Here I go Again

[Rolf]

I had a thread and called it "Miss Firing" The problem was the number 6 intake valve lost its keepers. I replaced all and checked for loss valve guides, bent valve stem, damage in the valve stem groove, etc. I replaced the keepers, retaining ring and shim. Now after going about 400 miles, the exact same thing happened. The keepers were gone from the groove and the valve dropped. (Number 6 intakes again) I contacted a Mercedes mechanic, who does work on the pagoda's, and was told to make sure the rocker arm is riding on the valve stem and not the retaining ring to insure the keepers have positive pressure against so as not to loosen up. He cannot figure out why the keepers would come loose except for that situation. All the other valves are fine. Any thoughts as to why this is happening or how can one check to make sure the rocker arm is riding on the valve stem and not the retaining ring?

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[ja17]

Hello Rolf,

Good advice by your mechanic. This can happen if you have a thin valve contact shim in place.  You can manually grind the undercut of the rocker arm to gain more clearance for the retainer.

Did you do any other danage this time?





Joe Alexander
Blacklick, Ohio

[Rolf]

Hiyas Joe,

  No damage this time. I shut the engine off as soon as I noticed something wrong. The main problem was, it happened about 130 miles from home. Are you saying to grind down the underside of the rocker arm to obtain more clearance over the retaining ring? Will that weaken the arm? The shim part is the one with the "ears" that the rocker arm rests on? If so, it is a new one from Mercedes.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[ja17]

Hello Rolf,
If this is the problem you will see a rub mark on the underside of the rocker where it passes over the retainer ring.  Yes, the shim pads have the two ears. They come in different thicknesses. Normally, only the very thin ones ever cause a problem like this. Using a thicker shim pad will often cure the situation, but if you cannot get enough valve adjustment you will need a thinner one and may have to grind the rocker arm as discussed.

You can grind the rockers quite a bit with no problems. The area to grind is a non-machined rough part of the casting.

Joe Alexander
Blacklick, Ohio

[Rolf]

Hello Joe,

  Thank you. Is there a way to tell if the shim is riding on the valve stem or if it is riding on the retaining ring. I do not know the history of any valve work. I do not know if the shim is riding on the valve stem or the retaining ring. If it is, does that mean new valves or is there a way to shim that up on the valve stem? Can I use blue dye to tell? The shoulder of the retaining ring is shiny but, I don't know if that happened after the keepers came out or before.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[ja17]

Hello,

Normally the shim will be riding on the valve stem with the retainer holding it in place. When there is a clearance issue the shim is  thiner and the machined valve is a bit higher in the head. In this case the rocker arm is in contact with the rim of the retainer instead of the valve stem. When the rocker arm is depressed by the camshaft the retainer is pushed down first loosening the valve keepers instead of pushing down on the valve stem first!

Joe Alexander
Blacklick, Ohio

[Rolf]

Hello Joe,

  Thank you for the info. I took a look at the bottom of the shim  and noticed a circular mark. To me that indicates the shim is riding on the valve stem but I don't know if it hits the valve stem first or the retaining ring. After I get the new parts installed, I plan to put some bluing on the bottom of the shim and rotate it and see if the bluing rubs off where it should contact the valve stem. If it does and I have the problem again, I will have to look elsewhere, I guess. If it rubs off where the shim makes contact with the retaining ring, then I know what has to be done.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[ja17]

Hello Roff,

Most likely the point of incorrect contact is on the bottom of the rocker arm, where it passes over the retainer . Look for a mark there!

Joe Alexander
Blacklick, Ohio

[Rolf]

Hello Joe,

  I looked for marks or other indications on the rocker arm and the retaining ring and found none. I am just wondering if the valve stem was cut and if so, cut too short. I do not know the history of the motor. I figure, if there were no marks there, that maybe the shim is riding first on the retaining ring instead of the valve stem.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[ja17]

I see Rolf,

I guess this could be possible.

Joe Alexander
Blacklick, Ohio

[Rolf]

Hello Joe,

 I ordered the parts and I will give you an update as soon as I receive them. On another note, I read an article which stated that Blacklick was one of the more desirable places to live. Just thought I'd let you know.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[ja17]

Hello Rolf,

Are you sure it was Blacklick Ohio!

Joe Alexander
Blacklick, Ohio

[rwmastel]

quote:Originally posted by ja17

Are you sure it was Blacklick Ohio!

Rolf lives in New Jersey, so Blacklick is probably great!     Actually, there are some great parts in NJ, so just joking.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[Rolf]

The article mentioned Blacklick, Ohio, along with other places in Ohio. I guess it's all according to what one desires? Besides, NJ is number one in sevearal areas, first in property taxes, first in the cost of auto insurance, first in the number of lawyers per population (one lawyer for every 35 people), highest cost of living, and has the most people per square mile. Oh, I almost forgot, New Jersey has Wolfgang.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[Rolf]

Update time. I finally got the valve parts from Mercedes. New springs, keepers, valve seal, retaining ring and thrust shim. I matched the keepers up with the valve to make sure the valve wasn't an aftermarket one with a different type of groove. The keepers fit like a glove without any movement. I assembled all of the components and double checked everything. I even took the valve spring compressor to the valve, after it was assembled and compressed it more than the rocker arm does to see if any negative thing happend. All was good to go. I checked the valve stem to make sure it did come up above the retaining ring. I don't know if there is any minimum measurement for it but I got .0735 inches above the retaining ring. After finishing, I took the lil darling for a ride and it sounded wonderful. If it happens again, I guess I'll have to remove the head and do a valve job. Something I am not looking forward too. I was seriously thinking of going to Blacklick with the car but I don't want to chance the drive with all that's been happening. I will take drives closer to home in hopes that all is well. Thank you all for your help and suggestions. Have a great time in Blacklick, maybe next year will be my time.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[al_lieffring]

Rolf

I had seen something similar to this before, It turned out to be the top of the valve stems had been ground off so thin that the rocker pad would make contact with the spring cap before it came in contact with the valve stem, I ended up having to grind a 45deg. champher around the bottom of the rocker pad so the pad was pushing against the valve stem without pushing down the spring cap first. If the cap moves first, there is no pressure to hold the keepers in place allowing them to wear prematurely and eventually fall out.



Al Lieffring
66 230Sl
Jones'n for a new gas tank

[Rolf]

Al,

  If it happens again, third time, maybe I'll try that. The second time it happened, I only put around 400 miles on the car. the first time was around 1,500 miles. I know the stem is higher than the retaining ring. I don't know how high is normal though. Did you use a Dremel with a stone? Was the diameter of the thrust cap about the same as the valve stem?  Thank you.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[Rolf]

Here's another update on the infamous number 6 intake valve. I removed the rockers on the number 6 and number 5 intakes for comparison and found the number 6 valve stem has been ground down quite a bit, approx 1/16. To get me thru the good months, I think I am going to go with Al's remedy and put a 45 deg champher on the thrust pad.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[Miss230sl]

I'm sorry you're having so many problems - have you considered starting over on this car or maybe replacing it?

[Rolf]

I haven't thought of replacing the car. It has some issues and I am slowly working them out, with help, lots, from the people on this forum. I have heard about cars in worse shape than mine. The head will come off this winter and new valves will be installed along with the other essentials.It seems the mechanic who worked on this car before I got it didn't know as much as he lead the person to believe. And I am learning about the car as I get it the way it should be. It's a fine car, just needs some loving care.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[al_lieffring]

Rolf i sent a reply to your E mail. Let us know what you find out.

Al

Al Lieffring
66 230Sl
Jones'n for a new gas tank

[Rolf]

Al,

  I ground a 45 deg champher on the cap and put a thin layer of grease on the pad part. Installed the cap and rotated it. I removed the cap, the only place grease was still present in quantity was on the champher. The rocker arm does hit the retaining ring at any point. I hope this "fix" works, at least until the winter months. Thank you Al.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS