209MAD

I had a rude shock this morning when I started the car, pulled out of my parking lot, and drove all of 50meters and picking up speed and suddenly I lost all capability to brake! I was pushing the brake pedal right down to the metal, my dash lit up like a freakin Christmas tree, it was beeping the whole time, and the warning said DO NOT DRIVE VEHICLE or something like that. Good thing I didn’t panic and used my emergency brake coupled with Herculean strength on the brake pedal and the car rolled to a complete stop. I’m driving a 2004 SL500 equipped with SBC. Good thing too that I wasn’t on the freeway yet, and that my pregnant wife wasn’t with me. Has ANYONE experienced anything similar? I’m thinking of writing directly to Mercedes Benz, but I’m not even sure where or who to start with. Any info would be most appreciated. Honestly, I'm really scared to take the car out now...

mleskovar

Your car reverted to the backup system when SBC failed. Obviously, tow it to the dealer for them to look at it. Other early scary failures like yours prompted MB to scrutinize the system and several reliability technical changes and checks were made. Your dealer will make sure they were all implemented. The warranty for the main SBC pump was extended by MB as well. The campaign seems to have worked well as complaints about SBC failure have diminished on the forums.

209MAD

THank you so much for the info. Do you know if there was anykind of a recall letter that MB issued on this matter? Or that they have extended the warranty on the SBC pumps? I'm afraid my dealer might try to pull a fast one. Again, thanks!

vettdvr

There was a 10 yr extended warranty sent out by MB for the SBC brake assembly. I had the identical failure and situation. We parked the car and had it towed in. I will make sure my next car DOES NOT have the SBC system, and MB has dropped it from the car line up.

I HIGHLY RECOMMEND you have your car towed to the dealer for repairs.

I filed a report with the NTSB for total brake failure. This is the way the information gets out to make the vehicles you drive safer is by reporting serious conditions such as total brake failure.

mleskovar

I read there were several recalls sent out. MB is very sensitive to the SBC system because of the bad press. I"m surprised you didn't get any notifications from them. I'm guessing you aren't the original owner or you moved since you bought the car?

JonMBZ

I believe MB stopped using SBC entirely so you should be ok.

~CL500~

Glad you're OK and thankfully you were at the right place when this happened. So much for the so called "backup" system. If it reverts back to a standard vacuum assisted braking system (which is stated it should), it shouldn't have required that much effort for you to stop the vehicle.

As previous posters stated, the SBC is covered by an extended warranty. Get it fixed and file a report with the NTSB as vettdvr suggested. The point should be driven home every time this happens to an owner with SBC. That is just unaccepptable behavior for any car.

mleskovar

No vacuum assist in SBC brake backup. Just the old (tried and true) hydraulic cylinder that requires super effort to engage and only provides a small percentage of the normal force. The backup is totally inadequate to stop the car in a timely manner from speed. Someone estimated 3 times the normal distance to stop while under backup. If you have SBC you should know the drill if you get the failure....downshift the transmission and use the parking brake while standing on the brake pedal.

~CL500~

Wow! That's quite shocking that they would use non-vacuum as a backup. Thanks for the info mleskovar.

I can attest to how hard it is. My booster in the CL failed a while back and I was driving for a few weeks with no boost until the replacement came in. It was a workout to say the least, but I was used to it because I knew the problem was there. For this to happen suddenly can soil your drawers.

brakel8

Sorry to hear about your experience. Now as far as total failure of SBC, I've never seen it fail without adequet warning. The most common issue with SBC not functioning is low voltage, the vehicle will display consumers off line stage 1 or 2, if voltage gets too low then a red battery symbol and stop vehicle message appears, most drivers ignore this message (not saying you did). When the vehicle goes to the dealer for routine service the SBC gets checked for service life and if the threshold gets reached then the SBC pump needs to be replaced. MB extended the SBC warranty to 10yrs or 100K miles, most Benz's out of warranty never see a dealer again unless they get a recall and because of this the SBC never gets checked. The other way SBC fails to work is when someone jump starts the car and blows the pre fuse but this causes all kinds of other problems. I'm not a fan of SBC but when it's working it's amazing what it does! When you drive in the rain the brakes will apply for a split second every so many minutes to dry the brake rotors, in ABS application there is not brake pedal pulsation so it keeps the driver more calm and when going around a curve and brakes are applied in panic it knows to apply brakes only to the necessary wheels to prevent vehicle from loosing control. The bad is the horrible pump noise every 4 times the pedal is depressed. Almost forgot, have the dealer check the charging system because there was a campaign for bad voltage regulators.

vettdvr

Mine quit without warning. While driving in traffic the stop now warning came on in the FSS. We managed to get the car to the side of the road fortunately without hiting any cars. Absoultly no warning. Working now, then not working. The car was parked, towed and SBC system replaced.

Hopefully this doesn't happen again. But I really expect it to fail again. I filed a report on NTSB so they would have the safety record. Hopefully others will do the same and provide enough data for a safety recommendation on existing cars.