Not sure if this has been covered before but new to this forum. Have just done a rebuild on a 3door Cosworth for my boss and having an issue with the brake system, all seems fine with pump,wheel speed sensors etc but when you press the pedal the ABS seems to be kicking back up the pedal and it is refilling the master cylinder with fluid as if something is blocked and not letting the pressure out. Car past the brake test in MoT but failed as when this problem occurs the abs light and red brake warning light come on, they go out again when pump has built up pressure again.

Thanks in advance for any help

 

Replied to your other thread, although you give a little more info here.

It sounds like a hydraulic problem (i.e. possibly a faulty M/C) this would cause both lights to come on due to low pressure, hence it's ok until you depress the pedal.

It sounds like it's activating the ABS, which in theory should only be done via a discrepancy in wheel speed.

Martin

 

Thanks Martin, managed to get a S/H master cylinder and pump assembly fitted it this morning but pump just running constantly and not building pressure, has been lying so assume the accumulator maybe faulty.

 

yes, the pump is not the issue. The accumulators I have heard can be rebuilt, although difficult as they are filled with nitrogen, iirc.

Does the sphere shows signs of leakage?

Martin

 

Relay issues

 

No signs of leaking. Have built everything back up as it was as before I changed to the sh master cylinder and pump it was building and maintaining pressure ok. Relays all seem to be working ok. It's a strange problem. I've nearly exhausted all options.

 

Just a wee update, have refitted the original master cylinder and pump this morning, there seems to be some sort of pressure switch on the actual master cylinder, held in with a circlip, for some reason it doesn't seem to be activating to allow the accumulator pressure out and I assume that's why it's back feeding into the brake fluid Reservoir.

 

Just a wee update, have refitted the original master cylinder and pump this morning, there seems to be some sort of pressure switch on the actual master cylinder, held in with a circlip, for some reason it doesn't seem to be activating to allow the accumulator pressure out and I assume that's why it's back feeding into the brake fluid Reservoir.