Timing chain problem? 1998 C230 - PeachParts Mercedes-Benz Forum

mpolli · #1 05-17-2017, 07:12 PM

Hello,

Car is the one in my sig, 1998 C230, W202, 4 cyl M111 engine.

It is making a new noise from the top front of the engine that occurs about once per second at idle. Doing some rough math I am thinking that is about how often the timing chain would go one complete pass at idle speed.

Am I in imminent danger? Is there an easy-ish way to inspect for the trouble?

Thanks

97 SL320 · #2 05-18-2017, 05:29 PM

Pull the drive belt and see if the noise goes away.

These motors do have timing chain wear issues, do you get more noise at start up before oil pressure builds?

I'd at least pull the valve cover and have a look.

mpolli · #3 05-18-2017, 08:53 PM

I will try pulling off the belt but the noise seemed to be very distinctly coming from under the valve cover, right above the timing chain. I have ordered a chain replacement kit with tensioner and rails but I am having a hard time finding much info on the procedure. My Haynes manual only has a chain-only procedure, or a complete cam sprocket chain, everything procedure. I am wondering if I have to remove the timing cover to do the rails.

mpolli · #4 05-19-2017, 01:00 AM

I pulled the belt off and it made no difference. That makes sense since the belt goes around much faster than the chain due to the larger crank pulley size vs crank sprocket. I tried pulling off the valve cover and got all the way done except could not get the cover unglued. Mine is in great shape with no paint chips so I didn't want to pry it but I don't see how to get it unglued. Anyone know how to do it?

jake12tech · #5 05-19-2017, 01:37 AM

About 90% sure you have to take off the timing cover to do the rails. Every MB I've done had to have the cover removed. At your mileage, I'd wager 40/50 chance it's your chain. Replace the tensioner as well.

mpolli · #6 05-19-2017, 02:59 AM

How do I get the cam cover off? Just whack it with a rubber mallet?

It looks like to do the rails I have to remove the head, so that won't be happening.

I will do the chain, tensioner and the upper guide block (if that is what it is called)

How do I rivet the chain link?

Thanks

Hirnbeiss · #7 05-19-2017, 08:36 AM

Here's the M110 procedure:

Replacing timing chain

mpolli · #8 05-19-2017, 01:26 PM

Thanks. Does anyone have any ideas on breaking the cam cover loose?

TX76513 · #9 05-19-2017, 04:01 PM

One minute removal
https://www.youtube.com/watch?v=BohubIH0OEs

look to right margin for related video's also.

97 SL320 · #10 05-19-2017, 05:12 PM

Make sure all of the coils and bolts are out. Did you remove the plastic clip on cover in the front of the engine? I think there is a bolt there since it more or less follows M104 inline 6 being it is a cut down 6

mpolli · #11 05-19-2017, 06:11 PM

Quote:

Originally Posted by TX76513

One minute removal
https://www.youtube.com/watch?v=BohubIH0OEs

look to right margin for related video's also.

I don't know what engine that is. It is not a M111 that's for sure.

mpolli · #12 05-19-2017, 06:12 PM

Quote:

Originally Posted by 97 SL320

Did you remove the plastic clip on cover in the front of the engine?

Yes.

I will whack it with a mallet. Can't think of anything else to try.

mpolli · #13 05-21-2017, 12:51 PM

So I'm half way done. Will give a final report when I am (hopefully) done later. What I tried to get the cam cover off:

Hit with rubber mallet: Didn't work
Tried driving wood wedge in the small gap: Gap too small, wood crumbled.
Finally I drove in my thinnest 1-1/2" wide putty knife, at the corner by the dipstick handle (front passenger corner of cam cover). This seemed to have a slight effect. Then I replaced that with a thicker knife/scraper that had a sharp edge. That finally popped it off.

Now for the replacement procedure which I got straight from the Mercedes manual (and Haynes showed the same exact one):

"1. Connect new timing chain (5) to old timing chain (4) using assembly link, consisting of chain joint (6), plate (7) and locking element (8).
2. Pull out locating pins.
3. Slowly rotate crankshaft in direction of rotation of engine.
4. Pull the end of the old timing chain (4) which becomes free evenly out of the chain housing as the new timing chain (5) is drawn in.

Ensure that the timing chain does not jump across as it is tamed"

It is that last part that is the doozy. Keeping the cam sprockets from jumping under valve spring tension is basically impossible. I had a friend helping me, and we are both experienced mechanics, and nothing we tried would make this procedure work well. I am really curious if anyone has actually ever done this. I can find no evidence online of anyone who ever tried it.

Will report back when I am done.

97 SL320 · #14 05-21-2017, 06:59 PM

I haven't done one of these but from a straight repair analysis, I'd let the new chain droop over the exhaust cam then outside the engine, as you roll it in things should be OK. The cams will snap back and forth but I would not expect them to be so far out of time that a valve would hit while slowly turning the crankshaft.

Once the chain is all the way around I'd recheck cam timing before the master link is set.

mpolli · #15 05-27-2017, 04:45 PM

So I want to close out this thread and hopefully help anyone who ever has this issue or tries this repair.

To recap:

Symptom I had: A noise at idle (750 RPM) that was under the front of the cam cover of the engine (where the timing chain is) and occurred around once per second.

I decided (correctly) that the only thing that repeats at that speed at idle is the complete rotation of the timing chain. In fact, the actual repetition rate would be (RPM/60)/(chain teeth/crank sprocket teeth) = (750/60)/(128/16) = 1.56Hz, fairly close to my estimate of 1Hz.

I guessed that there was a defect in the chain caused by wear and it could be in danger of snapping.

It turns out it did in fact have a stiff or seized link that was caused by wear (see picture)

So I tried the procedure mentioned previously and had pretty bad results. I am thinking I was supposed to have one of these:

BGS Tools Timing Chain Mounting Tool For Mercedes M111 8680 | eBay

Even though the Mercedes procedure does not mention it. Alternately if I had to do it again I might try leaving the camshafts unengaged from the chain and just winding the chain through and around the crank. As long as none of the valves are open this might work.

The other horrible thing the Germans did is the chain tensioner. I have no idea what the official way is to get the cap of that screwed on while simultaneously compressing that big spring that is in it. I only found one video on YouTube where a guy actually did it and he did not film what he actually did, but he said it took an hour and was "soul crushing". Those are strong words but I think fair in this case.

This job far exceeded my expectations of the amount of time and work involved.