280 SL timing chain and tensioner

[drooman]

Before posting I read a number of threads on here about this, could not find my answers.

My (new to me) engine was a little clattery esplically when cold. Valve adjustment ensued. They were ready to be adjusted, a few a little tight, a few a little loose, nothing way out though.

When I first pulled the cover i noticed the chain was a little sloppy going by the guide rail near the cam gear, then as i turned the engine through the revolutions required for the valve adjustment I saw that sometimes the chain would be tight and sometimes loose.  I don't know if this is normal or not.

 I read up on checking the tensioner, and I can't get it to do what is described to "check" it. It is very difficult to move, in either direction. I pulled the chain guide off to get a good look/ access, it might move a MM in each direction, with a lot of force.

My questions:

1. Does the tensioner lose its tension after the engine is off for a while, then pump up when started? or, should it stay pumped up while parked?

2. do these things ever "seize up? I can't tell if it is pumped up and won't move, or seized up and wont move.

3. how tight should the chain be at rest? and does it matter where in the revolution how tight it should be?

I can't really evaluate the chain without getting the tensioner to act like i think it should. I need to do a thermostat and short hose under the housing so I'm pretty much ready to pull the tensioner out anyway.

Thanks!

[stickandrudderman]

There should be no slack in the chain at any time.
PLenty of info on here about renewing the chain and tensioner.

[drooman]

Well, answered one of my own questions. Pulled the tensioner out and the piston was totally stuck, so they CAN seize up. pulled it apart and cleaned it up, now it springs and pumps like it should.  the tensioner lever moves freely so the tensioner unit will go back in tomorrow to check for chain stretch.

[WRe]

Hi,
don't forget to bleed the tensioner: fill oil into the cylinder head pocket and push/pump the tensioner a few times and let it come out again, should go hard, check tensioner rail for marks.
https://www.sl113.org/wiki/Engine/TimingChain
...WRe

[ja17]

On rare occasions, I have had them bind-up during installation. Probably some kind of distortion and piston seizure?

[Pawel66]

You were also saying it is important to prime the tensioner during the installation with oil and manually pre-load it a bit.

[Benz Dr.]

I would replace the timing chain. If its been sloping around for a while that couldn't have done it any good.