After a couple miles of drive and when come to a stop, either at stop light or parking lot, I can hear some kind of intermittent knocking from the cabin.

Had my wife drive. Back to parking lot, she holds the brake at DRIVE position. Open the hood, knocks is at the fan area. If the brake is released (while on D), knocks disappear. I used a HarborFreight stethoscope to listen to the area (alternator, pump, fan bearing, engine). No knocking. The only area I can't test is the rotating fan clutch.

Could it be the fan clutch need to be replaced or else? Strange is it only HAPPEN AFTER A COUPLE OF MILES OF DRIVE, BRAKE AT DRIVE POSITION.

Any suggestion?

On my 99, a collapsed left motor mount manifested as vibration at the serp belt tensioner. That vib can sound like a knock that gets better as the engine warms up.

You can release the tension on the serp belt (remove the spring) and fire up a COLD engine and run it for 30 secs to see if the noise is belt/accessory device related.

To check the motor mounts, use a rubber bushing between floor jack and oil pan and lift the engine ~1/4" and see if the noise/vib disappears. Dont lift more than that or you can damage the hard connections between engine and exhasut, fan/shroud and/or air filter housing.

Also check the bushings at both ends of the damper (shock); sometimes they fail which causes a clicking/knock.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

In addition to the above (which tells why it only happens with the brake), check your lower radiator core support. It is probably bent toward the engine, reducing the clearance to the fan blade.

Thanks Terry. I'll check it out.

Thanks Matt L. I'll check them out.
So . You guys do ntt thing the fan clutch has anything to do with the knock.

When the foot brake is applied with the car in drive it cause the engine to tilt slightly from the horizontal, this maybe enough for the fan to touch something -

You could take the fan off and try it for a bit.

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David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)

Much easier to release the tension on the belt so the fan doesnt turn; or just hold onto it so it can't spin.......

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Yup, easier to loosen the belt I guess, those bolts holding the fan on can be a real pain to get undone -

I would be careful about holding it though just in case it is bust, if the fluid has leaked out of the coupling it could grab with metal on metal contact.

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David


1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)

Hi all,

I found the problem.

After driving a couple of miles, when brake in DRIVE, DOWNHILL, I can hear the noise. The fan blade is touching the rubber fan cover at bottom left (when looking down front of engine). There is a mark on the fan cover.

When I had a helper hold the brake in DRIVE and give a sudden gas (I mean diesel), the driver side of the engine jumps about 2" while 1/2" the passenger side.

As Terry suggested. It is definitely the engine mount that cause the tilt of the engine and fan to touch the fan cover in DRIVE.

The question now is which one? How do I know it is defective? and how to replace it?

Again Thanks.

Don't worry about which side. Just replace them both, period. Not too difficult of a job if you are handy. Lot's of info on the board if you search, but basically you undo the mount bolts, jack up the engine using a board under the oil pan, pull the old mounts, and replace. You will have to jack up the engine more to put the new mounts in, because they will not be collapsed like the old ones.

The difference in smooth running is night and day, you will be amazed.

Rgds,
Chris W.
'95 E300D, 279K

Hi Chris W.,

Thanks. Are there only two or three. I saw two near the back. But can't see at the front, underneath the engine.

sam

There are only two; each is made by a different manufacturer with diff firmness rubber compound.

The mount that comes with the rubber boot is for the left (drivers) side.

Do them both.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Great. I'll just replace both.

Just take another look. Start the engine, give gas, the driver side is definitely bad. Look at the epc code (https://epc.startekinfo.com/epc/home.jsp), the part lists are: A 202 240 22 17 for left mount and A 202 240 44 17 for right mount.

Will call the dealer.
Again. Thanks guys.

Sam