Engine cover creating noise (W211 E320 CDI I6)

[jeremy156]

I have been trying to track down the source of a resonating and rattly noise from the engine bay of my 2003 E320 CDI (inline 6 type) and have finally identified that it appears to be the plastic engine cover that's buzzing. I assume this cover is present to provide sound proofing, so it is somewhat ironic that it's now responsible for the noise that's annoying me, but I just had the car round the block with the covers removed and it lost that "something's loose" sound and came across as much more "together".

So.... my question is around quietening that cover down. Does anyone else find that theirs resonates when given a good thump? It appears that under the main cover, there's an inner plastic section which is glued in place and isn't entirely firm throughout, so I am thinking I should try to strengthen the bond.

My first thought is duct tape, however I don't know what sort of temperature resistance that stuff has - and with the engine running at 90 degrees internally, what sort of temperature the engine cover itself gets to.

Any suggestions or experiences would be welcomed.

Thanks,
Jeremy

 

[franey]

Buy a new cover?
They are not that expensive me thinks.

 

[corned]

I've got the 320CDI I6 motor, and the cover is silent!

I thought it was a single-piece moulding? There is a separate moulding which covers the inlet ports, which clips underneath the main engine block cover - is this joint causing the rattle?

 

[jeremy156]

corned - it's actually the larger of the two pieces I'm having trouble with. When you take it off, you notice there's a pale cream coloured plastic piece underneath and I think that's not entirely firmly fitted to the rest of it.

franey - I checked the Mercedes-Benz Parts, Inchcape site and it looks like best part of £100 for a replacement (!!!) hence my desire to find a way to fix myself first

 

[corned]

Time for the superglue/araldite/etc then!

I would not recommend duck tape or anything like that as it will just not bond sufficiently well to effect a permanent repair. The adhesives above, on the other hand, should. And they will handle the temperature.

I can testify to the suitability of araldite - it held a spark plug in a stripped thread on my old E-Type for 3 years!

 

[jeremy156]

I'll set to work with the glue then, thanks for confirming araldite is OK for the temperature.

 

[jaymanek]

You have more than likely lost the foam that is supposed to sit between the engine and the cover.

Part Number A6480160624

 

[jeremy156]

I've decided to take a photo, you can see the foam is in place (although barely stuck in places) - but I'm sure sure the grey/ cream plastic bit is loose and doesn't appear to have any screws, just glued areas.

 

[corned]

Oh, I'm going to have to go and dismantle mine now to compare them.

 

[proser]

Are you sure it's not rubbing against the airfilter box, as mine does .

 

[corned]

Can't get the torx screws undone! I only have a flexi-drive for torx, and it is bending before the screws give way. So I can't help just now I'm afraid.

Sounds like a splash or two of araldite in the right places will sort the problem out though. Might want to put a dab behind the foam to secure that too.

 

[jaymanek]

No not that foam.. there is another bit of foam that sits between the injector tops and the cover.. its about 2" thick!

 

[jeremy156]

jaymanek - thank you so much! I am glad I posted the photo now, otherwise I would have just said "yeah, there's foam" thinking you meant the thin layer all over it - I had no idea there should be a chunk of foam directly above the injectors, but it makes so much sense.

I've taken a snapshot from the EPC, I take it it's the part number 25 you mean?

 

[jaymanek]

yes!

 

[jeremy156]

You're a star, Thank You!

 

[BlackC55]

have you considered that it could be worn engine monts causing the covers to vibrate more?

 

[jeremy156]

Yes indeed, I do believe the engine vibrates more than it ought to, but assume that replacing engine mounts is likely to be an expensive job. Would it be fair to say that this engine shouldn't be trying to shake and that there is something mechanically wrong causing the vibration in the first place (that the engine mounts are having to absorb)? If the engine is vibrating excessively, I'd imagine it would eat its way through a replacement set of engine mounts too and would want to focus attention on the things that would cause vibration.

In principle, I understand the inline 6 to be inherently stable assuming all cylinders are firing equally. That it vibrates would suggest that some cylinders are pushing harder than others I guess....?

 

[corned]

It's a diesel. It is never going to purr like a petrol equivalent - particularly at idle speed.

Mine vibrates slightly at idle - I can sense it in the cabin - although it is slight. Nothing like the 406 I had before, which was very noticeable!

Once on the move and there's no noticeable vibration at all - very smooth indeed.

A little vibration at idle is nothing to worry about.

 

[BlackC55]

I tell you what. Drive the car to me and I will tell you if your mounts are bad or not. I won't charge you and I dont expect the work out of it either!

I will give you my honest opinion.

 

[jeremy156]

That's a very kind offer - PM on its way...