C3 binding brakes

Ringmaster · 04-06-23, 11:47 AM

Hello folks,

Was happily tootling along in my C3 yesterday. Braked at T junction and heard a loud click come from the area behind the instrument cluster. Afterwards the car seemed to be sluggish. Speed didn't relate to engine revs. The brake pedal felt very firm at times. Carried on home and heard another click. Car surged forward as though liberated from some invisible force. Braked again and the car became sluggish. Splashed some water over all 4 wheels and they were steaming hot.

Me thinks I have a faulty brake booster rather than a faulty master cylinder.

Opinions, please....

Ringmaster · 23-05-24, 08:56 AM

Turns out my brake master cylinder was corroding within. Where it meets the brake booster was full of aluminium powder which must have been clogging the mechanism and causing the binding intermittently.

A good clean and new master cylinder solved issue!

ovalking · 23-05-24, 10:26 AM

Glad you found a problem and hope the solution is long lasting.

Were there any external clues?

Mine seems to be working fine. But I'm changing some flexi hoses at the moment, and brakes are on my mind...

Ringmaster · 23-05-24, 11:13 AM

There were no external clues. Looking back, as all 4 wheels were affected, we should have immediately looked at the master cylinder rather than wasting time flushing the brake fluid.

There is a gasket between the M/cylinder and brake booster. That had perished causing aluminium to contact the steel of the booster, which probably triggered the corrosion.

23-05-24, 08:56 AM	#2
Ringmaster Senior Member Classic Audi Club Member Join Date: Apr 2008 Posts: 1,335	Turns out my brake master cylinder was corroding within. Where it meets the brake booster was full of aluminium powder which must have been clogging the mechanism and causing the binding intermittently. A good clean and new master cylinder solved issue!

23-05-24, 10:26 AM	#3
ovalking Grown up member Classic Audi Club Member Join Date: May 2009 Location: Ipswich Posts: 271	Glad you found a problem and hope the solution is long lasting. Were there any external clues? Mine seems to be working fine. But I'm changing some flexi hoses at the moment, and brakes are on my mind...

23-05-24, 11:13 AM	#4
Ringmaster Senior Member Classic Audi Club Member Join Date: Apr 2008 Posts: 1,335	There were no external clues. Looking back, as all 4 wheels were affected, we should have immediately looked at the master cylinder rather than wasting time flushing the brake fluid. There is a gasket between the M/cylinder and brake booster. That had perished causing aluminium to contact the steel of the booster, which probably triggered the corrosion.