Troubleshooting my engine knock (long-ish) 1982 300D - Page 10 - PeachParts Mercedes-Benz Forum

LuckyEddie · #**136** 02-16-2010, 05:34 PM

The clip ring is around the plunger. The tensioner body has grooves in the plunger bore that have an angle on the chain side of the groove and is square cut to the outside As the chain stretches the plunger moves out from oil pressure to take up the slack in the chain. The ring will hold the plunger in place when the pressure is low and when the engine is off. Turning the engine backwards can shear the ring. The ring is worn out at about 200K or less. I have been replacing them in my cars as a service item. I have also been resurfacing the plunger where it contacts the rail.

Later
Robert

konstan · #**137** 02-16-2010, 06:13 PM

Ok I will order and replace the ring. That's a good idea. Dealer only item, I assume?

I ordered the replacement bushing, spacer, bolt and the bronze bush from Phil on this site.

Now all I have to do is decide whether to put it back together, or go for the head. I do have the manifold and the turbo off already... I mean, I know you said put it back together first, but.. are you SURE?

How heavy is the head?

LuckyEddie · #**138** 02-16-2010, 11:19 PM

Quote:

Originally Posted by konstan

Ok I will order and replace the ring. That's a good idea. Dealer only item, I assume?

How heavy is the head?

The ring is less than a dollar. If you have the valve cover off remove the tensioner spring and see if you can push the rail out and that will push the plunger out also. If you can the ring is bad but you will not need to remove the tensioner body just replace the ring otherwise removal of the water neck is necessary.

The tensioner is just another thing to look at for noise at low RPM and they do fail.

The head is heavy and has two allen head screws inside that need to be removed also.

Later
Robert

layback40 · #**139** 02-17-2010, 01:39 AM

The head is heavy enough. 1 person can lift it.
I believe that if its not broke dont try and fix it.
The end float that you have found is likely to cause the knock you heard.
If it was me, I would put the motor back together & see how it runs. If there is still a problem then you may need to look deeper.
Unless you are wanting to just pull it to bits to see how it works, best minimize the dis-assembly.
At the end of the day, you have been very lucky to find the problem remaining from the vac pump bearing before it caused a major failure.

konstan · #**140** 02-17-2010, 02:46 PM

Ok, as the replacement parts are gradually starting to show up, I am going to start putting her back together. We will leave the head for another time.

I will clean the intake manifold, since I already have it off.

I could clean the intake ports on the head, since they are accessible with the manifold off... is that worth doing?

The rocker arm on the 1st valve (cylinder 1 exhaust) seems looser than the others, just noticed that yesterday (yes I did the valve adjustment previously but it was my first time doing it)... if I get a finger under it and lift it, I can hear an audible click against the cam lobe... that leads me to believe it has too much travel or its loose or something...

barry123400 · #**141** 02-17-2010, 05:41 PM

Check around that valve carefully for a broken valve spring or something. It is very strange to find a loose clearance in the area the mechanic suggested the noise was in.

Especially if you do not feel you did the valve adjustment wrong so short a time ago. Could the piston have been tapping the valve back up for example? Try to see if you can pull or pry that valve higher to reduce the clearance you feel. Do not be too aggressive though.

Or press the valve down and see if it is returning properly as well. Of course the engine will have to be off top dead centre for that. It will probably have to wait until the item you are working on now is completed. I only assume you put the engine at top dead centre before you started.

konstan · #**142** 02-17-2010, 07:53 PM

Quote:

Originally Posted by barry123400

I only assume you put the engine at top dead centre before you started.

Its in the "line up the camshaft mark yada yada yada..." position right now.

barry123400 · #**143** 02-17-2010, 11:24 PM

I only immediatly targeted this because you strike me as an individual that would not screw up a valve adjustment normally. Even if it was the first time you did it. This could be the answer to the rough idle as well.

Piston assisted valve closure that is. Probably not but worth checking out. Your foreign car mechanic might be able to verify or reject the concept as he heard it. I think you may have gotten his curiosity up so he may reflect upon it if asked.

You thought you felt something when turning the engine over as well. After all there is not much that high in the engine to make a noise. You would hear a piston hitting a valve though when the engine was running. Just a long shot but easy to check.

konstan · #**144** 02-17-2010, 11:48 PM

Quote:

Originally Posted by barry123400

I only immediatly targeted this because you strike me as an individual that would not screw up a valve adjustment normally. Even if it was the first time you did it.

Stranger things have happened.

For example (this is slight off-topic). I bought this old Ford Explorer for $600 bucks. It needed the front end ball joints, tie rod ends, etc. and some general TLC.

Then I was having this terrible backfire problem with it. It was driving me nuts. Eventually the problem turned out to be that I had the spark plug wires hooked up wrong -- two of them were switched over. Yes, I just admitted it! This was my favorite kind of resolution!!!

There is one reason and one reason only why I have not put the 300D back together yet, and that reason is -- I have not found a 'smoking gun' yet, as far as the knock is concerned. You know, the "geez, these wires go the wrong way" kind of smoking gun.

Yea the intermediate shaft that the TD rides on has some play, but, let's be honest -- in 99% of 300Ds out there it is probably like that or worse, and mine was knocking WITH THE VAC PUMP off.

I think taking it to a mechanic was a mistake. Unless the mechanic is a personal friend or relative, their formula is simple: how much money can he make. If he couldn't figure out what is wrong with it in 10 minutes, he wasn't going to figure it out at all.

For when I do put the 300D back together I got some 15W50 mystic oil... or should I go with something ligher, for knock's sake?

barry123400 · #**145** 02-18-2010, 12:16 AM

These engines develop the strangest noises sometimes and self heal. I have never experienced that with another brand. Do not be too sure the mechanic was not sure. Good mechanics seem to operate on instinct a lot. If he said it was high in that cylinder he probably was right.

This may still turn out to be a strange one. I do agree there has been no smoking gun particularily so far. Except the poor idle at low rpms.

I just listened to you idle. It does not sound ragged enough to have a valve closure problem. Also it did well on a compression test. Maybe check the front cam tower for any cracks around the base or loose mounting bolts. At this stage I do not have any ideals . The noise seems fairly loud I agree. I wonder if anyone thinks it might be a wristpin. All I am doing is wild guessing.Since that is pointless. I will just keep an eye on the thread.

konstan · #**146** 02-18-2010, 12:31 AM

Its all new to me too.

Last summer I decided I had to have a diesel mercedes, so I drove to Kansas City (4 hrs away) and trailered one back.

I would've thought this engine is a gonner, but I had it on the interstate at 80mph. It has amazing power, very quick takeoff, I think I would've put a rod through the motor's side a long time ago if low end was an issue...

I'll just keep plugging at it, posting pictures once in a while.

The next excitement is gonna be when the replacement TD bushings show up. Can't wait to measure them to see what has changed and how much mine were worn out...

konstan · #**147** 02-19-2010, 11:52 PM

Update for today:

Took out the oil pressure relief valve bolt, plunger, etc. to make sure there are no debris stuck there. None, really nice and only, no particles.

Got the retaining ring from the dealer for the timing chain tensioner.

LuckyEddie · #**148** 02-20-2010, 10:19 AM

[
Got the retaining ring from the dealer for the timing chain tensioner.
[/QUOTE]

What did they charge for it and do you have a part number??

Thanks
Robert

konstan · #**149** 02-21-2010, 10:45 PM

Quote:

Originally Posted by LuckyEddie

What did they charge for it and do you have a part number??

103 052 01 93

They charged me about $5.50 for it...

konstan · #**150** 02-22-2010, 05:15 PM

A neighbor at the farm came over yesterday and after hearing about the symptoms, the low pressure at idle, etc. said to just yank the motor, tear it apart and figure it out and not to beat around the bush. He suspects a wrist pin.

With that new HF hoist in my garage just looking for work, I will be starting a new thread and post the progress there.