Crank Pulley - OM642

[Alex225]

Afternoon all. I have just had a full service carried out on my S320 (W221) and my mechanic pointed something out that he thought it was worth me being aware of.

He had the car running and pointed out that the crank pulley looked like it had a slight wobble. I wanted to know a couple of things -

Is this a common fault issue/characteristic?
Huge implications if it fails?
Unsafe to drive?
Would it throw up an error on an iCarsoft MB if there was an issue?

Somewhat concerned as only had the car 3 weeks now and I'm due to do around 500 miles this weekend.

I'm hoping i'm just flapping unnecessarily but at the same time, if I need the garage to look at it again then they can.

 

[Londonscottish]

I had a problem with my 211 E500 on holiday in France and the AA patrolman spotted that mine was on the way out.

I decided not to risk the 600 mile drive home and had it fixed locally.

I guess it it lets go or throws the belt you at least lose the alternator - maybe more, not sure.

 

[Londonscottish]

You are being redirected...

"Because the crankshaft pulley drives the serpentine belt and all the accessories including the water pump, alternator, power steering and a/c compressor if it fails you won’t be able to drive your vehicle."

Of course it might just wobble away for several thousand miles. I've no idea.

 

[Bellow]

You really do not want it breaking loose at anything approaching high rpm. It is also there to protect the crankshaft. Change it as soon as practically possible. If you decide to use the car for the 500 mile intended trip - keep the revs as low as possible. Not to minimise the chance of failure but the consequence of it. I have no idea if there is 500 miles left in it!

 

[KennyN]

IIRC it is quite easy to release the tension of the belt on the 642 lump.

I would take the tension off the belt and have a "wiggle" of the pulley any play and I would have it repaired , as if the pulley is rattling on the crank for any length of time it could damage the location surface of the shaft and that would be a serious expense.

I am surprised your mechanic didn`t have a wiggle before the car was picked up , that way you would know exactly where you are.

K

 

[Bellow]

IIRC it is quite easy to release the tension of the belt on the 642 lump.

I would take the tension off the belt and have a "wiggle" of the pulley any play and I would have it repaired , as if the pulley is rattling on the crankfor any length of time it could damage the location surface of the shaft and that would be a serious expense.

I am surprised your mechanic didn`t have a wiggle before the car was picked up , that way you would know exactly where you are.

K

If that is what it is I'd park it up right now.

 

[Teego]

Get your man to have a closer look and take your other car for the weekend.

 

[Alex225]

There’s no play in the pulley, I have a video of it but the more I look at if the less it looks like it’s wobbling and more the the edge isn’t quite clean/straight.

Survived the 260 mile round trip I needed to do. I’ll try and upload the video.

 

[Alex225]

Hopefully this is a bit clearer. Bear with the file it's quite a large .gif from the clip I have on my phone.

 

[KennyN]

The inside of the pulley looks to be running true enough , whereas the outside retainer ring looks to have a bit of the "throw" to it. Give it a clean and see how it looks when running.

If there is no play between the pulley and crank with the tension off the belt then i would imagine it will be fine.

What gave your mechanic the impression there was an issue , did he just look at it or did he delve deeper ?

K

 

[clk320x]

Looks ok to me Alex

 

[Bellow]

You are being redirected...

"Because the crankshaft pulley drives the serpentine belt and all the accessories including the water pump, alternator, power steering and a/c compressor if it fails you won’t be able to drive your vehicle."

Of course it might just wobble away for several thousand miles. I've no idea.

The linked piece describes the pulley as being a harmonic balancer. Therefore, the most vulnerable part is the rubber between the inner and outer parts of it. Doesn't matter how secure the hub is on the crank. If the rubber is failing then the motion of the outer ring is freed from pure rotation.
Also, if the rubber is damaged then it is less likely to be damping as it should. Crankshafts have been known to break because of this.

 

[Alex225]

What gave your mechanic the impression there was an issue , did he just look at it or did he delve deeper ?

I think it was purely how it looked and being extra cautious he said it was worth getting looked at.

He admitted he’s not a Mercedes specialist so wouldn’t be work he’d do himself. I think perhaps he’s just being extra cautious.

He carried out a major service on it and then gave it an inspection. Overall he seemed very impressed with the car and it’s condition.

 

[Bellow]

One last shot before I surrender to false hope.

Crankshafts have been known to break because of this.

Crankshafts have been known to break because of this

 

[Londonscottish]

The linked piece describes the pulley as being a harmonic balancer. Therefore, the most vulnerable part is the rubber between the inner and outer parts of it. Doesn't matter how secure the hub is on the crank. If the rubber is failing then the motion of the outer ring is freed from pure rotation.
Also, if the rubber is damaged then it is less likely to be damping as it should. Crankshafts have been known to break because of this.

FWIW the diagnosis on mine was that the rubber was failing and it was only a matter of time before the whole thing came apart. It's a relatively common fault, apparently.

IIRC the car was around 10 years old at the time and on something between 120k and 130k.

 

[Bellow]

Also, any torsional oscillations at the crank's nose will be fed directly into the valve train via the timing chain(s). Not nice!

 

[johnsco]

The way the pulley is running looks like it is the rubber in the vibration damper that is slowly failing.
In this case, you shouldn't have experienced any wear due to frettage between the pulley and the shaft.
It should just be a case of removal of the pulley and replacement.
As said above, the vibration damper is required on certain engines to prevent harmonic vibration in the crank-shaft that can lead to premature failure.
Some engines are naturally-balanced (V8s for example).
Some are not ...... V6s, if I remember correctly.
Many larger engines of all configurations use a damper.
I remember I had one of my 1974 Chevy 350 cid V8.

 

[Alex225]

Thanks for all the helpful info guys. I've sent a message over to the garage and I will get them to take a look. As you all know I've not had the car long but I do get that it's 12 years old and hopefully they'll be happy to have a look at it. I mean technically they don't have a choice but you know what I mean haha.

 

[Alex225]

Forgot to update this thread.

I sent a video over to the garage I bought from, their advice was that it was fine.

Also got my car in with DDR in Surrey for a gearbox service and asked the chap to take a look. He confirmed it was also fine.

He explained that they often look off kilter due to the dirt or label inside the pulley. But that mine is absolutely fine. Did advise that If it was problematic I’d definitely know about it.

Good times.

 

[clk320x]

Excellent news