There is this sound that has recently developed and the guys at the garage hasn't a clue what it is. Everytime the brakes are applied, there seem to be a knocking sound coming from the front. The sound is most apparent when braking down from 40 km.

With the brakes squeaking and now this knocking, makes me think that this car has some hidden and unappreciated talent.

What should I be looking for?

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

Greetings,

This sound you hear, is it coming from one wheel in particular and exactly what does the sound imitate? Couldn't be a moving brake pad moving in it's holder, could it? It could also be a strut rod mount or wheel end mount moving as the pressure increases.

Charles

__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan

Is it just one or two knocks when coming to the stop? Or does it knock, knock, knock all the way until stopped?

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Its only a knock when the brakes are applied, and then you'd feel the pressure of brakes being applied. Its irritates.

I asked the MB dealer and he thinks it could be the case of either:
1. a dirty ABS sensor, which needs to be cleaned; or
2. faulty brake relay.

I notice this morning that the knock was absent (a wet morning). So I conclude that it comes up only when its hot.

How will the strut rod mount or wheel end mount create this knock?

Thanks for the comments.

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

Greetings,

Forward vehicle motion forces the chassis weight to shift and causes movement of the strut rod into a loose wheel end mount causing a knocking sound or the guide rod on the opposite end shifts into the defective mount causing a metal to metal contact.


Charles

__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan

I am going to print this in hardcopy.

Thank you.

__________________
... Kerry

126 tailed by a 203, 129 leading the pack.

I agree with the strut rod theory. Someone outside the car should be able to see the tire jerk toward the rear at the moment you hit the brake pedal.

The following links will give your more info:

300SD Suspension Noise

Here's a question...

David