W123 200 (M102.920) timing chain rattle when warm. Please help!

[Werner200]

Hi guys. I'm in need of some desperate help. My car is a 1983 W123 200 4 speed (M102.920). I have recently replaced the single row timing chain and tensioner due to a rattling or tapping noise caused by the chain hitting the timing chain cover somewhere, although the problem still persists... There's already scraping marks on the outside of the new chain that shows that it is making metal to metal contact somewhere.

I have checked all the guides plus tensioner rail and it shows little to almost no wear. The noise is present at cold start for about 3-5 seconds then completely disappears till the engine starts to warm up and then returns. It is definately the chain causing the noise, no doubt about that. I have even smeared some grease on the chain to confirm and the noise would disappear for a few seconds. I'm running 20W50 oil here in South Africa. My oil pressure is pegged at 3bar on cold idle and 2 bar on hot idle.

It's almost as if the tensioner becomes none functional when at operating temp. I am clueless and don't know what to do anymore. Any help or information will be much appreciated.

Thanks

 

[balge]

£30 for a new tensioner, worth a punt?

 

[kth286]

Doesn't the tensioner rely on both internal spring ratchet assembly AND oil pressure ?

There must be an oil pressure non return valve in the front block under the timing cover to prevent the tension falling away.

The above is the way my later 124 works.

Perhaps this one way oil pressure valve needs to be changed.

 

[Werner200]

Thanks for the reply. I have fitted a new tensioner along with the chain.. Could this be that the tensioner is not receiving sufficient pressure once things are starting to warm up? Could it be a stuck oil pressure relief valve?

 

[Werner200]

Thanks a lot. I had the same thought but my oil pressure reading seems good on the gauge in the cluster. I will try to remove it today, thanks for the advice. Much appreciated!

 

[Werner200]

O.k I have removed the relief valve and it does not appear to be the cause of the problem.. Starting to lose hope now on this car

 

[balge]

If the chain isn't tensioned correctly the tensioner isn't working correctly?

I would try it on 10w40 as spec if it is hydraulic, I thought they were just springs

 

[Werner200]

Thanks Balge. I will give that a go and see what happens.

 

[kth286]

A thought.

With the 124 the tensioner has to be dismantled to refit.

The inner mechanism has to be pushed through the tensioner, and the inner then has to be inserted into place, and only then the outer part fitted.

Have you read the workshop instructions for the tensioner fitting ?

Was the above the required procedure ?

If so, did you follow it ?

 

[Werner200]

Thanks for the post. Yes I did reset it the correct way. I have worked with these tensioners before.

 

[Werner200]

I have changed the oil today to 10W40 but still no luck. Noise is still the same..

 

[Werner200]

It's strange to me that every Merc I had (all petrol versions) made a "woosh" kind of noise from the engine everytime you take your foot of the throttle to change gear. I'm guessing this is related to the chain slapping noise that I'm getting from my W123.

 

[Marku]

The tensioners are so simple it is difficult to see how they can go wrong. If the oil pressure is OK then the tensioner should function. Is it located on the guide correctly? Are all the other guides in place? Seems obvious but is the chain correct and not too long?

 

[Werner200]

Hi Marku. Yes all the guides are in place and the tensioner rail arm is in order. I have bought an EK (japan brand) chain and it measured 113mm. The old chain measured 116mm.. Do you think it can still be too long? Oil pressure reads OK on the instrument cluster. Never drops below 2 bar, even when very hot.

 

[Mbdude]

Hello Werner!

I am experiencing the exact same issue, a tapping chain. I have also replaced the chain and tensioner without luck and am now seeing new marks on the outsider of the new chain. Did you ever solve the problem or has anybody else an idea what it could be?
Thanks and greetings
Alex

 

[alabbasi]

Are they plastic guides? If so, a guide may be broken which would create slack.

 

[Martinroyce]

Hi guys. I'm in need of some desperate help. My car is a 1983 W123 200 4 speed (M102.920). I have recently replaced the single row timing chain and tensioner due to a rattling or tapping noise caused by the chain hitting the timing chain cover somewhere, although the problem still persists... There's already scraping marks on the outside of the new chain that shows that it is making metal to metal contact somewhere.

I have checked all the guides plus tensioner rail and it shows little to almost no wear. The noise is present at cold start for about 3-5 seconds then completely disappears till the engine starts to warm up and then returns. It is definately the chain causing the noise, no doubt about that. I have even smeared some grease on the chain to confirm and the noise would disappear for a few seconds. I'm running 20W50 oil here in South Africa. My oil pressure is pegged at 3bar on cold idle and 2 bar on hot idle.

It's almost as if the tensioner becomes none functional when at operating temp. I am clueless and don't know what to do anymore. Any help or information will be much appreciated.

Thanks

Hi
Did you ever get your timing chain sorted out? I am thinking of doing this myself but hesitating after reading your post. Thanks