6.9 motor problem diagnosis

Leroy

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Hi,

I'm wanting some advice on what directions to look in when repairing my motor. I think I will be pulling the heads anyway, they're very weepy and it could be just a head gasket failure, but I don't know, and any advice would be appreciated.

I've never had any problems like this, internally with the motor, and the symptoms are confusing me.

hopefully someone has had some similar issues or just some ideas to help figurin' just what's goin on here..

It's been goin' on about 4 weeks, started by sounding like an exhaust leak, with one extra pop out of the exhaust and a steady, annoying misfire. It got a little worse and I started noticing a pop also from the intake, when I lift the air cleaner lid 1/8 of an inch, it sucks it down and pushes it back up with the rythim of the engine. I can feel the air chuffing back out of the intake manifold.

It's getting too bad to drive now, but I have horded supplies the last few weeks and a little money, so I am taking this time to fix it. Going to tear her down and get to the bottom of it before something breaks.



I thought it was the head gaskets, they are certainly leaking alot, but then again they have been for along time. so I'm not really sure at all. It's 'chuffing' or 'popping' out of BOTH the intake and the exhaust. like an exhaust leak out of both sides. so I was thinking maybe a break in the gasket between 2 cylinders causing the cylinder pressure to escape to the neighboring cylinder when it was in the intake valve open stage.

but I have no Idea, could it be a bent intake valve, a lifter, would it pop out of one or the other and not both?

I'm trying to narrow things down what this is as much as I can. I took off the valve covers and run it, all the rockers and springs APPEAR to be okay.

I didn't hear any chuffing back up at the springs. everything looked okay visually.

Is a bad lifter capable of doing something like this? I know each set of rockers is tied together, but could one bad lifter affect the sister valve like that.

the sound is pretty much impossible to pinpoint, it seems to be coming from inside the motor, but reflecting out through the exhaust and intake.

Probably not, IDK at all, could this be a very strange injection pump issue? I doubt it just thinking out all the possibilities, it's not smoking or stalling like l'd expect from a typical IP problem, but has anyone experienced symptoms like that.

I have my old IP, it ran, smoke and stuttered, but it ran, and didn't cause any chuffing or knock. so I think I'll put it back on first to make sure it is still misbehaving in the same manner, so that at least I'll know that it's in the motor and not a fuel delivery problem.
loosening individual injectors yeilded no noticeable difference in running.

Probably a busted HG, I guess I'll probably be able to find visual indicators of what's wrong when I pull the heads.

another clue though, day before yesterday, after stopping about 10 minutes, at startup, it ran about 5 seconds, then COUGH run run run COUGH, like someone stuck a 2x4 in the cylinder, hard feelable miss, then it started knocking, like a bottom end knock.

I shut it down, expecting disaster, said a little prayer, fired it up and she was doing fine again. what could cause a knock knock knock like that?

It has been doing this last few startups, usually just in the mornings and not as bad, but it feels like half the motor is 'catching' or firing, then after a few seconds it finds it's pace and runs with all cylinders minus the misfire and shake.

I've never had to open her up beside external engine repair, this doesn't look like a fun job getting the heads off with as little room as there seems to be in the engine bay. I will be reusing the head bolts and valley pan gasket, I know.. got some permatex aviation form a gasket, is that the best for this job or would for some reason rtv be better in this situation.



no overheating or smoke, yes to much oil seeping.

if/ when I pull the heads is coolant going to dump down into the engine if I don't drain the radiator some?

Should I drain and keep the oil and coolant separately, as they're recently changed and still good, except for a little oily in the coolant, but not so bad, i'd like to keep the fluids, and will drain them if head removal causes cross contamination.


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advice, tips tricks and recommendations wanted and appreciated, thanks . Leroy
 

DaveBen

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That is a very metal sound. My guess is valve or valves or lifters. There are too many things that cause these type of problems in diesels. Tear it down and show us what you find.
 

Garbage_Mechan

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A few random thoughts:

A compression check will help you know what to look for even if you still tear it down.
Reportedly Harbor Freight has an inexpensive kit that will work on our engines. Might save you more than it’s cost.
The chuffing out the exhaust is usually caused by an exhaust valve problem. The way it sounds like it progressed, it is possible the exhaust valve isn’t opening causing the popping in the intake when air that has no where else to go comes back into the intake when the intake valve opens.
 

frankenwrench

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I would try a touch of marvel mystery oil in the oil to see if you can free up a sticky lifter. May work, may not. I had decent luck doing this twice. But as mentioned before, it kinda sounds like it could be a valve problem. Either way, you seem intent on pulling the heads for more reasons than one so I would check both while they're off. Sticky lifter is easy to find with everything out of the way. And since you will have the heads off I would clean the heck out of them and check your valves for cracks or build up and if you are comfy with lapping them that never hurts either. Any time I pull a head it never returns without lapping or new valve seats. And even with new valves and seats I still lap them just to be sure. Then again I have a tendency of being redundant and overkilling everything as well. Lol. Let us know what you find!
 

Leroy

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You know, it does have a kindof upper metallic sound accompanied with the miss, so when I take the valve cover off, they are all going up and down, if it's a particularly collapsed lifter, it makes sense that it would pop out the intake when it opens. Is there any way to check short of taking it apart?

I was considering doing a compression and leakdown test kit, though I understand these connected through the glow plug holes, and my glow plugs are almost certainly warped, because I fried them 5 ish years ago and have only disconnected them. The motor injested one tip about a year ago, and since I had to drive it, I just run it till tear down.

Do you think I will be able to visually identify.a problem lifter? Likelyhood of camshaft damage from running it anyway, and is there a way to check the springs?

Thanks for your help
 

Leroy

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Yes, I will, and the heads need to come off anyway, no odometer, but I am certain I have put at least 3-400 k miles on her in 9 years. I live far out in the country and pretty much every day I leave is hours and hours of driving. it's been weeping oil for 2 years, and getting worse, I know can't go forever on the old head gaskets.

When it first started doing this, I did put 3/4 of a bottle of MMO in the oil, as I was also concerned about a stuck lifter. Also ran a good amount of water in a sprayer bottle through the intake to bust up carbon that might have been sticking a valve, no different than before and after though.

I also add a quart or more of diesel the day before every oil change to clean lifters and internals, and let the dino sludge pour out smooth, I think that has prolonged the lifter life, but who knows.
 

IDIBRONCO

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I doubt that adding anything to the oil will do much other than waste time and money. My first thought was valves. Then I was thinking lifters. Then, realizing that it's a 6.9, if it still has the 6.9 style rocker arms, then you probably have issues with the aluminum pivots that like to break and are no longer made. Lastly, you say that you've put 3-400,000 miles on it and I'm back to the lifters. Either way, it sounds like you have head gasket issues so the heads will need to come off. When you pull the valve covers, you should be able to see any broken rocker pivots. Just get rid of all of the 6.9 style rocker arms and buy some 7.3 style. DEFINITELY install new lifters. With that many miles, they will be weak and may be the whole issue here. I suppose that there's a spec and a way to test the springs inside the lifters, but I'd bet money that they are weak. An exhaust valve that doesn't open will cause a popping out of the intake. An intake valve that doesn't open will just cause a dead miss on that cylinder since no air can get into the cylinder to burn the fuel inside it (no popping out of the exhaust). If your lifters or rocker arm pivots are bad, either one could cause a push rod to pop out from underneath it's rocker arm and cause the metallic sound in the top end when it hits the bottom side of the valve cover. This will usually leave a noticible dent in the valve cover. I would recommend pulling the engine out since this work is MUCH easier to do while he engine's on a stand. It all can be done with the engine is in the truck, but it's not as easy.
 

Leroy

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I have an engine hoist, but I don't have a stand, I do hate working in the engine bay because it's so cramped, is it worth the trouble to pull the motor? Maybe I'm thinking, is it much work to get it out with the t-19 bellhousing but trans removed? Anyone done it both ways and have opinions on what's going to be easier?

Like I said, I don't have a stand, but can find a tire, and timber to put under the motor mounts if that factors into it.

I pretty much have to do with what I got, because I cant risk driving it anymore, and have to stick to a tight budget. I can order a few parts as needed, but that's pretty much it.

Knowing of the weakness of the old style rockers, I replaced them with the updated style from a JY motor years ago, yes those old stockers were indeed badly worn, though these are new style and in good shape, I pulled a few suspect rockers and pushrods, though all checked out good on wear, and length and straightness so I put em back in.
 

IDIBRONCO

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I've never seen any point in making the engine longer by leaving the bellhousing attached to the engine. There's not much room for these to go in and out. The tire and timber would work fine. Yes it's definitely worth the trouble to pull the engine. A couple more reasons why. 1) these heads are very heavy. with the engine out, you can find a helper to help remove and install the heads. 2) with the engine out, you stand a lot less chance of damaging a head gasket. I've R&R'd heads on IDIs many times with the engine in. Usually, it was fine, but I have damaged a few head gaskets too.
 

Leroy

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pulling the motor does sound appealing, even removal of the valve covers is a pita in the truck, I will give it strong consideration, and probably will just pull it, thanks.
 

frankenwrench

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If you were a bit closer I'd let u borrow one of mine and an engine puller. Do as you will, but I have done in bay and pulled the block and put it on a stand several times a piece and the extra few steps definitely makes it easier for me. Them heads are heavy! Placing them gingerly just in the right spot is just as u said, pita.
 

Thewespaul

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I bet it’s just a rocker failure, I would pull the valve covers off and take a peak, it will be pretty obvious if there is a rocker failure. If you’re replacing one replace all of them with 7.3 rockers, and retorque the head bolts while you have them off.
 

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