A-class braking issue
#1
04-07-2006, 01:40 PM
A-class braking issue
I have an a 170 tdi.
Three or four times now i have pressed on the brake pedal only to find nothing happens. No pressure at all!
After pumping the pedal a number of times pressure seems to return to the braking system and the brakes work properly again.
The car has been serviced and MOT'd without any problems, and there is no leaking of brake fluids or anything cracked or broken with the entire braking system. It seems to be an intermittent fault, but a very worrying one at that.
Just wondering if any other owners have had a similar problem, or would know how to resolve this.
Thanks.
Three or four times now i have pressed on the brake pedal only to find nothing happens. No pressure at all!
After pumping the pedal a number of times pressure seems to return to the braking system and the brakes work properly again.
The car has been serviced and MOT'd without any problems, and there is no leaking of brake fluids or anything cracked or broken with the entire braking system. It seems to be an intermittent fault, but a very worrying one at that.
Just wondering if any other owners have had a similar problem, or would know how to resolve this.
Thanks.
#2
04-07-2006, 02:32 PM
RE: A-class braking issue
Hi,
From your symptoms I would suggest that you have a leaking master cylinder or possibly low brake fluid which has allowed air into the system.
When you press the brake fluid you squeeze the fluid in the system and the pressure is transferred to the slave cylinders in the brake calipers / drums. If there is air in the system the brakes feel spongey because air is compresible unlike brake fluid. However since you didn't state that the brakes were spongy, just that you had to pump, this suggests that pressure and fluid is leaking away i.e. you have to make another pump to secure the required pressure.
The leak to wjich I refer is internal so no fluid will be found on calipers, floor etc. The fluid leaks past a rubber seal when pressure (high) is applied. the seal acts like a piston ring in the engine.
The MOT confirms that the system has the capability to stop the car within the required distance etc and that all calipers and drums are working satisfactorily. The problem COULD NOT have been present when they happened to test the brakes.
Its unusual for the problem to come and go. Usually it just gets worse until it is rectified.
Are you sure that you are not just refering to the brakes becoming VERY heavy intermittently and you just happen to react by pumping the pedal which seems to make things better. If so then the brake booster, which provides assistance to make the brakes less heavy, may have a leaking diaphram or alternatively a leak in the vacumn supply system hose / non return valve to the booster.
Get a properly qualified individual / garage to get this problem sorted straight away.
Stuart
From your symptoms I would suggest that you have a leaking master cylinder or possibly low brake fluid which has allowed air into the system.
When you press the brake fluid you squeeze the fluid in the system and the pressure is transferred to the slave cylinders in the brake calipers / drums. If there is air in the system the brakes feel spongey because air is compresible unlike brake fluid. However since you didn't state that the brakes were spongy, just that you had to pump, this suggests that pressure and fluid is leaking away i.e. you have to make another pump to secure the required pressure.
The leak to wjich I refer is internal so no fluid will be found on calipers, floor etc. The fluid leaks past a rubber seal when pressure (high) is applied. the seal acts like a piston ring in the engine.
The MOT confirms that the system has the capability to stop the car within the required distance etc and that all calipers and drums are working satisfactorily. The problem COULD NOT have been present when they happened to test the brakes.
Its unusual for the problem to come and go. Usually it just gets worse until it is rectified.
Are you sure that you are not just refering to the brakes becoming VERY heavy intermittently and you just happen to react by pumping the pedal which seems to make things better. If so then the brake booster, which provides assistance to make the brakes less heavy, may have a leaking diaphram or alternatively a leak in the vacumn supply system hose / non return valve to the booster.
Get a properly qualified individual / garage to get this problem sorted straight away.
Stuart
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