W124 300D Engine Rattle

[sowlerthjh]

I have a 1990 300D W124 auto. It has a problem with the engine rattling.

When the engine is idling, it has a clicking sound coming from the front of the engine. The noise stops once the revs have risen to just over 1000 rpm, and the engine runs completely smooth.

When the engine goes back to idling, the rattling starts again.

What could the problem be?

Regards

sowlerthjh

 

[panason1c]

Could be timing chain/tensioner worn, how many miles?..what rpm does the engine idle at? (too slow could cause a rattle)....what is the engine oil condition and level?

 

[sowlerthjh]

The car has done 182000 miles.

The engine idles at about 700 rpm on startup, then settles at around 500 rpm after some use.

The oil is changed every 5,000 miles and is at the right level.

I don't beleive that the rattle is due to the idling speed. Therefore, it sounds like the timing chain/tensioner. How does one check this and how long would it take?

 

[mjtray]

Could well be your timing chain, especially if you are still on the original at this mileage.

Could also be noisy hydraulic lifters which click away at low revs.

This is due to a faulty lifter that bleeds down at low revs causing the clicking noise.....sounds like an old typewriter! Mine clears at about 2000 rpm. I have consulted my local indi and he has advised me that its nothing to worry about, unless it becomes constant throughout the rev range.

Mine has got better as a result of using an engine flush just before changing the oil.

Another source of a hammering noise is a blocked injector....the noise it makes is called nailing as it sounds just like somebody banging in a nail very quickly.

If this sounds more like it try some injector cleaner. If still not cured you may have to replace an injector

 

[Jeff T]

I too had a horrible rattle from the front of the engine on my 190e. When changing the fan belt last week I discovered the bottom mounting bolt for the alternator was loose. Tightened it and now engine runs nice and quiet. Worth a look.

Goog luck

 

[sowlerthjh]

The problem is now sorted. I took it to an indepent expert.

Initially they thought it was the timing chain. However, further investigation revealed that it was a problem with the fan belt and tensioner.

Apparantly if you can stop the rattle by pressing on the tensioner of the fan belt, then that is where the problem lies.

I had the belt, tensioner and tensioner damper replaced for about £160 inc VAT.

Thanks for the help

sowlerthjh