Where'd my valve guide go? Help pls.

[soulbandaid]

So i was doing the valve stem seals today on my 84 300sd when i got to the cylinder nearest the steering wheel (furthest back) and the exhaust valve has no valve guide. On the three other cylinder the valve stem seals appeared to be good (which is strange because the car puts out a large cloud of white smoke every time it starts and through the first acceleration). On the back cylinder the intake stem seal was not seated at all and the exaust one was not only not seated, but worse there was nothing to seat it on!
The weird part is there isn't a lot of play in the valve. I would expect it to be pretty sloppy without the guide (confused)?
The car has obviously been the victim of so hack mechanic shenanigans judging by other fixes i have found throughout the car. \
Did the last owner/mechanic break the valve guide, remove it and put it all back together? Or is there something else that can happen to make a valve guide up and disappear (i hope its not in that cylinder). The car runs and sounds good so i'm thinking it isn't. Wouldn't it make some god awful sound?
Second, how thick is a valve guide? How much play should i expect from a valve that is missing its guide?
Third, what is the procedure for replacing a valve guide. My timing chain is good and i really don't wanna pull the cam. Can i turn the engine so the valve goes down most of the way (just before the valve would fall in), slip the guide over it, fish out the valve through the guide (with a magnet if need be), put a nut on it, turn the engine over again and reassemble? or is that not going to work for some reason?
Thanks in advance for all the help.

[barry123400]

I am trying to visualise this. It almost sounds as if there is no valve guide in the head for that valve. Since they are driven in to place with some force and reamed for the valve you might have to pull the head.

First make absolutly sure there is none there. Hard to believe someone would put a head on with a valve guide missing. Yet strange things are periodically found. It would account for that smoking though. No way the guide could drop into the engine either if you think about it. The head of the valve is so much larger. Depending how long this has been the situation I wonder what the valve seat is like.

[Diesel911]

Perhaps the top portion of the Guide Cracked off or the Guide somehow slipped down.

A pic would be extremely interesting.

[barry123400]

The slipping down I could visualise as well as diesel 911 mentions. Since he had the spring removed to attempt the change of the valve seal. He would have noticed a tremendous amount slop if it where not present. Thats if he was using the piston to hold the valve up rather than air pressure.

Normally if the guide is found loose it is still in it's relative position. A loose guide is not really that uncommon with these heads. This would be the first instance of actaully slipping down I have ever heard of on site if that proves the case.

[t walgamuth]

I was thinking it must be shorter than normal. Could the engine run properly with a totally missing guide?

I would think you would get some pretty funny things happenig in a valve cover open to manifold conditions.

[Diesel911]

Originally Posted by t walgamuth

I was thinking it must be shorter than normal. Could the engine run properly with a totally missing guide?

I would think you would get some pretty funny things happenig in a valve cover open to manifold conditions.

The OD of the Valve Stem and the OD of the Valve Guide are too much different for the Engine to run with out something acting as a Valve Guide.
(Of couse a lot of Gaoline Engines have the Valve Guides cast into the Cylinder Head.)

In the Pic below I believe it is possible for the Valve Guide Slip down as there is room between the Yellow lines for that; and, for the Valve to still function.

For it to have a shorter Valve Guide someone would have had to do that on purpose; unless it cracked and someone removed the cracked off portion.

[soulbandaid]

So i pulled the bearing and wiped all the oil off and look what i found.
Its a valve guide.

Since the valve goes all the way up this couldn't possibly be the stock Mercedes guide that migrated too far down (they are also thicker on top near the ring for the valve stem seals to click onto anyway).

The previous owner mentioned that the engine had been rebuilt. I thought he was full of **** cause all of the seals are bad (if you were rebuilding the engine why wouldn't you replace all the seals?) Maybe he had this valve done by someone who didn't use Mercedes guides.

Here's my question. Is there anyway I can seal this so i quit putting out a white cloud of smoke every time i start it?




.

[Diesel911]

It would have been nice to have the pic to begin with. I blew up the pic a little and it and from what I can see it looks like the top cracked off.

Right off I cannnot think of a way to seal it as from the looks of it it; it sits in a little bathtub of Oil.

[t walgamuth]

Originally Posted by Diesel911

It would have been nice to have the pic to begin with. I blew up the pic a little and it and from what I can see it looks like the top cracked off.

Right off I cannnot think of a way to seal it as from the looks of it it; it sits in a little bathtub of Oil.

Yes, I was gonna say the valve guides have a shoulder which should prevent it sliding down into the intake.

I imagine the (doltish) mechanic who installed it broke it off by driving it in too far.

[soulbandaid]

Originally Posted by t walgamuth

Yes, I was gonna say the valve guides have a shoulder which should prevent it sliding down into the intake.

I imagine the (doltish) mechanic who installed it broke it off by driving it in too far.

It's not broken off. Look at the picture. its shiny clean. Whoever f'ed this one up had the head off to do so. The guide is not in too far, the valve comes all the way up.
The bad mechanic work I've seen consisted of a door handle installed wrong. A trunk lock hacked together(since the power locks couldn't work without the door handle!!!)The mechanic who couldn't figure out a door handle couldn't possible get the head off and back on again and then have the car start up. Doesn't putting one of those valve guides in involve heating something?
I really wonder about this...

[t walgamuth]

Not that I have seen. My favorite machinist just takes a special drift and drives them in with a big hammer. I don't really know how it happened but I think you can probably drive with it that way for a while. It will smoke and there is no way around that but it probably will not cause a catastrophic failure immediately. Others can chime in. This is pure speculation on my part. I have never seen such a thing before.

[soulbandaid]

Originally Posted by t walgamuth

It will smoke and there is no way around that but it probably will not cause a catastrophic failure immediately.

Well i'm glad i'm not the only one that feels that way . It drives nice except for the smoking on start thing. But i'd do a lot of things to lower my oil consumption before i pulled the head and sent it off to a machine shop (turbo drain pipe anyone?). Come to think of it i spent about 1000 on this car with the intention of driving it till it kicked it and i think thats exactly what i'm going to do

Thanks for all the insight guys.

[soulbandaid]

Originally Posted by t walgamuth

Not that I have seen. My favorite machinist just takes a special drift and drives them in with a big hammer.

Wouldn't this cause the valve not to close because of the length of the Mercedes valve guides?

[layback40]

To fix it the head will need to come off.
It sounds like the PO was a butcher & you are going to find this sort of thing all over the place on the car.

[mplafleur]

I had the valve guide on my Harley get pushed through the head to the other side once. It wasn't pretty. Maybe this occurred gradually. I don't recall how much room there is on the other side before it hits something.