNSTUCK]

https://ssch.com.au/trade-news/a-basic-guide-to-engine-valve-failure/

After you remove the valve cover, turn the engine over by hand a few times while watching the #6 valves move.
As you watch the exhaust valve:
1. do you get movement that resembles the other 5 cylinders' valves?
2. does the stem close as high as the others do (try to be exact)?
3. with the intake valve opening, can you wiggle the rocker arm of the exhaust valve?

Answering these questions will put you in the right direction without removing the head.

 

[DAA]

I will do exactly that then and report back. Was hoping tonight but more likely tomorrow night.

- DAA

 

[thenag]

If you do end up pulling the head and getting an exhaust valve done it probably won't be as expensive as you are thinking it will be. I am sure pulling the head on a LJ is much easier than an XJ. I just had a bent exhaust valve and could have had it repaired and the head milled/surfaced for about $150.00. I had him go through all the valves since it was on their work bench so it was more. Of course you end up spending money on head gaskets, head bolts and all kinds of other things so it is still an expensive job, but the machine shop bill might be less than you expect.

(I have a 4.6L with LS valves in an xj but I can't keep it cool right now...)

I used Clegg down in Orem

Nathan

 

[DAA]

https://ssch.com.au/trade-news/a-basic-guide-to-engine-valve-failure/

After you remove the valve cover, turn the engine over by hand a few times while watching the #6 valves move.
As you watch the exhaust valve:
1. do you get movement that resembles the other 5 cylinders' valves?
2. does the stem close as high as the others do (try to be exact)?
3. with the intake valve opening, can you wiggle the rocker arm of the exhaust valve?

Answering these questions will put you in the right direction without removing the head.

Just pulled the valve cover off. Squeaky clean in there, not a hint of sludge or any kind of build up or discoloration or anything at all. Looks brand new.

1. - Movement looks the same on #6 exhaust as all the others.

2. - This was difficult to measure with any precision. I used an inside caliper that doesn't have a scale between the valve cover seal surface of the head and the underside of the nose of the rocker, then measured the opening of that caliper with dial calipers. Which, BTW, on all the other 11 valves, I can measure directly and positively with the dial caliper, but the firewall is in the way of the dial caliper on the ONE valve I'm most interested in. But, anyway, not real precise, my measurements were only repeatable within about .030, which sucks, but #6 exhaust fell within the same range as the others.

3. - Can't wiggle it at any point in it's travel.

So, I'm thinking, not telling me anything? So, off with the head... Yay...

BTW, before tear down, just for grins, I tried the old dollar bill test at the tail pipe and it did indeed get sucked in on a regular rhythm. That, the leak down test, the now pretty terrible misfire, I'm pretty sure there's a burnt valve awaiting me. With any luck I'll have the head off by Saturday for inspection.

Kind of leaning towards just getting a reman head, if it comes to that. That's the most expensive option, probably. But I'm leaning that way mainly because I'm really hating on the prospects of extended downtime. Coyote hunting starts real soon and my Jeep needs to be ready to go. If I can get a reman in a week, or have to wait a month to get mine done, I'll have to pony up for a new one. Ten coyotes pays for a new head, lol! But, I'll call the shops you guys have recommended and try to get a feel for what the turn time might be first. I've just had generally really bad experiences with promised turn times vs. actual turn times. If a local shop tells me a week though, I'm there!

Appreciate all the help, really do!

- DAA

 

[I Lean]

When I had the head on my 80 worked over by Pro Machine, they told me 3 days. They had it done in one.
In my case they just milled it, pulled vacuum to check all the valves sealing, and installed new srem seals. But still, they work pretty fast generally.

 

[DAA]

Well now we're talking.

I'll Google it, but whereabouts is Pro Machine?

- DAA

 

[I Lean]

They're in Murray, around 4800 S and 500 W ish. They do a lot of Toyota work, but I'd be really surprised if they don't know their way around lots of other engines.

 

[Homefryy]

Clegg did a complete remanufacture on my 4.0 in a week last year.

 

[DAA]

All good to hear. This head so far looks to be in overall good condition. Seems kind of a shame to make it a core.

- DAA

 

[DAA]

So I had freshening up the cooling system on my list for the fall anyway. So I did a flush before starting, going to replace coolant, put in a new water pump and hoses etc. Been wanting to pull the radiator out for awhile, just because I knew what it would look like, and I was right.

Between that and the sage brush that gathers on the skid plate around the muffler, it's no wonder my Jeep always smells like a desert. A desert full of cigar smoke.

Felt good getting all that cleaned out of there!

- DAA