Brake woes, front disc failure at low miles and other problems

[audifan]

Rear drums not discs. Well if you have fitted new drums and shoes and set the automatic adjusters correctly, then either a sticking or corroded slave cylinder or the hand brake is incorrectly adjusted or seized. Are the rear wheels free to turn when neither the foot brake nor hand brake are applied? If you have not already done so a complete brake fluid flush is recommended.

 

[Little Dog]

Rear drums not discs. Well if you have fitted new drums and shoes and set the automatic adjusters correctly, then either a sticking or corroded slave cylinder or the hand brake is incorrectly adjusted or seized. Are the rear wheels free to turn when neither the foot brake nor hand brake are applied? If you have not already done so a complete brake fluid flush is recommended.

Wheels rotate freely, new cylinders, new drums, new shoes, new solid pipes, all springs and mech joints good, new flexibles and fluid replaced.
I can only think of two more things to try, swop cylinders and see if problem moves, check for binding parking brake cable (newish done about 10k miles).
Perhaps I assembled the shoes wrongly, I’ll get pictures.

 

[audifan]

I would suspect either of the last two on your list. It is important that the tops of the shoes fit behind the stepped ends in the slave cylinders.
Here is a picture of the rear left side.

Not my picture. And this one showing the step in the piston and the shoe completely behind the step purely to highlight the step in the piston..

 

[Little Dog]

Thank you and yes @audifan they are assembled exactly like that with the shoe behind the lip on the cylinder. Got some swopping arround and investigating to do

 

[audifan]

On the back plate there are a few ( can't remember the quantity ) little white teflon pads that the inner edge of the shoes slide against. When worn they can cause the shoes to stick partially applied and prevent the shoe rocking too much.

No 3 in this picture

drum brake; back plate; wheel brake cylinder; brak... Audi A2 (A2) 2003 year Audi EUROPA 609020

drum brake<br/>back plate<br/>wheel brake cylinder<br/>brake shoe with lining Audi A2 (A2) 2003 year Audi EUROPA 609020 spare parts

audi.7zap.com

 

[Little Dog]

Thanks again @audifan, we are going to end up with a brake troubleshooting thread. Nylon pads were new a few years ago and are still in reasonable condition.

 

[kp 115]

On the back plate there are a few ( can't remember the quantity ) little white teflon pads that the inner edge of the shoes slide against. When worn they can cause the shoes to stick partially applied and prevent the shoe rocking too much.

No 3 in this picture

drum brake; back plate; wheel brake cylinder; brak... Audi A2 (A2) 2003 year Audi EUROPA 609020

drum brake<br/>back plate<br/>wheel brake cylinder<br/>brake shoe with lining Audi A2 (A2) 2003 year Audi EUROPA 609020 spare parts

audi.7zap.com

Hi Audifan,
12 required just bought mine today from TPS & 2 bungs for the backplates as well.
Keith.

 

[audifan]

Have you had a VCDS scan done, there may be a problem with the ABS. I would do a good brake bleed, making sure the reservoir never gets to the low level. Would also have the ABS pump reprimed using VCDS to flush out old fluid, debris or trapped air.

 

[Little Dog]

Have you had a VCDS scan done, there may be a problem with the ABS. I would do a good brake bleed, making sure the reservoir never gets to the low level. Would also have the ABS pump reprimed using VCDS to flush out old fluid, debris or trapped air.

My thoughts are now with the ABS. I always make sure no air gets into the ABS by making sure the main reservoir stays topped up. I cap off my ABS before working down stream. However one side of the car is connected via a m12? connector. Didn’t have them at the time so can’t remember how I capped it off. Perhaps I got air in on side??? Only have VCDS lite.

 

[kp 115]

I would suspect either of the last two on your list. It is important that the tops of the shoes fit behind the stepped ends in the slave cylinders.
Here is a picture of the rear left side.

View attachment 71965

Not my picture. And this one showing the shoe correctly behind the step....

View attachment 71966

Hi Audifan,
Is that really how the shoe should sit on the bottom photograph, mine sit like the top photograph behind the small lip & central to the cylinder piston.
Thanks
Keith

 

[audifan]

The bottom photograph is only to show the lip. It was done by rotating the piston and placing the shoe completely behind it. This is not how the brake runs in service just to highlight the step in the piston. When running the piston is rotated 180 so the step is outermost and the shoe sits behind the step in the piston as per the first photograph.

 

[kp 115]

The bottom photograph is only to show the lip. It was done by rotating the piston and placing the shoe completely behind it. This is not how the brake runs in service just to highlight the step in the piston. When running the piston is rotated 180 so the step is outermost and the shoe sits behind the step in the piston as per the first photograph.

Phew that’s a relief, I’ve also found the ATE alloy cylinders fitted last time have suffered wear to the lip to the point where it’s been pushed sideways so the piston tip is flat rather worryingly,
so I’ve gone for genuine VWAUDI cylinders.
Thanks
Keith

 

[audifan]

Thought the slaves were cast and not alloy? Or are you saying just the pistons are alloy?

 

[kp 115]

Thought the slaves were cast and not alloy? Or are you saying just the pistons are alloy?

The body of the wheel cylinders appears to be alloy

 

[Little Dog]

A2 cylinders should be alloy but they react with road salt and a thick layer of white corrosion builds up between the cylinder and back plate. It somehow jacks the cylinder up and when combined with worn nylon pads on the back plate the shoes come dangerously close to falling off the back of the cylinder pistons. Been there diagnosed it. Thread ruined by Photobucket but the words tell the story https://www.a2oc.net/community/index.php?threads/brake-shoe-position-on-brake-cylinder.32887/.
So I don't mind fitting the iron cylinders more commonly supplied in brake kits. My cylinders are iron supplied by Pagid, been using them for years.

 

[Little Dog]

Finally got a break in the weather and a chance to investigate the rear drums. The O/S is cooking itself:
- Both sides appear to be assembled correctly
- Both cylinders have the same bore
- The handbrake releases and the wheels spin freely
- gently apply the handbrake and both drums drag equally
- gently apply the foot brake and both wheels drag equally
- gently apply the foot brake with the engine running and the O/S drags more than the N/S
Possible ABS fault? Investigate with VCDS?

 

[audifan]

What do the drums look like. Try swapping the drums side for side to see if the problem then swaps sides. Drums could be slightly differently machined on one causing a taper. The shoes could also be uneven and time needed to bed them in. What size wheels and TYRES are you running on the rear?

 

[Little Dog]

Drums and shoes new ATE. Behaving exactly the same as Pagid that have been on for a few years. Wheels and tyres are std Audi SE.
Interestingly though I replaced the scorched ATE (needs a fresh coat of paint) with the Pagid that was braking cool. Been on a long run and the Padgid has not blistered its paint. More investigations tomorrow.

 

[audifan]

Is sounding like a drum issue. Picture of the inside of the drums may highlight an issue. An internal measurement while chucked on a lathe shows a host of different dimensions. Are both rears tyres exactly the same size?

 

[Little Dog]

Is sounding like a drum issue. Picture of the inside of the drums may highlight an issue. An internal measurement while chucked on a lathe shows a host of different dimensions. Are both rears tyres exactly the same size?

Only ever bought one size of tyre but I can swop sides to see what happens.