Mercedes 300SD Timing Chain

[bpopilek]

I still seem to be having no luck with this pain in the butt! This is where I am right now. I bought a new tensioner, the old one snapped in half, and when I install it the chain continues to get super tight. What I think I have figured out at this point is there is some slack in the chain at some point. I removed the oild pump to see the crank sprocket and saw a little slack there, got that out, but still no go. When I line the cam and engine at TDC and turn the motor over 4 or 5 times and then check the timing, it is off. The other thing I notice is when I turn the motor over, the chain gets loose and then tight. Should it have the same amount of tension the entire time it goes around? Is there any way to see where the slack could be and how would I get it out? Thanks!

-Brian

Originally Posted by podunk

if you can turn the motor over 2 turns with no locking or binding , that sounds as if it is working properly
I would say it is unusual for the chain to be that tight without the tensioner installed.
But if you are sure that you have the right top gear and the right chain and it is timmed correctly I would put it together and listen for an awful noise while cranking.

The chain leaves the top gear to the right and goes down through the guide and is fed around the the injector pump drive gear through another guide then around the crankshaft , across the tensionning rail back to the top gear .

There is really no place for a kink to be without binding, if the parts are correct I think you are fine.

[podunk]

OUCH !!! friend after that being said (about the timming being off AND the chain being super tight) it sounds to me as if the top timming gear has 1 (one) too many teeth on it and I believe you could have the wrong gear. Try holding it back to back with the old gear and see if they are the same diameter with the same number of teeth. If they are not EXACTLY the same the new one will not work.

as for the intermittent slack, I believe this can only mean the injector pump drive gear is or the top gear is no longer running concentric meaning something is bent maby the fuel pump drive shaft or somehow the end of the camshaft itself although it would be a feat only king kong could do.
It is hard for me to isolate this problem when I am not looking at the situation, I am glad to continue TRYing to help all that i can!!!

[bpopilek]

No, I did not replace any of the gears, or the chain. I replaced the chain tensioner that pushes on the guide rail. As for any parts that are bent, I do not see how they could be, as I have not put excessive force on anything. This whole thing is just starting to irritate me more each day! hehe. If there are any other suggestions from anyone else, please let me know. Thank you.

-Brian

[podunk]

The new head gasket thicker than the old by very much ?

[bpopilek]

Originally Posted by podunk

The new head gasket thicker than the old by very much ?

The old one was just the slightest bit thinner, which I believe was from being on the vehicle for so long. We Are talking a difference of maybe a sheet or 2 of paper in thickness difference. I did have another thought that I am going to try tonight and see if it works. I seem to keep getting some slack at the crank sprocket and I think I have devised a way to get the slack to the top. I'll keep you posted! Thanks!

[j_hef]

So what did you eventually find? and what do you think caused it? I'm about to pull the head off a 300TD motor and want to try not to do what you did

[bpopilek]

I ended up figuring out that I did not have the tensioner set correctly. What I thought was that the tensioner moved in and out on the spring and in actuality it only moves out and locks. I had to take the plunger all the way out and feed it back through the backside after I got the timing chain all re-connected and everything was fine.

[podunk]

awsome dude !!! way to hang in there man