Hi,
I've just bought this car and I am trying to find the source of a oil leak, it looked like the plug for the timing chain tensioner, so I removed it to put some hylomar on the aluminium washer.
Can I just reinstall the plug or do I have to reset the tensioner.
Any help would be appreciated.
Thanks,
Grant.

When you removed the plug, it went to full extension.

What year is the 300?

Tom

It is a 1989 300te.
When you say it went to full extension what does that mean.
I've searched everywhere but can't find details on installing the tensioner.

By removing the cap, to the tensioner it is like having a very worn chain.

I have a screenshot of the M103 engine's (is yours 104)but it's too large to attach. E-mail me and I can send it.
Tom

http://webwench.net/w123manuals/Service/W124/w124CD1/Program/Engine/103/05-3100.pdf

Thanks for that. The engine is a M103.
All I have removed is the screw plug which is number 512 on that PDF. So i don't understand why I need to remove the whole tensioner and then reinstall it.
If I had removed the threaded ring number 510, that would make sense.
I'm obviuosly missing something, if you could explain it that would be great.

Shouldn't have to....the pin can only move to extend if the chain is moved or the tensioner casing/ring have been moved.
The cap/spring are just to supply pressure/force on the pin to extend as the chain wears/stretches.
...the problems guys have [ and they are big $$$$ mistakes] is when the chain/cam are changed and the pin is not reset to accomodate the new chain dimensions..........................
I have seen guys break brand new camshafts right in half !!!
You may want to go the extra step of pulling the pin just to see if it is worn and to see how far it has extended, as that is indication of chain wear/stretch condition

You are correct in that if you only released the external spring retainer cap 512 you have done nothing to affect the setting of the tensioner,you only have to reset the tensioner if you slacken the threaded ring 510.
Geo.

Not applying to your vehicle, which I guess by Arthur's comments, is a ratcheting type tensioner; for the older model's, like my 220D, the tension of the tensioner is all controlled by a spring and oil pressure. This type of tensioner can be removed, then refulled with oil by pushing tension rod in a bath of oil to refill it, then bolt it back in. I just thought it okay for this post so as to distinguish between newer ratcheting type and older typers. I think I'm correct on this. If not, someone more knowledgeable please correct me.

That is correct .. the reason they went to the ratchet type tensioner is b/c the oil bath ones would bleed down when the car sat for a while and had to refill when the engine was started to get the chain tight again.
So, the famous chain rattle when first starting on these old tensioners.. Many a chain would snap/jump at this first start up condition.
The rathet simply does not allow the pin to retract , regardless of any tensioner faults.
Much better design.................

Thanks for all your help