Expert opinion required. Broken exhaust cam sprocket! (W124 E200 1995)

[flatsheep]

Hello,

I posted a week ago about a noise I was getting from the engine. The car had been into a garage for a timing chain and tensioner replacement. The garage only replaced the tensioner, not the chain. Since getting the car back I've been getting a howling noise from the engine up to 2000 revs.

I've been avoiding driving the car, as it's booked into a Mercedes specialist on Saturday to troubleshoot the car. Yesterday I needed to run an urgent task, so I had no choice but to use it. While out the car just died on me. I feared a broken chain, but the AA guy reckoned the chain may have skipped a tooth (hmmm).

Tonight I've whipped of the camshaft cover, and to my horror, the exhaust cam sprocket has sheered off! (See pictures)

My main query is: Is this likely to have been caused by the new tensioner being incorrectly fitted? Is it possible to over tighten the tensioner? What’s the cost of a new exhaust cam? If it were your car, would you get the garage to cough up for the work (assuming what they did was done improperly).

Thanks

David

Pictures!

 

[television]

There are several things to think about here, first the damage. As some of the exhaust valves will be open, some of the valves could be bent or the pistons damaged. the head will have to be removed to check.

How could this happen, if the chain jumped a tooth it would not cause the cam shaft to break, the pistons would not foul the valves with one notch, so one can forget that. Also the engine would have run so rough it would have been undrivable, The tensioner must have been incorrectly fitted, the oil pressure could not do it, and the car was oK before it went in, it would appear that the piston had released itself before or as the tensioner was screwed in. A very lazy way to change it, one always has the rocker cover off to check the free play on the right hand side.

malcolm

 

[kth286]

flatsheep

I warned you in your previous posts, this was likely to happen, and NOT to use your car until the timing chain tensioner was removed and replaced again.

It is very simple to remove, and replace with a new timing chain tensioner BUT there is a special technique applicable to your Merc, and a non specialist will probably not know.

The replacement of the tensioner means that the outer part is screwed into the block first AND ONLY THEN can the middle insert (as a stand alone unit) be screwed in to get the correct tension.

The whole tensioner must not be screwed in as a whole unit, but in two parts.

You need to get trade association/trading standards/solicitor involved and not meddle with it yourself.

I wrote:

" Did you take it to a Merc specialist ????????

There is a RIGHT way and a WRONG way for the tensioner to be removed and installed.

Get it wrong and you can end up with a busted camshaft at minimum and it happens !!!!!!

Get it to an expert if you are at all suspicious - it is not a big job at all - I will be doing mine in due course.

I would not be using the car until the tensioner had been replaced again by an expert, if it were me.

What made you think you had a tensioner problem in the first place".

Best of luck.

Regards

 

[flatsheep]

sorry

Hello kth286,

Yes, I bow my head in shame, I remember your post clearly, and had heeded the advice completely.

I did take it to a specialist on last Saturday, but they didn't know what was causing the noise; they could only fit it in the following Saturday. They gave me no warnings, etc. This was Mercedes First in Nottingham.

I think this proves an important point that if you ask for advice you should take it.

C'est la vie.

David

 

[bibamus]

I would be in contact with the garage that replaced the tensioner and explain what has happened as the damage ( as TV so rightly stated a while ago) was more than likely caused by incorrect procedures in fitting the tensioner.

Of course, the tensioner replacement may just have excacerbated the original problem, it depends on what your original symptoms were.

Allan

 

[Glenn Smith]

your garage has certainly fitted the chain tensioner incorrectly resulting in a huge amount of force on the chain and sprockets, most tensioners req re-seting prior to fitting, I would be having words, nothing else would cause the sprocket to fail.

 

[flatsheep]

The garage

I've called the garage that carried out the work of replacing the tensioner.

He reckons that he's done many tensioners in the past, without issue. He described a process similar to what was explained in an earlier posting. I put it to him that even if he had fitted the part correctly, then he should have tested that the chain wasn't over stressing the system. He fitted it and did nothing else.

He wants an independent assessor to review it (as to I) before he admits liability. If the evidence goes against him then he has offered to cough up all costs.

He isn't denying that fitting the tensioner has caused the problem, what he is saying though is that the tensioner was correctly fitted and that its a weakness in the engine that has surfaced as a result of the system being tensioned. My response to him was that he should have investigated further into whether fitting the tensioner would cause undue stress on the other parts, this is advice he should have considered before carrying out the works.

I'm looking at using Dekra as an assessor, any recommendations?


Thanks for your help so far.

David

 

[flatsheep]

Up the creek without a paddle

Hi,

No independent assessor will come out to the car and strip it to check . I reckon that to prove the incorrect fitment you'd have to disassemble the tensioner to check. If I were to remove it for them, then the chain would go slack, bang! all evidence lost.

Any tips on how I can prove that the tensioner was the cause?

Thanks

David

 

[television]

Any tips on how I can prove that the tensioner was the cause?

Thanks

David

The very fact that it broke the camshaft is enough, surely and that the car has been fine before that.

Malcolm

 

[gassed up]

snapped camshaft

The classic symptom of an incorrectly fitted tensioner (the outer must be fitted first, THEN the plunger) is a cam which snaps at the first journal. I'm a transport manager, in my fleet I have 4 LT35 trucks fitted with Merc 111 series engines and I have 1st hand experience of exactly the same problem. The garage was definitely at fault. These engines are normally good for 300,000 miles, unless they are seriously abused or maintained by the inexperienced.

 

[Ron Palfrey]

Look, we gave you advice before and you did not heed it. David has now advised you to involved the legal beagles. Why not listen this time?

Get your solicitor involved now.

Ron