603 Timing Chain Tensioner Problem
 

1987 300SDL

I removed the timing chain tensioner today to fix a pretty good oil leak. First off, I vaguely remember there being a copper crush washer being used as a seal. Is this correct? Dealership put a new head on the car awhile back, could it be possible this washer didn't get replaced?

On to the bigger issue...

It doesn't seem like the tensioner slide will retract far enough to allow the tensioner to fully get screwed in. The tensioner piston gets pretty hard to turn, then becomes impossible to turn without force when it has about another 1/2 inch or so to go. I took the tensioner back out and it compresses as it should. No issues there. I can't think of a way to make that slide move in farther.

What the heck......

Anyone?

does that tensioner eject itself like the 617 tensioners do? can you push it all the way through it's travel and back again?
John

It's not a ratcheting type tensioner, but I am able to push the piston all the way through its travel without issue.

There should be a copper or aluminium washer between the tensioner and the head.
Did you try to turn the crank by hand a little (taking the slack out of the chain)?
Maybe someone forgot or used a thinner washer between the belt tensioning lever and the timing case cover, causing the bolt of the belt tensioning lever to protrude to far inside/getting into contact with the chain tensioning rail?
Not sure about the 603, but could happen on my 662 (korean 602).

The seal is aluminum, and there are 2 sizes, early & late. Make sure you're using the proper seal for your tensioner. The early/small tensioner was superceded by a newer/larger version for improved sealing.

That said, it sounds like something is screwed up with the timing chain. The tensioner should turn in pretty easily until it seats against the cylinder head. You may need to pull the valve cover and peek inside the timing cover to see what's going on. Might as well check chain stretch while you're in there.

:sultan:

There is a button (I'm assuming the slide) on the inside of the hole the tensioner screws in to. This feels like it's spring loaded. If the crank bolt is turned CW, the amount of distance this button can be pressed in changes. Would anybody have a good diagram of what it looks like inside to see exactly what we're dealing with. I have the MB 602/603 engine manual...but it's not very "pictoral".

Its the chain you press against (via tension rail), distance changes a bit when chain gets tensioned by turning crank cw.
For pics see here and there
(thanks to gsxr).
In the second image you see hole for the belt tensioner lever bolt, the tensioner rail is just behind it.

What is the size of the hole that the tensioner screws in to? I'd like to clean up the threads a bit. It looks like it's either 23 or 24mm with a 1.5 pitch...is that right?