vibrating brake pedal - PeachParts Mercedes-Benz Forum

sublakedesron · #1 05-03-2008, 02:53 PM

(Car 1978 300D) When i use the brakes my pedal vibrates like drr...drr...drr...drr... and they have gotten real weak you have to stand on the pedal to stop. would warped/pitted rotors cause this? i would think maybe brake lines for the weakness but not vibration. i just hope its not the master cylinder or booster. i need this fixed before i get it inspected, thanks

JackG · #2 05-03-2008, 02:59 PM

Thats the foot massage....Standard on all pre turbo's

.

If your foot is going to the floor, That sounds more like
master cylinder. As for the foot massage, that does sound
like rotor. Check it out now, or have a mechanic look into
it.

Hatterasguy · #3 05-03-2008, 03:01 PM

Pull the wheels and see what the brakes look like.

jbach36 · #4 05-03-2008, 05:29 PM

You had a weird brake problem, and you continued to DRIVE this car until it got worse, and you have to practically stand on the pedal?????

jeff

sublakedesron · #5 05-03-2008, 05:49 PM

no it was not in use for a while about a month so i started it no probs whent down the driveway pressed the brakes didnt slow down. i had to push it to the floor to stop it and the pedal did this weird vibrate thing. so i turned right around and parked it again it has plenty of fluid no visible leaks (tomorow ill check again). but i am at work right now so cant take the wheels of to check. tomorow ill look into it more. (probably will spend the whole day to find out its some small thing)

Hatterasguy · #6 05-03-2008, 10:20 PM

When was the last time this car had a brake job?

Imiges of rotors worn down to their ribs and trashed calipers come to my mind.

Peter Kraft · #7 05-03-2008, 11:05 PM

Quote:

Originally Posted by jbach36

You had a weird brake problem, and you continued to DRIVE this car until it got worse, and you have to practically stand on the pedal?????

jeff

That's nothing, check out the thread where this guy wants to drive an unsafe and wrecked 300D several hundred miles......

http://www.peachparts.com/shopforum/showthread.php?t=221056

Matt L · #8 05-03-2008, 11:24 PM

Quote:

Originally Posted by Hatterasguy

When was the last time this car had a brake job?

Imiges of rotors worn down to their ribs and trashed calipers come to my mind.

I test drove a rough 300CD that must have had this problem. The owner was with me, and we drove the car about ten miles including some freeway driving.

Leaving, the brakes felt fine, but by the time we got back there was a tremendous chatter along with a pulsating pedal. I wasn't too afraid for my safety as I took it slow after this started; I know that three brakes will stop the car fairly effectively.

Needless to say, the seller was not in a great mood once we returned and I didn't buy the car.

tobybul · #9 05-04-2008, 01:56 AM

Am not clear on the symptoms you described. If you are saying that the pedal feels like there is no power brakes that you have to press harder to engage the brake, then I would say you are losing vacuum to the booster. You either have a vacuum leak in the booster line OR your vacuum pump is bad. This a serious safety issue and must be addressed asap.

If you mean that the pedal goes all the way down to the floor, it must be the master cylinder. Also, should be addressed asap if you intend to drive the car.

JackG · #10 05-04-2008, 08:17 AM

Quote:

Originally Posted by Hatterasguy

Imiges of rotors worn down to their ribs and trashed calipers come to my mind.

I had something like this happen right after I got my 84 D.
I did an emergency stop and heard a bang, then alot of grinding

.
I nursed the car home 2 miles and pulled the wheels. What I found was
a rotor that was worn uneven by the brake pads and probably
the lack there of.The rotor surface had actually snapped off
from the hub area. Never in my life had I seen a rotor worn down that
far.