Rattle after engine mount replacement
 

Hi,

On my 1986 190E four-cylinder, I had a failed engine mount on the exhaust side that meant the engine vibrated a lot. This was replaced with (if I remember right) original parts, or at least good quality replicas (have heard bad stories about replica engine mounts..).

Then, the engine developed a rattle. It's heard best inside the car with the windows closed. It's the sort of rattle that sounds like a timing chain rattling, or as if someone left a screwdriver under the bonnet..

I replaced other engine mount, no improvement.

It's worst in 'D' at idle, still there driving at low speeds, not so bad in 'P', and gone in Reverse.

What's causing it? :confused:

Russell

Not an expert by any means (since I attempted to replace motor mounts on my W124 a couple of weeks ago...still can't get the bolt off the driver's side mount :mad: ), but it sounds like the new motor mounts cured the engine vibration, but exacerbated the transmission mount(s) if there are any. The clue to me is the different symptoms you are getting depending on gear selection...

I would also check your exhaust to trans mounting bushings if your car has these (my W124 does). After you replace the motor mounts, thereby damping the engine vibrations, all sorts of other noises become more apparent. The noise you describe could be these bushings, or, as G-Benz states, it could be the tranny mount.

Not sure I understand - if it's worst in 'D' and idle, those are conditions you can duplicate (with caution!) with the hood up and you looking around for the source. If you need to slide underneath, set it up completely on jackstands so the drive wheels are off the ground.

Might be a shield on exhaust of cat converter, if you have one.

Steve

yes, check the exhaust for clearance. if you had work done on it it may have taken a "set" with the bad mounts that is now causing a clearance problem.

you may need to remove some clamps and twist the pipes to eleminate it.

tom w

You are sure that the fan blades are not striking the fan shroud?

Did you check the exhaust to trans mount bushings?

Push on the motor
 

If it rattles with the motor running, push the motor to one side and then the other and see if the rattle goes away. Does it rattle on a hard right turn or a hard left? If so, you probably have bad mounts. If they are original Mercedes mounts and it is less than 12 months (unlimited mileage) from the date on your receipt, Mercedes will replace them including labor under their parts warranty. (The warranty information is printed on the back of your parts invoice.)

At 135k I replaced the original mounts on my 92 300d (they are the hydraulic ones) with aftermarket mounts. The motor rattled just like in your description and I figured that the noise was something else since I had new mounts. I changed the transmission mount and checked the exhaust mount and it still rattled. Then I contemplated changing the lifters, the idler pulley and all sorts of things until a mechanic leaned in the motor while it was running and caused the rattle to go away.
Year or so after that (at around 165k) the mounts collapsed so I bought original parts from Caliber. When I installed them all of the noises disappeared.

In your case, the original mounts cost the same as aftermarket mounts, are higher quality and have a better warranty.

Very common rattle on these is from the top bushing on the tensioner damper.
They usually show up at idle , in gear. Have someone do just that as you stick a screwdriver in at the bushing to tighten up the slack. You will see it right away and it can be cured by sandwiching an O ring around the mounting bolt to take up the side to side slack.

Archieves.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1M30LAGSC1TR0Z7Y9Z&year=1986&make=MB&model=190-E-002&category=G&part=Acc.+Belt+Tension+Damper&appEngines=_any

my post regarding checking exhaust for adjustment issues applies to the fan shroud too. it can be moved around a bit if it is hitting after the new mounts.

tom w