Where'd my valve guide go? Help pls.
 

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.

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.

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

A pic would be extremely interesting.

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.

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.

Answers and questions
 

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?

http://www.peachparts.com/shopforum/...-pls-valve.jpg


.

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.

I don't think so. It's better than having a guide that slipped down though, probably.

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.

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.

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...

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.

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.

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

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.

See the pic in post #6 there is actually room for it to drop down some.

I think I have figured out a way to change the Valve Guide without removing the Cylinder Head.

But, please remember I am not there to see it and I have not had a Mercedes Cylinder Head off or changed any Valve Guides on a Mercedes.

Remove from the Head what ever parts are needed so that you can get at and remove the Valve springs just as it is in picture in the original post.

Rotate the Engine by hand and let the Valve drop down enough so that you can use a Tap to thread the inside of the Valve Stem Guide.
Use a Slide Hammer and pull out the Valve Stem Guide.

Do what ever is needed to clean out the Valve Stem Guide hole.

Rotate the Engine by hand to TDC so that the Valve is all the way up.

You will need some sort of Tube that will allow you to drive in the new Valve Stem Guild and not mess with the Valve.

Slide the new Valve Stem Guide over the Valve Stem and drive it in.

Put on the new seal and assemble the Head.

Isn't that more or less what i said in the fist post minus the removing the bad one part?
I think you would probably lose the valve when you tried to pull the sleeve. There isn't really much clearance between the cam and the valve guide hole. You'd have to get teh vavle way down and even then you'd probably need to pull the cam in order to apply any significant pressure to the new guide. But I've heard people say that one can fish out a valve with a magnet (sounds like almost as much fun as pulling the head :-P)
I also get the feeling that that guide is not a Mercedes one. It's machined flat on top and the valve closes all the way (the car runs well except the oil smoke on start). The mercedes ones are slightly beveled and so long that the valve wouldn't close with it shoved way down in there. I suspect its a machined bronze or brass ring that was put in there with some force (do they do this on other cars?). I wish someone could give me an answer that sat right with me. But I'm the first to admit that I'm an amateur and probably don't know what I'm talking about.

Anyhow doing that and risking making an engine that works with its head onl into one that doesn't work without pulling the head to fix it right (or replace it!:eek:)doesn't really seem worth it when the only issue i have is oil smoke on start and moderate oil consumption in a car I paid 1000 for.

Thanks for all the help and advice.

if you are really upset by the smoke [which you assume is oil] , you could modify a valve stem seal to lay under the 'bearing' or 'rotocap' that sits under the valve spring.

the only thing you can do is wipe the oil off the stem before it reaches the guide.

Another thought is a large rubber washer , maybe viton. Regular black rubber will not last long under those conditions.

I figured that ounce the Old Valve Guide is out there would be plenty of room to "find the Valve"; and a Magnet would work.
I also believey you would need to remove the Camshaft remove and install the Vlave Guide.

This is going to be hard to describe.

You take a shortened piece of a Valve Guide; the part with the lip that holds the Valve Stem Seal on; you would have to figure the length.

you Braze that piece of Valve Guide to the thin washer (the washer needs to be like sheetmetal thin so the Valve Springs sitting on top of the washer do not become coil bound) about the outside diameter of the hole that the Valve Springs goes in.

When you install it you put a coating of Silicone Sealant on the Bottom of the washer and slide it over the Valve Stem. Followed by the Valve Stem Seal.

The Valve Spring will sit on the top of the Washer pushing it down and the Silicone will prevent Oil from getting under the Washer. Since the section of Valve Guide is Brazed to the Washer it will not leak there.

The Valve Stem Seal should seal the Valve Stem itself.

The main rub is that the new Brazed on section of Valve Guide is going to have a tigher ID than the old piece of Valve Guide that is still in the Head; so there would be some side ways force exerted on it when the Valve goes up and down.
It would work best if the hole in the Brazed on section of Valve guide was enlarged so it would not touch the Valve Stem so no sideways force could break it off at the Brazed joint.

Might be easier to pull the Pre-Chamber, bang the valve-guide out into cylinder, and fish it out with a Magnet on a stick!

--All depends on whether the Valve will drop outta the guide with the Piston at BDC--If it wont, then this idea wont work....

Driving in the new guide after the old is out is easy, and getting valve back up isnt hard with long-nose through manifold tract in head after you have the manifolds off....

Problem may be that with the New Guide fitted, the Valve wont seal properly without re-lapping/facing it in, as it may not be in Exactly the Same position as the Old, Worn guide,--With the small side-force on the valve-stem imparted by the follower, the valve seat after a few hundred K miles wears slightly eccentric.....:rolleyes:

I agree with Alastair, except that pulling the prechamber will not help you remove the valve guide, really.

and that guides usually need a good reaming before the valve slides easily.


you cannot (properly) install a new valve guide without removing the head.

work with what you have.

You know I had the same exact thought after I put the valve cover back on. The oil smoke bugs me, mostly because i want to sell the car and it looks tacky when a cloud of smoke comes out as you start it:o. Oh well, after spending three days with it apart (i work slow cause its hot here) and stripping the oil filter lid stud )DOH(. I'm not all that motivated to take the vavle cover/valve spring off again.

honestly,

it probably is not worth your time. The whole point of having the valve stem rise above the rotocap is because that area fills with oil.

Having a valve guide cut off flush with that surface severely limits your options to making an effective seal... ever... without removing the head.

actually, post #22 by D911 is the only fix worth trying.

it is rife with potential failures and you will need some very precise work done... but it is the quickest / least invasive solution.

Recycled
 

for new owner.

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Link to the same discovery
 

Check this posting out...specifically post #53 on page 4. I found the exact same thing. White smoke and all. The seat was wallowed out pretty good and needed a full valve job. I think we drove this car for a long time like this, maybe even since we got it until the headgasket let oil into the coolant. The car ran good, up to that point.
http://www.peachparts.com/shopforum/diesel-discussion/312485-85-300td-blown-headgasket-4.html

And here I was thinking I was unique....seems the broken guide is not uncommon. I sure wish Roy lived near North Carolina though, even having done it once now I believe I'd still rather hire a pro to do that job.... Although I'm planning on a full 617 rebuild just because I'm crazy....and Stretch needs competition from this side of the pond.

Yea stretch is the man to consult for the finer details. I just got through reading some of this thread:

http://www.peachparts.com/shopforum/diesel-discussion/276144-om617-manifold-oil-%3D-broken-valve-guide.html

Best check this one out when you do this job. After reading this thread I found myself asking myself these questions....Why did'nt I check to make sure the valve springs were installed correctly?....and would valve lapping be considered something I should have expected the machinist to do when he rebuilt my cyl. head last summer? He did charge me for a complete valve job....and I did'nt do it...d-oh

In hindsight I really wished I had access to that thread at the time. I have also wondered if I should be consulting Stretch for everything from now on....man, that guy pays attention to the small details. Forgive me for saying that Stretch should have his own site, for all the documentation he has done here. That in itself is alot of work. If I have'nt mentioned it before, Thanks, Stretch for all your contributions to this site...and everyone else for that matter. Stretch seems to stretch the extra bit on the details...I appreciate it. He is valuable part of this site, and he takes awesome pictures. Roy too, He has always been here and sometimes gets left out and taken for granted cause thats what happens to old faithful. He's gone to great lengths to be there for some of us including taking personal phone calls, wow.

Without guys like these, to offer (free) their knowledge, some of us could'nt afford to own one of these vehicles. They go above and beyond, and are inspiration. Oh new thread idea.