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Punto brake woes

Short Version:

Far too much travel on the brake pedal and the brake fluid seems to be full of air, almost looks like it's full of bloody fizzy lager not brake fluid. Help!

Long Version:

Got a 1999 MkI Punto 60, 94k miles, bought before Christmas, brake performance was unremarkably OK at the time. Got it serviced, they picked up leaking rear wheel cylinders, drums 90% worn, one shoe virtually down to the metal at one end with uneven wear (I think the centre pivot pin of the brake shoe had come out, certainly when I took the drums off the pivot pin and clip on the worn shoe was shiny and new).

So, did the shoes, the drums and the cylinders myself - all went on fairly unremarkably. Tried flushing and bleeding it with a pressure kit but the cap kept popping off the reservoir, so reverted to a one-way valve kit. But half the time the brake fluid seemed to be full of air still (bubbles seen through the clear pipe on the bleed kit) no matter how much I bled it. Anyway, did my best with it, drove it and the travel on the brake pedal was ridiculous, almost right the way down to the floor - although once the brakes bit the pedal seemed firm and the braking effective (considering it had new drums and shoes).

Jacked up each corner in turn and got someone to slowly depress the brake pedal while I spun each wheel in turn, to get an idea for when the brakes were starting to bite at each wheel. Front brakes were starting to bit with the pedal about 30% depressed, rears at 80% depressed. Handbrake was working as it should (starting to bite at 3 clicks, on tight by 4 clicks) so figured the rear self-adjusters must be working.

Wondered whether I could hear some air hissing down by the brake pedal on braking, and prior to that when bleeding, hoped it was nothing...

Thought maybe my (old) one-way valve kit was leaking, so bought a new one on eBay which arrived today. Planned to jack up each corner in turn, take the wheel off, and at rear check self-adjusters and cylinders, at front caliper slides working and pistons not seized, etc. and also rebleed each corner in turn with the new bleed kit. Only got as far as the rears, the self adjusters and the cylinders are fine however the brake fluid (seen through the clear pipe on the bleed kit) is still coming out looking like bloody fizzy lager even with the new bleed kit.

I'm a bit out of my depth on this one but my suspicion has to be that the brake master cylinder is buggered? :-(

Reply to
Vim Fuego
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Nope. It'd not introduce air into the system. You've either got a union that's not tightened up properly or a duff replacement cylinder.

Reply to
Conor

Conor wrote in news: snipped-for-privacy@news.karoo.co.uk:

This doesn't help with your problem but is worth doing whilst you're working on the rear brakes:

The Punto handbrake suffers from a seizing pivot on the lever that operates through the back of the drum. This causes the brake to bind and is probably the reason you had uneven wear in the first place. I had the same problem on our Seicento (same system). I'd strongly advise taking them out & giving them a good clean & grease 'while you're at it'. You'll need a couple of 3mm split pins to reconnect the handbrake cables afterwards.

Sorry it doesn't solve your present woes but it may well save you further trouble down the road.

Stu

Reply to
Stu

Er, don't think so. There's a bog standard handbrake cable that comes in through the backplate and engages on a handbrake arm on the trailing shoe. There's a number of braking system variants, even on this model alone there's a choice between Lockheed and Bendix.

Reply to
Vim Fuego

"Vim Fuego" wrote in news:WIyoh.50296$ snipped-for-privacy@newsfe3-gui.ntli.net:

Fair do's. One less job for you to do, then ;-)

Stu

Reply to
Stu

=============================== If you haven't already done so check the condition of flexible pipes - they don't last forever.

Cic.

Reply to
Cicero

Really? Do master cylinders not have any seals which keep the brake fluid and the air outside it separate? What about where whatever bit that's actuated by the pedal enters the cylinder?

I'm reasonably sure it can't be either the cylinder unions or the cylinders themselves (and that's the only bits that I've messed with) - could a leak at a union at a cylinder, or the cylinder itself, really be producing a steady stream of fizzy bubbles at the other cylinder, when that air is going to have to find its way all the way back to the master cylinder and then down the other leg of the diagonal split.

I suppose it could be another seal or union gone elsewhere in the system.

Reply to
Vim Fuego

I believe there was a recall relating to the brake pipes on this model year, if it's a mark 1. Recall was in early 2004 and treated corrosion IIRC.

Al

Reply to
Al Reynolds

There was indeed and it had the recall done and whatever checks were required were made, I've got the paperwork for it. Good thought though.

Reply to
Vim Fuego

Nope. Take the reservoir off and you're at the bit that's actuated by the pedal.

Sorry..I thought it was only on one.

Reply to
Conor

But where whatever it is that the pedal actuates enters the master cylinder....?

No, fizz at both cylinders.

By the way, the cylinders are not actually starting to move until the pedal is about 70% down - the travel is not in the brake shoes, but in the hydraulics. Which presumably trapped air would cause?

Is it possible/likely that there's actually no new air getting in, I've just got an absolute bitch of an airlock in the system, and if I keep bleeding and taking air out it will eventually clear the system of air? Although it feels like I've led the bastard to death already, must have run about a litre of brake fluid though it, easy.

Reply to
Vim Fuego

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