Monday, February 20, 2012

Brake pedal firm when engine not running goes to floor after engine starts?

My brake pedal goes to the floor after starting the engine.
I have a nice firm brake pedal when the car is not running, as soon as Istart the engine, the pedal goes almost to floor.Brake pedal goes almost to the floor after engine starts.
Brake pedal goes to floor when engine on.
Brake pedal goes to the floor.
Brake pedal goes to floor only when engine running.
Brake Pedal goes right to floor when engine starts.

This types of queries are asked by many customers.
In this case the car is toyota Camry.It has ABS brake system.

But this types of problems are very common in ABS brake system cars.

In this case the brake is proper when engine is up,but as soon the engine is started the brake pedal goes to floor.
Holding the foot on the brake when engine is started the pedal goes to the floor .

On basis of this issue,the details to troubleshoot the problem is as follows :----
This types of problems basically occurs after replacing brake pads and brake shoes or if the brake pads and shoes worn out.
If this parts are replaced,but not installed properly,such problem will be noticed.
If you have solid pedal pressure with the engine off is unlikely any air in the hydraulic system. The ABS actuator assembly is not activated and the hydraulic circuits would be going through the actuator assembly and the wheel cylinders. Unless the abs actuator motor buzzes or has been activated is unlikely any air is trapped in the assembly itself. Sometimes well the engine is running if you overpower the brake pedal it can appear as though it is going down too far. If you're comfortable with putting in drive I would attempt to see if the brakes. Under normal conditions. All of this is assuming that you have all of the brake-shoes Springs and retainers installed correctly and adjusted correctly. If the brake drums and shoes are not adjusted correctly you can get over travel due to the vacuum booster applying excessive pressure that you normally would not get with the engine not running. This also is true for the front brake pads. Under vacuum booster pressure if the pads are not installed correctly it can cause a low or spongy pedal. You could remove all the wheels and see how much play you have in the rear brake shoes to drum travel and then have someone push the brake pedal to make sure that the calipers are not flexing or the brake pads are not moving excessively. This would be the only other possible solution.

If you are dealing your brake repair job yourself,then i recommend you to do it very properly.
I've had a lot of apprentices newbie's do four-wheel brake jobs with one wheel cylinder they bleed the brakes then get in and say I start the car and the pedal drops too far. A lot of this is due to over forcing the brake pedal and once the vehicle is driven they find that the stopping power is normal. Obviously you need to use caution when first starting to break this in. If the brakes start to wear in and are adjusted properly you should be able to stop with normal pressure without overpowering the brake pedal.

The low brake pedal  cab be the issue with the rear brakes out of adjustment or the front pads being stuck in the holders. 

This details will help you.

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