Howdy Folks,

This weekend, at close to 100k mi, I decided to do an easy timing chain replacement (preventative maintenance) on my super-trusty '85 190E. This was due to the parts for the job being given me as a birthday present so that I would have less maintenance woes when I quit my job and become a full-time (read as poor) law student this fall.
So, the job was quite simple...right?
Remove plugs, air cover, serpentine belt, valve cover, tensioner.
BY the way, the head on this car looked beautiful and clean and I was seriously doubting whether or not to worry about using the new gasket that came in the kit.
The chain kit I had also came with the plastic rails, but I was not about to pull the front of the motor off, unless I had to.
The rails looked good, the chain had some stretch, so dad (the retired/former ASE mechanic) and I ground off the link, attached the new chain, and started cranking her through.
After three links through, slack from nowhere came out of the back end of the old chain and we dropped her one or two teeth out of time. We stopped where we were and checked to see that the chain was still coming off and we backed her out maybe three links just to get a better hold on the assembly.
SO, proceeding onward and knowing we were going to have to break out the timing light...we continued to turn the crankshaft...for four inches of chain and she stopped cold. Now, the crankshaft will rotate four inches forward and four inches backward (inches of chain length). That is it. So, we marked our spot, marked the position on the cam and disconnected the chain from the top. The cam turns like a champ. What the heck did we do and what the heck am I going to do now? I have put all the parts back in (new tensioner, new belt, new gasket) and finger tightened everything.

Oh, and Donnie...maybe I should have waited till Spring or called you last week at MBS and driven her up there, when I would have gotten there just fine...now, a flatbed would be calling. *SIGH*

Any clues? Is the front of the motor going to have to come off? Do I really have to take the engine out to get to the timing chain case? Is this now suddenly a decent time to use the plastic guides I had not planned on installing?

My weekend could have been worse, I suppose.

Thanks.


------------------
John J. Meadows
'83 300D 3.0L 260k mi.
'85 190E 2.3L 99k mi.

Well, there aren't too many things that should stop the crank from turning, but..., if you lost the relationship between the crank and cam, the only big item that comes to mind is a piston bumping up against a valve that's open. Nothing else makes any sense to me. At any rate, you will have to get the crank and cam back in synch. There is a mark on the front cam journal cap that lines up with the timing mark on the cam. That should be TDC for #1 cylinder on the compression stroke. However, other valves are in various stages of opening and closing so you may not be able to get the crank back to TDC for #1 w/o hitting valves as you are now. There are two ways you can go. Remove the crank damper and the front cover and manually install the chain. Remove the cam from the top of the head and then get the new chain around the crank sprocket, hold on to the chain, turn the crank until you are sure #1 is at TDC for compression, then reinstall the cam and realign the timing mark and reinstall the cam sprocket. You may me able to feed the chain around the crank sprocket w/o removing the front cover if you are lucky, but at any rate you will have to get all of the valves out of the way and that means cam off valves closed.

------------------
Jeff Lawrence
1987 300e
1989 300e
1987 BMW 325

I would suggest that you remove the rocker stands so that the valves will stay closed. If this allows the engine to turn turn it till the crank is right and then remove the cam gear and set the cam right and install the chain.

Be sure you understand the chain tentioner operation before you reinstall it. Hopefully the distributor drive gear will have stayed in time. Check it after you get the cam straightened out.

All the mechanics are correct.When you turn the engine at the crankshaft bolt to rotate the new chain,the camshaft is not turning. Therefore the pistons will hit a valve that is open and this will lock up the engine. Just take a socket wrench and turn the camshaft as you turn the crankshaft. You will not need to remove the camshaft. This should be a fairly simple job if you are only replacing the chain.If you are replacing the chain rails and guides. Well, thats a lot more complicated and difficult job. They will only need replacing if broken or badly worn.You may want to check the chain tensioner and replace it if it needs to be replaced. Have fun! Wm. Lewallen...

Wm, doing it the way you describe is a crap shoot. If the cam and crank are already out of time, he may spend the rest of his life trying to get the chain in place. There is only one relationship that works with TCE setups and both components have to be in synch. Too much risk of inadvertantly damaging a valve or piston crown. KISS principle applys here..

------------------
Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

Hold on. I have seen a tech do this before, and the pistons were not hitting the valves at all!

What happens is the chain, when not tensioned, can fall into the space between the crank gear and the oil pan. I always use a tensioner with a spring and no piston ratchet to prevent this.

I am sure this is what is up. You can wiggle and jiggle and possibly get the chain back up.

------------------
Benzmac:
Donnie Drummonds
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Donnie, correct me if I'm wrong, but he said in his original post that he could get 4 inches of chain to go on and then it stopped. He could also get the same 4 inches back and it stopped again. Could the chain still be jamming if that were the case?

------------------
Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

Have to agree with Benzmac. I am in the process of replacing the chain and rails on a 16V. My front cover and pan are off (due broken rails) and it is easy to observe how the chain could become wedged if tension (both with the tensioner and manually pulling the tail end of the chain simultaneously!) is not maintained. Trust me, you do not want to go through the NIGHTMARE or removing all the brackets and pumps to get the front cover off. All you full time M.B. mechanics have earned my respect. Give it an other go. Mr. T

Thanks for the early replies, guys. Here is where things stand.
We used the new master link to reattach the old chain to see if the chain would move again...and the chain was one link short. So, we wiggled and jiggled and got the chain back up to being its full length. Crankshaft still wont move more than three or four inches of chain, either direction. So now, old chain is attached and still wont turn.

Based on the responses - I am thinking two possible issues:
1. Chain is still boogered (what a great word) at the lower sprocket which is stopping the crank from turning. (ala Donnie, et al)
2. Pistons are coming up and touching the valves. (ala Steve and Jeff)

So, I have two follow-up questions:
- If I drop the oil pan, will I be able to see the bottom of the chain and how it is connected and if it is ok?
- If the pistons are touching, why does the cam turn freely when I remove the chain and just crank it with its side bolt. If turning the crank made the pistons hit valves...wouldn't turning the camshaft make those valves hit the pistons, too?

At most, she was dropped two teeth out of sync between cam and crank.

Thanks for all the help thus far...

- John

------------------
John J. Meadows
'83 300D 3.0L 260k mi.
'85 190E 2.3L 99k mi.

This thought comes to mind. If you can get the chain back up, just secure it. With the mechanical advantage the cam and valve setup has, it is likely that rotrating the cam is in fact opening the valves and the valve is pushing the piston down. However, you will never be able to push a valve closed with the top of a piston, so rotating the cam leads you to believe that's not the problem. Lets simplify this situation. Don't drop the pan. Do what Steve suggested, remove the rocker stands. This will disable the valve train and all valves will remain shut. Get a good purchase on that chain and see if you can get it to come around. If you say you've got all of it out then the only other thing could be piston valve contact. See if you can get 360 degrees of crank rotation. If you can, get #1 at TDC for compression and get the cam back in synch with the crank. You really only have two possible scenarios, Donnie's and the one Steve and I described.

------------------
Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

Newest Update:

Rocker arms loosened...crankshaft now turns like a champ. Now, just to get cam and crank both set to TDC and see if the ignition timing dropped anything. I home home-timing this thing isnt too much of a pain...if I have to.

So, looks like the resolution of the chain involved both Donnie's and Steve/Jeff's suggestions. First, the chain was caught and secondly, the pistons were also touching the valves due to dropping a few teeth out of time.

I will keep yall posted - thanks for all the help, guys. Oh, and Donnie...I'm still saving the valve job on this car for you for the late Spring. :)

- John

------------------
John J. Meadows
'83 300D 3.0L 260k mi.
'85 190E 2.3L 99k mi.

All right guys, situation is almost resolved. One last question. The MB manual states 20Nm for the tightening torque on the rocker arm bolts. 15 ft-lbs??? This seems like waaaay too little torque to put on those, and frankly, they had closer to 45ft-lbs (60Nm) on them when I took them off. Advice?

Thanks for everything...now, I have to get the car up and running in a hurry. My 1st cousin dropped dead of a heart attack yesterday in Norfolk, VA...36 yrs old. Wife and 2 kids. Isn't life strange? Hope to drive the car up for the funeral on Saturday.

------------------
John J. Meadows
'83 300D 3.0L 260k mi.
'85 190E 2.3L 99k mi.

Fifteen is plenty. It always takes more to break them free the first time they are taken down. You have to be careful with steel capscrews and aluminum threads. Can strip quite easily and believe me, you do not want to go there..

------------------
Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE