vibration from ML270 when cold

[Hedley Rees]

Recently I have noticed and increase in vibration from my ML270 CDI auto it is 5 years old and has done 62k miles

 

[Sprint'n'Go]

Only last week I was talking to an independant Merc specialist when this came up in conversation "The CDi engines are prone to injector problems"

My own experience would seem to back this up as I have had injector problems on 2 occasions. The problem manifests itself as a bad missfire when starting first thing in the morning but not every time. It starts ok but then runs rough for about 10-15 seconds and then clears and runs fine until next time. Also sometimes when starting a warm engine you will get a sharp cracking sound as it catches but no rough running. As I was still in warranty Merc fitted a set of 5 injectors which I was told would have cost £180each + vat + fitting(OUCH).

If this is your problem then you will need to replace any faulty injectors. I enquired what would they do if I was paying the bill and they said they would just change the faulty ones.

 

[oigle]

Would suggest that your problem will be with engine mounts gone hard. I have had mine replaced twice under warranty!! Each time the engine quietened down noticeably in operation after the replacement. The MB dealer said they have a problem with sagging and then going hard, particularly if worked hard - I do quite a bit of towing. The drivers side one is usually the worst culprit.
Not too hard to replace by yourself - remove wheels and protective skirt and they are there in your face. Need new attaching "rivets" to put skirt back on.

 

[psmart]

.... If you've got bull and side bars fitted, these also vibrate after a while because the fixture nuts shake loose.

I had bulls and sides fitted from new and Ive had to have them tightened up twice now.

 

[Sprint'n'Go]

the thing that puzzles me about this problem is that it is stated that the fault is when the engine is cold (in the heading). In my case, I have never noticed any differance in the idle quality when cold or hot as the modern engine management systems are so good at maintaining a steady tickover regardless. So would hard engine mounts or vibrating cosmetic attachments only show up with a cold engine?

Any comments Hedley Rees?

 

[oigle]

In my experience, I found the vibration much worse when cold. I figured the engine mounts softened up a little when hot, reducing the problem. I think that the engine itself also contributes a little more noise/vibration when cold, due to extra clearances piston to bore etc before things get to operating temperature. I know I had trouble convincing the dealer as to the magnitude of the problem when cold as he always drove it hot. The proof was in the eating though as it was great after the replacement, particularly the second time. The dealer service guy drove it after the 2nd replacement and commented how smooth and quiet it was. Maybe the mounts have been redesigned by MB as the 2nd job was much better than the 1st, as far as result goes.
I would almost guarantee this would fix your problem.

 

[Hedley Rees]

The vibration is when driving not idling and definitly reduces as the engine warms up but does not disappear. My reference to the drive train was picked up from The Top Gear WEB site (Jeremy Clarkson programme) where the ML was reviewed