I replaced my Hydraulic Tensioner wile redoing my chain and it doesn't go back in. (BTW The new tensioner comes without a spring and the 19mm cap that bolts on the outside and I guess we should reuse our existing spring and cap...)
The telescoping part of it pressing on the Banana Slide prevents it from mating to the side of the cylinder head. I have never remembered this happening before.
I tried to lightly tap the telescoping head back in with a rubber hammer, but it won't retract. I read somewhere there's a trick to this. The Frankenstein solution of trying to mate it to the block by slowly tightening down on the mounting bolts and compressing the telescoping part--I know enough not to do that.
There's a trick here and embarrassing enough I cannot remember it...though once I did a workaround by removing the camshaft gear and then I put it back on. Can anyone jog my memory?

so much for driving the car tomorrow --!!

The newer one has a ratcheting action either as a safety feature or to keep it backing up when empty. Probably quite stiff when new. If I guess right you have to disengage it somehow to retract. Try dropping hunter a note. He might know. I do not. The factory service manual either on line or if you have one should explain the proceedure as well. Sorry I cannot help. Perhaps someone with more knowledge will respond. I also may be misunderstanding the problem. Would not be the first time for that.

Thats what I think it is...sighhhhhhhhh

Thats how I broke my old one. They ratchet. Use a screw driver or punch and push the end straight out, then stick it back in through the hole where the bolt goes. It's simply a one way ratchet. There is a bit on a "blockage" when fully retracted to it won't fly out if the spring is still in. Just give the screwdriver or punch a good tap and it should come right out.

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Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section

I have heard mention of these ratcheting tensioners before. I believe the cure for your dilemma is:

1. Remove cap and spring.
2. Push tensioner plunger out in direction of tension (would be toward chain)
3. install tensioner housing on engine, insert plunger, then spring, then press cap into place over spring and tighten cap. (tensioner should ratchet itself out to proper preload on chain as you squeeze spring.

If anyone else knows something I forgot, chime in, but I'm pretty sure this was the procedure I'd seen.

-Chris 80 240D w/617

That's exactly the procedure required...........

One Last Question. I'm pretty sure this thing will fill it self with oil through that little port, right? Thanks everyone! I can put it in "Dry" without putting a squirt of oil inside it?

YOu take it apart and reassemble it from the back, ie take the tensioner piston out the front an reinsert from the back.

You can. But a squirt of oil won't hurt it any..............

If it were my car, I'd replace the tensioner spring too. You should be ok with starting and running the car with the old spring. But at some point my recommendation is to add the spring into your next parts order and replace it.

Not as critical on the turbo engines as on the 240D (the 240D tensioner has no ratchet mechanism, at least not in 1981 models) but still you don't want a broken spring.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

The older I get the less I know............and the more mistakes I make

You did not create any errors I can think of. When you were not sure you asked on the site. Got lots of good clarification other than from me as I just did not know. My son in law went over to address his dragging front brakes on his new to him 126 gas the other day. Turned out he had separated the caliper bodies. Nothing would be gained by my being critical at all. Only wonder if they will seal up again. May not be a question when we examine the pistons and bores. I guess I will get a shop manual for him. I want him to think for himself as much as possible.

If he's anything like myself, thats the best way to learn, you remember it better that way too, I could read a book on something a million times and never remember the next day, but after examining and fussing with something new for a few hours I can work wonders. I had a problem with mine being stuck on once I hit the pedal when I got it, drug it off the trailer and found that 4 yrs of sitting had got the caliper slides pretty crummed up. Nothing a scraper, wire brush, flat file, and disc brake lube didnt fix right up...