Brakes

[Jubby]

I seem to be loosing braking occasionally and for a split second only , but its worrying !

I have checked for leaks and have bled the system.

When the Engine is switched off the Brake pedal seems firm and gets firmer the more you press (as you'd expect). So I don't think the master Cylinder is faulty, But with the engine running the pedal is spongy and I can hear
a whoosh when I press the pedal as though air is getting in the system.

The Vacuum pipe is sucking ok, and the valve only operates one-way, and seems to seal quite well when the engine starts up.

I'm no expert but am thinking maybe the valve may be letting me down occasionaly (so I will replace it ). The vacuum pipe is new and quite heavy duty compared to the original so I don't think it is leaking.

As for the Servo , not quite sure how this works.

And I have ABS , but no warning lights appear

Has anyone had this problem ?

would like to get your views before I take it to a garage.

Thanks.

Jubby

[hobbit]

Does the system have a small bore pipe running fromt he servo to the bulkhead and dissapear into the dash area?

This is favourite for splitting away and causing some faults?

[Jubby]

Kev,

No ,   I've had problems with that one before though ;-)

It was removed along with the old 300TDI engine

Cheers,

Jubby

[driftwood]

could be a brake pad piston starting to stick, i had this problem i kept loosing the brakes, even changed the master cylinder. eventualy it stuck completely out and boiled the fluid, not shure though if the abs system would throw a fault though?


the servo i think should have a little check valve bung in it, you should only be able to blow through it 1 way.  fold a bit of paper and poke it into the servo housing, if its wet theres possibly a fault with the master. if youir peddle is stiff ( give it some welly and pump it ) with the engine off,  your servo/master may be ok.

[The Fat Controller]

check the correct way to bleed your system,some ABS systems do not "bleed" as old servo assisted systems do

[karloss]

When you lose the brakes, do you gain a noise like a pump running under the bonnet? It could be dodgy ABS sensors telling the system lies. The loss of brakes could well be your ABS coming in uninvited. Try disconecting the sensors, this will mean the fault light will be on but the brakes should then work as a non ABS set up.

To test the servo, pump the pedal with the engine off when it goes solid, keep your foot on and start the engine, the pedal should sink slowly down to a more "normal" braking position.

I'm assuming you've checked fluid levels etc?

[Jubby]

Thanks Lads,    I reckon it could be a seized Caliper  or a dodgy ABS Sensor,  I've had problems with both in the past !

Cheers,

Jubby