Chain Tensioner going?

[NordikWolf]

What is the best way to tell if the Chain tensioner is going on the fritz? A friend of mine has a '87 420SEL and had the top end rebuilt and new chain rails installed. The car was running great for months but when it was started last nite the "marbles rattling in a tin can" sound came from the motor. Removing the oil filler cap you can hear it louder. Shut off the engine and he called his mechanic. He said to bring it back in tomorrow. Well, started it up today and it is quiet as a kitten! No noise at all, even revved up to 3500 RPM's!. Let it heat up, shut it off, waited 3 hours then started it up again and it's still quiet. Could this be the tensioner clogging and sticking? The mechanic said he did not replace this when the top end was rebuilt.

[Lenny Lipscomb]

I replaced the timimg on my 300 SEL at 100K mi. I replaced the tensioner at the same time as per MB recommendations. These things are a curved metal shoe with a plastic wear surface.(at least on the 103). Mine showed significant wear.

[gpracer]

I had the same exact thing. Changed my timing chain. Still there. Turned out it was the bearing bracket for the fan. Grab the fan with both hands (with gloves) and check for play. You can use some force since the belt tension will be holding it towards the ground......lift it up, wiggle it around and see if there is play in it. Mine exploded (the bearing) and took out the belt.

It could be the belt tensioner too, and not the chain tensioner at all. Belt tensioners when worn out will sound like you described and are very common issue.

Someone explained to me that chain tensioners rely on oil pressure, similar to a hydraulic valve lifter, and when weak can also have similar sounds, I am told, but maybe someone who knows for sure will chime in.

[newr]

Could it be the valve lifter noise?

[NordikWolf]

That's what I was thinking. It has been quiet for 2 weeks now. Guess I will have to pull the valve covers and have a look inside. Maybe I should just buy all the parts and do it anyway just to make sure. Anybody have luck with using the pin pullers available on ebay for $45 or am I wasting money and just use a screw/washer setup like most guys who did this work do?

[r_p_ryan]

I just used a bolt and yanked it out, but that was on the M103 motor...

[Strife]

My tensioner was definitely leaking and degraded at 88K on a 560sl when I changed it this spring. You shouldn't have to take apart the engine to replace it, just the RH valve cover, the bottles (maybe, on your car) and the alternator bracket. Interesting: I got mine with a "this side up" on the box (which no one paid attention to...). Some oil leaked out. I pumped it up as far as possible. Then I couldn't install it, so I pushed enough oil out of it to just barely permit catching the screws to draw it towards the block. I did this so that it would be fully pumped up the moment that I turned the engine over after reinstallation. I'm not sure that you need to do this but it seems like a good idea.

I used the pin puller on the guides and felt that it was worth the money. I think you would need to notch the washers in order to do the "bolt and washers" method. I would NOT use the slap hammer tool or method - unless you want to use the radiator as a backstop. One of my pins came out like a rifle shot and who knows what would have happened with the slap hammer.