Brake Jamming

[mike2020]

I have a problem with my brake pedal when pushed hard, it pushes back up at me????

[jonlabree]

Take the brake test at Reatta.net and then report the results.

[Jim]

One of the tests is to step on the brake pedal several times is rapid succession and see when the red light comes on. It should come on in about 6-7 pumps with a very good accumulator. If it comes on at about 3-4 pumps that is OK if it comes on in one or two pumps your accumulator is shot and your pump/motor is working many times harder than it is supposed to and will soon wear out.

Finding a good used accumulator is almost impossible. I recently bought about 25 of them in junk yards and only one was a 3-4 pumper. The rest went in the garbage.

New from GM is about the only way to go and they are about $ 140. I do have good used pump/motors and pressure switches.

I can be reached at jfinn@cpinternet.com

[Richard S]

Not sure about the Teves, but on the Bosch system used on the Allante, the subtle "kickback" is usually the precurser to the "rockhard" pedal which means catastrophic brake failure. That is, you can jam on the pedal so your back is impressed into the seatback and still not be able to depress the pedal enough to engage the brakes. Someone once opined that some internal valve might fail in such a way that you are actually fighting the pressurized assist rather than being helped by it. I don't know if that comports with any mechanical possiblity within the Teves system or not.

[Guest Greg Ross]

Mike2020,

You really need to heed what's being recommended to you. Absolutely, do the test. The few reports that have come back here from Owners' experience with this failure is frightening, ther've been some accidents that were most likely a result of this failure.

As you'll see if you research "Teves" issues on this website you'll come up with the recommendation to do the test, change the accumulator at the first sign of deterioration and to "Flush your Brake System" at least every couple of years.

[bobwhite]

There's nothing like a hard brake pedal during an emergency stop to sharpen ones senses. I used to have a hard brake pedal once every month or two. I started having the brake system flushed once a year, and haven't had a problem since. I have changed the accumulator once. I do the brake test twice a year. It has been five years since I started doing this and I haven't had a single hint of trouble with the brakes.

[Guest tomt]

Right on, and people here are adept at reading the results that you get. Teves has been a great system for me, but people here know more than any mechanic you will find.

The good mechanics I have found read what is written here and fix the problem correctly. Of course you can always do it yourself.

[mike2020]

How does the accumulator work? What wears out in them?

[bobwhite]

The accumulator is a energy storing device. It saves enough energy to allow for a limited number of stops if the brake pump fails. My Citroen uses them for braking, as well as suspension. The heavy metal globe has a bladder in the middle, (see illustration). One side has brake fluid, the other is pressurized with nitrogen.

The pump forces the nitrogen to compress, thus storing energy. When needed, the pressurized accumulator acts as a temporary replacement for the pump. As the bladder ages, it develops leaks that allow the nitrogen to escape. Eventually it is all gone and the pump comes on immediately when you depress the brake pedal. This system is also used on large airplanes, but gets more complicated. See picture of 737.