Brake Failure 300c

[KRAZYCLC]

has anybody not noticed brake pedal feedback from the abs when you slam on the brakes? i tried a few times and cannot get any feedback.also when the a/c/ is on the i have to apply more pressure to the brakes in order to stop. Anybody Else have these problems. The dealer said no "codes". "no trouble" I'm tired of this answer.

[II kings 9:20]

No, I get some mild pulsationas and noise. If your ABS failed then at full braking your brakes should lock up. Try this low speed in a parking lot preferably in the rain. At full braking, brake assist should apply 100% to the brakes even if you are not.

[Wayoflife]

I have had brake problems with my 300c from day 1 pulsating , noise ,caliper bolt falling out -- its been a nightmare and my local dealer tells me theres nothing wrong.

[joey]

Our ABS system does not pulsate like the older types. I find it hard to tell when the ABS is working. Sometimes my brakes make a grinding noise, which I think is the ABS.

[DZeckhausen]

Originally Posted by KRAZYCLC

has anybody not noticed brake pedal feedback from the abs when you slam on the brakes? i tried a few times and cannot get any feedback.also when the a/c/ is on the i have to apply more pressure to the brakes in order to stop. Anybody Else have these problems. The dealer said no "codes". "no trouble" I'm tired of this answer.

It's a common misconception that the pulsation felt in the brake pedal during ABS activation is the wheel locking and unlocking. This is not the case. The pulsation is the action of a pump that is returning fluid back to the master cylinder reservoir. This is called the accumulator pump and the accumulator is a temporary reservoir in the ABS control unit to hold fluid that is released from the caliper when ABS decides to lower brake pressure at that corner of the car. Some newer cars (including the 300C) have decidedly less ABS feedback than older cars. This is, in general, a good thing because many drivers who are new to ABS will become alarmed at the pedal feedback and prematurely let up on the brake pedal during an accident avoidance maneuver.

The processor in the ABS (and stability control) module spends almost 99 percent of its processing cycles performing self testing of the system. It's very likely that, if anything was really wrong with your ABS, the system would throw a trouble code and you would see a yellow or red light on your dash.

The relationship between AC being on or off and applying more pressure to the brakes is interesting. Are you noticing higher pedal effort only when the AC compressor is cycling or all the time the AC control is switched on? I could understand if the AC compressor cycling caused a momentary reduction in engine RPM and thus reduced vacuum to the brake booster. But there should be enough vacuum held in reserve that pedal pressure should be unaffected for a couple of brake applications. It's possible your brake booster vacuum check valve is defective. This can be tested at your shop.