Bad vibration at idle, 05 W211 cdi
 

Hi Folks,

I'm the 'new' owner of a 2005 E320 cdi with only 81k on the clock, the car had some things wrong with it when I bought it and I've been going through and fixing them, so far I've done:

air filter
oil and oil filter change
diff oil change
new engine mounts
new transmission mount
new thermostat


The problem I'm having right now is the engine has a bad vibration at idle, in drive, park or neutral it makes no difference, it has all new mounts so I don't think its that. I took it to the local mercedes benz dealership here (before I did the transmission mount) and they told me it was the trans mount that was shot and was causing it.
However after putting a new mount on the vibration is still there.

It also has quite a big kick, when I switch the engine off.

I did some googling and the best explanation is either the alternator pulley is bad (it has some kind of damper or clutch in it?) or one of the fuel injectors is bad and at idle is injecting just the wrong amount of fuel, causing the vibration.
It does need a new serpentine belt, so I'll get that done and check the alternator pulley when I change it.

Can anyone help? If I knew the benz dealer could fix it I would take it back, but they seemed more interested in billing me for other things and washing my car than actually fixing the thing I brought it in for.

Thanks

Chris

No check engine light? The dealer will find lots of stuff to fix on the way to solving the problem as the car is ten years old, just what it is. Worn parts are worn parts. You don't want to go down the replacing injector path if possible, that will cost a ton of money. Have them run a cylinder balance test and find out which cylinder is the most out, then swap injectors around and see if it follows the injectors or not. ($2000 for a set?). Always install new washers under the injector. Ream if possible the bores and make sure they are nice and clean. Same for glow plugs, they have a history of being a problem.
Vibrations on diesels are almost never caused by a weak mount, the vibration wore out the mount (meaning the mount alone is seldom the source of the problem). Weak sensors, worn injectors, internal engine issues can all cause vibrations.
I don't have first hand experience with that engine (OM648) to know what is common, but I doubt the serpentine belt would cause much vibration. More likely a shut down valve or shutter in the intake manifold is not working properly to prevent a shake when turning off the engine, these do make a big difference (but not while running) unless it is sticking from carbon build up. Maybe the intake is getting clogged up, have a peak at the easy to remove areas.

The dealer did find a laundry list, however they didn't really focus on fixing the problem I brought it in for, they should be able to do more than throw parts at the problem.

The injectors are expensive however from what I have read previously its normally a single injector that is off and causes the imbalance.

Is there a guide for removing and re-fitting injectors? someone told me to check for leaks between the injector and cylinder, can I re-torque them down or do I have to remove and put a new seal in?

Would a glow plug cause this problem? I thought a bad glow plug would cause starting issues, it starts up fine.

Thanks

If you remove the injectors you need to fit new stretch bolts, new seals, and you should ream the seats, or the seals will fail.

I took some videos, first the engine idling under the hood:

https://youtu.be/twWLpcObpDM

Secondly inside the car where you might hear the booming kind of vibration:

https://youtu.be/s2KBrQkcs3k


Another thought I had this morning, I don't remember this vibration being quite as bad before I changed the engine mounts, it did clunk more as the drivers side engine mount was failed and leaked all its fluid, the passenger side one was ok but I changed it as it was only a matter of time before it failed too.

Perhaps the new Febi mount on the passenger side is defective or just poorer quality than the OEM Benz one I took off?

I should be able to tell underneath if the mount is transferring the vibes through to the body.

Incidentally does the engine idle under the hood look good? to me it seem to idle fine, its inside the car the problem seems to occur.

I did some more research on the alternator pulley, its basically a one way bearing which engages when the alternator is sped up, but when the engine is slowing down dis-engages the alternator to let it slow down at a different pace.
The reason for that is the alternator has a lot of mass and could cause squeaking or slipping without the bearing.

It doesn't seem like this would be the source of my problem, I plan on changing the belt very soon as its old anyway so I'll check it while I switch the belt.

The idle seems fine to me, but I do not have any experience with that particular model. As for the inside cabin resonance, it sounds like it could be exhaust related. Just a stab in the dark, but I would check out all the exhaust system components and hangers and make sure there is no play in any of them. Good luck!!

Yeah it does seem like an exhaust throbbing/vibration, I'm going to try and check that out tonight.

I watched your videos, Sounds fine to me. My e320 cdi has 113 and sounds the same.