W124 timing chain

[Williamwoo]

Hi all,

My car has recently (and very gradually) become very rattly at the front of the engine. I assume this must be the timing chain and/or tensioner. Is it an easy job to do (I'm reasonably competent mechanically) and is there anything else I should look at while doing it? The car has done 125,000 mile btw, and still runs perfectly otherwise.

Thanks in advance.

 

[Marku]

Short of taking the timing cover off, which can be a pain, the only way to replace the chain is to cut it. Fit the end of the new chain to the old and wind it through, with the plugs out, making sure that it runs over the sprocket and that it turns maintaining its position. When cutting take care not to let any metal down in to the engine. Not sure of the position of the guides in your engine but you should be able to see them from the top. If they need replacing then it is a matter off withdrawing the bearings through the timing cover to allow them to be lifted out the top. Again not familiar with your engine but it usually requires a slide hammer or an M6 bolt with a sleeve to pull them out. As far as anything else if it is not using oil I would leave it alone renewing valve seals etc although it is possible not to but I would remove the head.

 

[RichardF]

Before you tackle this it's worth checking it's not just some ancillaries rattling around.

 

[Williamwoo]

Thanks both for the replies. 'Rattling ancillaries' sounds like something worth checking out when I'm back home. Unfortunately however, I suspect the noise is too loud for that! (Might be a good name for a folk group though.)

 

[martyz]

I would doubt it's the chain,main culprits;aux drive belt tensioner,alternator bearing.

 

[drwizz]

my W203 has a dry bearing type noise and can i find it lol nope

 

[RichardF]

I would doubt it's the chain,main culprits;aux drive belt tensioner,alternator bearing.

I had the alternator thing, sounded for all the world like a knackered camshaft.

 

[Moth]

I doubt your chain will need replacement, especially at relatively low miles like yours. I have an idea what your rattle is though...

When my car reached around 120,000 I had a nasty rattle from the front of the engine develop too. The culprit was an easy fix. There is a little damper for the tensioner, easily visible, and they tend to give up - the rattling can come from a worn / enlarged mount where the damper bolts on at the bottom. When I held a screwdriver firmly against this lower mount with the engine running, the noise stopped. Some people simply use extra washers to take up the slack and stop the noise.

The damper is a cheap part, but a tip - the tensioner should be replaced at the same time to save you going back in there... ask me how I know! The system doesn't like to be fiddled with and even if the damper seems the only culprit it is very likely that the tensioner is not far behind.

Good luck.

 

[Bellow]

Remove the filler cap with the engine running. If the noise gets louder then it is internal.

 

[Newera]

Using a simple piece of tube in one ear with a screw wedged into the other you can make a simple stethoscope. Put it where you think the noise is coming from and you'll eventually find it as it'll be loud...

Drive belt tensioner is a common fault and found as described above.

 

[Williamwoo]

Thanks all for the advice - as soon as I get time to investigate, I'll let you know what it was!

 

[Williamwoo]

Hi again all,

I've at last had time to investigate further and have discovered that it is the bearing on which the viscous fan is mounted that is the culprit, and horribly rattly even when spun by hand. Presumably it is not included when purchasing a new viscous fan itself? Is it easy to change the bearing?

I've searched these esteemed forums for similar issues but seem to have drawn a blank. Everything else mentioned as possibly culprits (alternator, water pump, tensioner) seem to be as smooth as silk.

Cheers.

 

[carat 3.6]

Hi again all,

I've at last had time to investigate further and have discovered that it is the bearing on which the viscous fan is mounted that is the culprit, and horribly rattly even when spun by hand. Presumably it is not included when purchasing a new viscous fan itself? Is it easy to change the bearing?

I've searched these esteemed forums for similar issues but seem to have drawn a blank. Everything else mentioned as possibly culprits (alternator, water pump, tensioner) seem to be as smooth as silk.

Cheers.

Is it the viscous coupling itself that is rattling, or the bearing behind the pulley?

 

[Williamwoo]

Is it the viscous coupling itself that is rattling, or the bearing behind the pulley?

The bearing behind the pulley.

 

[carat 3.6]

The bearing behind the pulley.

That bearing is a special design, you can only replace it by buying the entire mounting bracket with the bearing in it.

 

[Williamwoo]

Ok, thanks, I suspected as much - presumably it's a dealer only part?

At a quick glance, it look reasonably straightforward to remove - about 4 13mm bolts I think (am not at the car at the moment). Any nasty surprises that you are aware of?