was cruising in DC with the air condition blowing..then all of a sudden, approaching a light, my brakes completely failed...I stepped on it to the floor with no response..I pumped it to get some braking...just managed to stop. Switched the air off and drove cautiosly for the next three lights with the same loss of braking. I kept pumping even when I did not need the brake..and will get some braking.....well, all of a sudden, the brake starts working normally....of couse this was so darn scary for me...I am taking it in this week.
Anyone experienced anything like this?
what could possibly be the cause?


thanks guys

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"Paps was right. Wish I had listened."

Faulty master cylinder? Don't drive it like that.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

thanks a lot buddy....

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"Paps was right. Wish I had listened."

89 300E 200K miles:
Driving to the mall today, stopped by the pharmacy and backing out I tapped the brakes and they seemed to pump up a bit. OK, I'm thinking that's how you adjust them and I hadn't done that before. The brakes acted totally normal until I was exiting the freeway and they nearly went to the floor. My stomach went to my throat. I pumped them a little and got pedal back. Same thing at the next light but I was going really slow and trying to stay way back from any cars. Thank goodness I was only 1 light from the store and I pulled it into the back of the parking lot so I could call AAA. It also pulled a little to the left when it did stop. The AAA guy said it could be a bubble but I am not driving that thing until they find the problem!

My husband's Dodge Ram diesel truck had brake failure with only 10K miles on it while we were hauling our horse trailer in Wrightwood a few years ago. We have a big gooseneck with living quarters so it carries alot of weight. We were on a winding dirt road going down into a ranch with the mountain on one side and a sheer drop-off on the other. Unfortuntely we hit our friends in front of us knocking their horses down in their trailer and smashing their trailer into their new Dodge truck and cabover camper. I have never forgotten the terror of rolling down that road and finally coming to a stop. It was the master cylinder on the truck but we had to fight Dodge corporate over it because their 'special master' said it was worn brake pads in the front. Our local Dodge dealer's brake guy finally got involved and Dodge had to admit it was the MC and paid for all the repairs to our truck and our friend's damage. They also replaced the whole braking system because I wasn't about to get in that truck again.

WOW!!!! that is one scary thingy..perhaps it's time for a brand new car

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"Paps was right. Wish I had listened."

Well, I love my car and don't want to sell it. Forgot to add, the brake fluid was full and didn't see anything leaking underneath. AAA towed it to my mechanic but they can't get to it until Tuesday. I think I'll have the master cylinder replaced no matter what they find.

Are either of you using brake dust shields? Several years ago I was using the dust shields in my 92 400E and the brakes failed much like you described. They started working again in a few minutes after things cooled down a bit. It was a hot day and I had just been driving pretty agressively to rush across town in heavy stop and go traffic to get to a store before they closed.

My shop pulled off the dust shields and changed the fluid. Brake fluid absorbs moisture and the brake dust shields reduce the brakes ability to cool. That combination caused my brake fluid to boil inside the calipers. I've since had many many happy miles with no further strange brake problems.

I won't use the dust shields and I get my brake fluid changed every couple of years now...

Good luck!

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02 S500
92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)

This is a mastercylinder failure.
It happened to me pulling into Walmart. Luckily I was on a grade and was able to stop. After a failure the system is pretty resiliant because it gives you enough brake pressure to get you to your mechanic, driving cautiously of course. The suddeness of the pedal to the floor really puts the fear into you!