Astra 1.7 TD '98 - Brake pedal creep

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Thu 2 Nov 2006 13:03
Astra 1.7 TD '98 - Brake pedal creep - Cornish Lass
Recently noticed when stopped in traffic, particularly facing downhill, my brake pedal slowly creeps down to the floor. I know its not really good practice to sit with footbrake on and not use handbrake, but who doesn't?

Checked fluid levels several times in last 2 weeks and doesn't seem to be losing any and no sign of any obvious "damp" patches around wheel cylinders. I'm not sure if this is a new development, or I've just not noticed it before. I did a quick "google" and found info on a phenomenon known as "diesel brake creep" which is unique to the diesel set-up. Could it be this?

Don' t really want to book in for work if its not necessary. Is there a foolproof method I can use to check if its normal or something more sinister???

Thanks in advance, L
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Thu 2 Nov 2006 13:27
Astra 1.7 TD '98 - Brake pedal creep - DP
The only difference AFAIK between petrol and diesel cars when it comes to brakes is the method of providing the servo assistance. On a petrol engine, the inlet vacuum is used, but a diesel engine has no inlet vacuum, so a separate vacuum pump has to be used.

It sounds like you have a master cylinder fault to me. Get it checked out ASAP.

Cheers
DP
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Thu 2 Nov 2006 16:26
Astra 1.7 TD '98 - Brake pedal creep - Ruperts Trooper
A number of Vauxhalls, including the Mk4 Astra like yours, can suffer "damage" to the master cylinder seals when new brake pads are fitted. If the caliper pistons are pushed back too vigorously the hydraulic fluid inverts the master cylinder seals as it goes back into the master cylinder.

I've never heard of diesel brake creep, as DP says the braking systems are identical apart from the method of generating vacuum.

Get it checked, pronto.
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Thu 2 Nov 2006 17:02
Astra 1.7 TD '98 - Brake pedal creep - MW
95% chance it is a failed master cylinder
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Thu 2 Nov 2006 17:16
Astra 1.7 TD '98 - Brake pedal creep - Number_Cruncher
found info on a phenomenon known as "diesel brake creep"


I've had a quick nosy at this, and I find the explanation given is nonsense.

The maximum pressure drop across a servo is atmospheric, (no matter how hard you suck, you can't produce negative absolute pressure) whether this vacuum is produced by the engine or a pump, it doesn't matter.

I concurr with the advice given above - have a competent garage check the system thoroughly, rectifying the fault, before using the car again.

Number_Cruncher
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