Engine/Transmission (1994 - 1998) Valve seal question

[Bobcat698]

I posted this bit of text a while back on DTR:

"Truck has been sitting since Friday night after I popped both driveshafts & the transfercase.



Anyways, I pulled the turbo off as I am replacing it with a newer model.



When I took it off, I saw that there was some oil residue in the exhaust manifold. . Enough to be wet on my fingers.

It was from the front 3 cylinders (combined)



Any idea what this would be from? (yes, I know its from the engine, but why??)



Thanks!"



I just got the head off today and noticed this:

The valve seals were NOT set at the bottom of the valve spring, but rather they were in a midway position (middle of the valve)



That isn't normal, is it?



Is it possible that whoever installed the seals did it WRONG?



Any input?

 

[Vaughn MacKenzie]

I remember reading something about this before, but it seems the seals on 12 valves tend to walk up the stem sometimes. As I recall 3 or so of mine were that way on my '96 at 352k when I did head work.

 

[Bobcat698]

It seems like ALL of mine had walked up in only 25k miles, the seals were all redone the last time I had the head off.

 

[Vaughn MacKenzie]

I don't think the seals are as critical as on a gas engine, being the valve pocket area doesn't see nearly as much vacuum due to no throttle plate. As long as the guides are good you shouldn't be pulling too much oil through here.

 

[bgilbert]

Did it smell any like diesel fuel? Leaking injectors will do this too. I had a similar issue with a donor engine and according to the Cummins trouble shoot thinking, valve seals were almost last on the list of possible sources of the oil/fuel crap on your fingers. I don't have the book here, but leaky injectors, obstructed turbo oil drain, turbo seal leak, headgasket and others were higher on the list.

 

[AFarmer]

Did you ever check your drive pressures on the setup that you were running?? That could have certainly been a contributing factor to pushing the seals.

 

[paulb]

This is a fairly common problem. Cummins even makes a valve seal that has an integrated spring seat, to keep this from happening. I have them on my head, but I do not have any idea what the part number is. Higher combustion pressures, and higher drive pressures, can make the seals "work" up the stem. One thing to remember is that loose valve guides can also cause the problem, because of the extra clearance between the stem and the guide, allows more air to be forced up the stem. Replacing the seals is only a crutch in this situation.



Paul