Timing Chains

Had a couple of great weeks off. Managed to roll in new timing chains on both my 78 300D and my 81 300SD. Interesting results.
The old 78 took to the new chain like a dog to a bowl of Alpo. Immediate improvement in performance and that annoying engine shake completely disapeared. Starts faster and runs sooo much smoother. I guess it was time for that one.
The 81 runs quieter. Have had so many problems with that engine anyway. There was a noticable timing chain racket on startup that is now gone. Replaced the tensioner and banana slide also. Probably a good thing to get that one done. However there is now an engine shake where there was none before. Checked all the usual suspects. No visable diesel fuel leaks, and no air bubbles at the filters.Have freshly rebuilt injectors already in place. Used new washers under them when they were pulled and torqued back in.
My question is, could the new chain have changed the IP timing a bit? Should I now be looking at that? Or am I missing something else here?

[surfblau]

Just wondering if the shaking is at operating temp or only when cold.

What was the mileage on these cars?

I think I need to measure my chain stretch...

thanks

Old dies,

Before I got to the last sentence of your post, I was thinking that you should check the IP timing. I prefer the drip method, but whatever works for you would be a worthwhile endeavor.

Good luck,

[gsxr]

To answer your question, yes, a new chain will affect IP timing. You should definitely check it. If it requires adjustment (spec is 24 BTDC I believe, +/- 1.5?) you may want to adjust to the far side of spec advanced (25.0-25.5 ?) to pick up a smidge of MPG. Just don't go beyond spec, or you'll get excess smoking at high RPM's. (Ask how I know. )

BTW, thanks for relaying the experience - I need to replace the chain in one of my cars (stretched 4 deg.), and this is giving me some motivation to finally do it. Just curious, how bad were your original chains (degrees stretched), and how many miles were on them?


Best regards,

[Diesel 924]

Do you have to use the special swaging tool on these chains or is their a chain that connects with ordinary tools?

[gsxr]

You are supposed to use the special tool. IMPCO sells it for ~$200 or will rent it for ~$40.

However, I have heard of people swaging the master link with a ball-peen hammer, using a small sledge as an anvil on the opposite side to take the impact. Supposedly it works great. I've never done it, I'm just passing along what others have done.

There is NO link that does not require swaging (i.e., "clip type" link) that can be installed permanently. Mercedes sells a temporary clip link - but the service manual is full of warnings that it is to be used during installation only, then removed and replaced with a "real" link before starting the engine.

There's a very informative PDF on timing chain installation at this URL. It is for OM60x engines but most of the info also applies to the OM61x engines too:

http://www.meimann.com/images/mercedes/W124_stuff/OM60x_Timing_Chain.pdf


HTH,

To answer the questions here my 78 has 349,780 miles and the 81 has 211,450 miles. I have driven the 78 since it had 254k miles. I do not know if the timing chain had ever been replaced and I never measured the stretch. I had a local MB shop look and listen to the 81 and he condemned the timing chain right off. Said that racket at start up was the chain getting ready to destroy my engine. I then pulled the tensioner and it was not looking too good either, so I decided the chains were only about $89 each, the slide was another $25, and the tensioner was $88. There were other costs, little gaskets, oil change, new filters, etc..
Not a bad repair to gain a little relief from that threat. And why not do them both? Might speed it up a bit.
I used the swaging tool to put them together. I had read here where you can use a ball peen and backing and that works. I don't know about getting the master link together though. The master link has the outer part that needs to be pressed on. The tool has a fitting to set the link in place and then tighten it onto the rest of the master link. That part would be difficult at best without the tool. I was given loan of the tool localy.
I had read several threads about doing this job and they were most helpful. I used small vise grips to clamp the new chain onto the cam sprocket and vise grips to clamp the old chai in place. Then just roll it in in increments. Set and made sure I had the TDC marked and pulled the fuel injectors out. Would not want the engine backing up in the middle of this.
To tell you the truth I was just short of terrified to take this project on. The only experience I had with timing chains was on my first engine repair. There I was at age 14. Put rings and bearings on an old Honda 160cc motorcyle. Then the timing chain.
You guessed it, I missed the marks and bent up the valves and pretty much wrecked that one. I swore off timing chain work at that point.
Larry, I think your analysis is going to prove true. The 81 will now need the IP timing adjusted. Thank you.

Surflau

The engine shaking is both with hot and cold. Starts up ok and the shaking smooths out a little when it warms. But remains there.