What is this thing that is leaking oil? - PeachParts Mercedes-Benz Forum

Bob Albrecht · #1 05-01-2011, 05:56 PM

I'm tracking down oil leaks.

The thing in the attached picture is leaking plenty of oil, but I don't know what it is.

What is it?

I want to order the parts to fix it.

Chas H · #2 05-01-2011, 05:59 PM

Looks like the chain tensioner. But that shouldn't leak if the cap is tight.
Looks more like the front seal is leaking.

86-300sdl · #3 05-01-2011, 06:01 PM

That's the timing chain tensioner. Give it a slight turn either way and maybe it will stop leaking. Or order a new seal if not to many miles on the tensioner.

86-300sdl · #4 05-01-2011, 06:07 PM

Based on the spray pattern (wet areas) in the photo you may also or only have a Vacuum Pump Gasket leak. Do you have oil spray on the A/C unit too?

Just fixed mine and it cleared up multiple "possible" sources I was thinking had to be fixed. A leak at the vacuum pump gets blown all over. At least on a 603 motor. Is that the motor you have?

Bob Albrecht · #5 05-01-2011, 06:28 PM

This is a 603.

It is leaking from the end of the chain tensioner, I don't see any oil on the other side of the engine.

What is involved with chaging the seals on the chain tensioner?

Bob Albrecht · #6 05-01-2011, 06:30 PM

How many is too many miles on the chain tensioner?

The engine has 120K on it. 70K since rebuild, but I dont' know if the tensioner was changed/

Jeremy5848 · #7 05-01-2011, 07:04 PM

100K miles is probably a good number. The springs can weaken over time but I suspect dirty oil is the major cause of chain tensioner failure. If you keep your oil clean the tensioner should last longer but it's not an expensive part and is easy to change. Like many Mercedes parts, the chain tensioner has an aluminum seal ring that needs to be changed; new parts typically come with a new seal ring.

OTOH, I just changed my chain tensioner as part of changing the head on my OM603 engine. The new tensioner (no-name brand, bought from an on-line supplier) had a hole in the end where none is supposed to be. It leaked oil so I put the old one back and am in the process of requesting an RMA number for the purchased tensioner.

Here is the leaky new tensioner. Looks like the machinist got a little overenthusiastic with the drill press:

Here is the old tensioner, Febi brand:

Here is the FSM diagram of what's inside:

Jeremy

Bob Albrecht · #8 05-01-2011, 07:36 PM

The oil has been changed every 3000 miles, without fail.

I will get another tensioner.

Is there any trick to installing it?

Jeremy5848 · #9 05-01-2011, 08:12 PM

Engine off and cool/cold (so you don't burn yourself). Key in pocket. Standard right-hand thread. Break the torque of the old one with a 32 mm socket and a long breaker bar. Tensioner should then unscrew by hand.

New tensioner must be pre-filled with oil. Stand the tensioner in a cup of oil. There's a hole in the case at the end of the threads (where the seal ring lives). This hole must be in the oil. Use something like a drill press to push on the tensioner so that the plunger on the inside end is forced into the body. With no oil in the tensioner you can easily push the plunger in by hand; once oil fills the air spaces it will become "firmer." Use smooth, slow strokes 5-10 times to get all of the air bubbles out.

Now screw the new tensioner into the chain case, making sure the sealing surfaces are clean and you don't cross-thread the steel tensioner into the aluminum timing case. Screw the tensioner all the way in; the plunger should go smoothly into a matching hole in the tensioner arm but you have to work by feel. Once the tensioner is all the way in, torque it to 65 NM (about 50 ft-lbs).

Any Albrecht relatives in Lindstrom, MN?

Jeremy

Bob Albrecht · #10 05-01-2011, 08:27 PM

Thanks a lot for the tensioner installation info.

I suppose I am going to have to buy a big socket that I won't use anywhere else.

One can't be too careful when threading stuff into aluminum.

I don't think I have any relatives in Lindstrom, MN, but it sounds like the kind of place where one would find an Albrecht. I am from Seattle, and my parents live there, and my father is from Cleavland. My sister lives in Anchorage, AK.

After arresting me, the police told me that there is another person with my exact name and birthday / year who lives outside Chicago who has a long criminal record. Fortunately they have a different SSN. They apologized for their mistake, but it was not fun.

Bob Albrecht · #11 05-03-2011, 02:34 PM

I finished the job just now.

The new timing chain tensioner (Laso) appeared to be already full of oil. It was very hard to depress and it went very slowly. I depressed it 5 times in an 10-W40 oil bath and the resistance was the same each time. It was packed in a small ziplock bag and the whole unit was quite oily as-is.

The old timing chain tensioner had some spring left in it, but was relatively easy to depress. There was no shock-absorbing character to it at all. I put it in an oil bath and tried it with the same results.

I did have to buy a 32mm socket for the job.