Replaced Valve Stem Seals - My experience - PeachParts Mercedes-Benz Forum

BIGRED · #1 10-31-2007, 10:42 AM

I decided to do a number of repairs on the wagon, starting with the engine which has less power (than our SD), smokes on start-up and uses about 2 qts of oil between changes. Valve stem seals, turbo rebuild and a look inside the ALDA is what I have planned.

Replacing the valve stem seals was not hard nor scary. I didn't need the car for transportation and so I started out with the idea I would do the amount of work I felt like over a number of days. Because the valve springs were so inexpensive (about $5.00 each for genuine parts) I felt it made sense to change them at the same time.

Removed the following to prepare

1. Pulled Air Cleaner assembly
2. Disconnected throttle linkage
3. Removed glow plugs (planned to replace them)
4. Removed injector fuel lines and injectors (wanted to check things out)
5. Pulled valve cover
6. Removed rocker arms

Replacing the valve stems

1. By having my injectors and glow plugs out, rotating the engine was not an issue.
2. That with the piston positioned properly (you rotate it for each pair of valves per cylinder) , the valve can only drop about 1/4" before making contact with the piston. I confirmed the proper location of the piston by applying reasonable pressure to the top of the valve to feel for contact with the piston. It is simple and obvious. I followed the firing order and used my mental picture of cam lobe locations for intake and exhaust from #1 for all cylinders. In my case I had more than one torn up seal with parts at varying locations on the valve stem.
3. loosening the adjusting nut, the valve spring in almost all cases is easy to lift off. Those that might have been trapped, either were wiggled around or I rotated them until they were free. Once the spring was off, I lifted the valve to a fully closed position, to see if the seal was snug. (for the ones that were not torn) and almost all of them allowed the valve to slide back to the point that the valve was resting on the piston.
4. Using a large flat blade screwdriver I worked the old seals off.
5. Cleaned up the area.
6. Lubed the new seal (Green for Exhaust and Black for intake which is counter intuitive at least to me).
7. Pushed them on with finger pressure.

For the following I used a 2" wide, 1/8" thick, pry-bar/nail puller with a rag wrapped around it, a thick washer with a hole large enough to slide over the valve stem (without slop) and a 1/2" drive socket.

8. I slid the washer over the stem and let it rest on the seal.
9. Slid the socket over the stem to rest on the washer,
10. Wiggled pry-bar between the socket and the camshaft, using the camshaft to "pry against".
11. Gently apply pressure while watching the seal to insure there was movement. The seal will bottom out in the intended position and if continue to increase the pressure you can force it past the intended stop point.
12. Replace spring by pressing down with a no marring tool and hand spin on the nut.
13. Replace rocker arms, adjust valves and re-assemble 1 through 6 above.
14. Breath and take your time.

Don

pawoSD · #2 10-31-2007, 11:56 AM

How did the engine run afterwards? Any power/smoke output difference?

I've wondered if my engine needs this done, as it smokes quite a bit on startup...and also uses about 2qts per 4500 miles or so. Hmmmm...

I don't have a spare car to drive though, so if I messed something up, I'm in trouble....thats the dillema.

Anyone else done this with good results?

BIGRED · #3 10-31-2007, 12:15 PM

Still working on getting it back together (polishing valve cover, replacing starter etc), so no feedback on the result of the work....... yet.

I would guess if you had the parts and started on Friday eve, you would be done sometime on Saturday. It depends on your skill, experience, caution, tools available and the speed of your work.

If I had to guess, I think it could be done in the 6 to 8 hour range.

Don

BIGRED · #4 11-15-2007, 05:09 PM

All back together...
During the job, I found several seals torn up and going up and down with the valve movement (doing nothing). I am guessing my oil use will drop if not disappear.

Jeremy5848 · #5 11-15-2007, 05:34 PM

Please update this thread with oil-useage results in a month or two.

Anyone ever do this job on a 603 engine? I have a similar smoke + oil useage problem. My mechanic says it takes "special tools" that he doesn't have and can't find any one to borrow from.

Jeremy

psfred · #6 11-15-2007, 11:44 PM

The 603 will be a pain -- cam has to come out, so rotating the engine isn't possible (well, it is, but you don't want to do it). You must have some way to hold the valves up (compressed air via the injector or GP hole), and a special spring compressor that will reach down into the hole the spring sits in to release the retainer.

I suspect I have the same problem on my "new" 87 300D -- too much blowby and a quart of oil in 2000 miles or so. I have a new head for the "old" one that I never got in -- supposed to have been rebuilt, but the valves had so much clearance in the guides they rattled, no way I was gonna put THAT head on without a rebuild, and some idiot ran a traffic light and totaled the car before I got the head done. May end up pulling the old engine and putting a properly done head on it anyway, as it had NO blowby in normal use - no vapor out the filler cap at idle, and left a quarter sized oil spot on a rag if I pulled the line and wrapped it in 100 miles.

However, oil smoke, especially if you get quite a bit under hard acceleration, is equally likely to be a bad turbo -- oil comes out the shaft seal when it turns (it won't be spinning much except under hard acceleration if the bearings are bad) and burns in the exhaust.

Check be removing the intake hose from the air filter box, then turn the compressor wheel by hand (engine OFF, please, it will eat your hand otherwise). A slight amount of side play is acceptable (just enough to barely feel, 0.010" or so), but any axial play or roughness or tight spots in rotation, you need a new turbo.

Check for excess blowby by pulling the hose from the valve cover out of the air intake hose -- if more than a small amount of vapor comes out with the engine running, you have worn out valve guides or lower end wear problems.

Peter

Jeremy5848 · #7 11-17-2007, 03:20 AM

Turbo is new compliments of the trap oxidizer recall, performed earlier this year (none of the POs had it done). The turbo was damaged and so was replaced free along with a complete new exhaust system.

Blow-by does not seem excessive. Mechanic and I do not suspect rings or valve guides as compression is good -- engine starts easily, even without pre-glow, and idles smoothly.

You confirm what my mechanic says -- seal replacement is not easy.

Jeremy

t walgamuth · #8 11-17-2007, 06:21 AM

I don't see how valve issues of any kind can cause blowby. blowby can only logically be caused by bottom end issues, imho.

Tom W

Jeremy5848 · #9 11-17-2007, 11:10 AM

Congrats on your 12,000th post, Tom!

My mechanic said that badly worn valve guides could cause a valve to shift its position and not seal properly, thus allowing combustion gases to leak into the area under the valve cover.

Jeremy

Scott98 · #10 11-17-2007, 12:59 PM

Quote:

Originally Posted by Jeremy5848

Congrats on your 12,000th post, Tom!

My mechanic said that badly worn valve guides could cause a valve to shift its position and not seal properly, thus allowing combustion gases to leak into the area under the valve cover.

Jeremy

If your guides were that bad that would need to be replaced immediately before your valve breaks off.

I just replaced the valve stem seals in my 911. It was a royal PIA compared to what I've read in this thread. Are you saying you don't need any spring compressors? What's the tightening torque on the rocker shaft bolts? I might actually try it on my 240 because it consumes oil between changes though it really doesn't smoke on start up so I don't know if it will be worth it.

Scott

whunter · #11 06-14-2008, 09:19 PM

Quote:

Originally Posted by t walgamuth

I don't see how valve issues of any kind can cause blow-by. blow-by can only logically be caused by bottom end issues, IMHO.

Tom W

The OM617 Turbo builds "pressure" inside the intake manifold = bad valve guides and/or seals allow additional pressure into the valve cover/crankcase.

OM617 blows exhaust gasses/plasma "pressure" out to spin the turbo up to speed = higher pressure in the exhaust manifold will seek any escape = bad valve guides and/or seals allow additional pressure into the valve cover/crankcase.

Note:
I had a demonstration head from an OM617 at the January 26, 08 Cold weather Diesel Tech Session ++ Detroit event.
The best valve guide in the cylinder head showed 0.11429 MM slop, can't find the spec at this moment, however that is way beyond junk.

If a valve can be moved sideways in the guide at all, that guide is junk.....

On a turbo you go from neutral to a lot of positive pressure in the manifold. With the rocker cover off, you can manually rev it up to create boost pressure, and sometimes see oil blowing up away from the valve seals = positive proof of a bad valve guide.

Scott98 · #12 06-15-2008, 10:47 AM

Quote:

Originally Posted by whunter

If a valve can be moved sideways in the guide at all, that guide is junk.....

I wouldn't go quite that far. I've seen a brand new valve guide with the valve inserted and there is the tiniest bit of play. The only way to be certain is to measure the lateral movement of the top of the valve stem and see if it is within spec for your engine. I agree, the amount of movement is very, very minimal, but it is detectable. If you don't have anything to measure it with, you can always do a comparison with all of the other valve guides in the engine - seeing if some are clearly more worn than others. Chances are your exhaust valve guides will have the most wear. Be sure to push the valve in some and try to wiggle it to get a good idea of how much wear you are dealing with. Just my thoughts.

Scott

Diesel911 · #13 06-15-2008, 06:37 PM

Quote:

Originally Posted by Scott98

If your guides were that bad that would need to be replaced immediately before your valve breaks off.

I just replaced the valve stem seals in my 911. It was a royal PIA compared to what I've read in this thread. Are you saying you don't need any spring compressors? What's the tightening torque on the rocker shaft bolts? I might actually try it on my 240 because it consumes oil between changes though it really doesn't smoke on start up so I don't know if it will be worth it.

Scott

UPDATE: The site below is no longer there.

The spec you need will be somewhere in here; Pick your engine:
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/Main.html
You can compare the valve stem changing proceedure to the 911 that you completed.

lee polowczuk · #14 06-15-2008, 06:52 PM

i have a 103 gasser...but i was going through oil at a quart every 300 miles at 210k on the engine.

did the valve stem seals about 4 months ago... i now go through a quart somewhere between 1500-1600 miles... i am very happy.

the engine now has 220k. I am sure it will be good for another 30-40k.

i am sure there are some valve guide issues at this mileage..but the car doesn't owe me anything.

actually i had bought it as a spare, but when gas started going throught the roof, i parked an suv.

erik1 · #15 09-06-2008, 03:31 PM

Quote:

Originally Posted by Scott98

I wouldn't go quite that far. I've seen a brand new valve guide with the valve inserted and there is the tiniest bit of play. The only way to be certain is to measure the lateral movement of the top of the valve stem and see if it is within spec for your engine. I agree, the amount of movement is very, very minimal, but it is detectable. If you don't have anything to measure it with, you can always do a comparison with all of the other valve guides in the engine - seeing if some are clearly more worn than others. Chances are your exhaust valve guides will have the most wear. Be sure to push the valve in some and try to wiggle it to get a good idea of how much wear you are dealing with. Just my thoughts.

Scott

Scott, Do I need special spring compressing tools for removing and putting back the springs? How do I re/re the springs? Thanks