Rear caliper problem (Audi 80, B4)

Greavesy · 18-06-12, 04:42 PM

Afternoon all!

Can someone please help me!

I'm currently working on the brakes on my 1993 Audi 80.

Basically on the rear I've done:

New seals.
- Took out the piston, changed the dust cover seal and the seal between the piston/bore of the caliper.
New lines.
New discs.
New pads.
New fluid.

I've bled the system today and all of the brakes are working apart from the rear NS.

With the brake pedal pressed it is still possible to spin the disc. If you pull the handbrake with a bit of fight you can still move the disc.

I've tried the caliper on the OS and it still doesnt work so I know there isnt a problem with the lines.

With the caliper off the car, if I pull the lever for the handbrake it acts like a ratchet and pushes the piston out, though it doesnt return when let go? Meaning the piston gets further out everytime I pul the lever, this doesnt seem right to me??

I've tested the caliper, still attached the lines but using a block of wood instead of pads/disc. and the piston simply doesnt move.

Using a piston rewind tool the piston seems easy to move both in and out fairly easily so whats happening?

I hope this all makes sense and someone can point me in the right directon!

Regards,

Andy

shaun5 · 18-06-12, 05:41 PM

Have you completly removed the piston? There must be a thread that works the handbrake mechanism? is that stripped?

Greavesy · 18-06-12, 05:48 PM

yea I've took the piston out, the thread on both the piston and inside the caliper are fine. It's easy (relatively speaking to screw the piston on and off. I'm totally confused! . . . Just messaged someone on Ebay in sheffield who is breaking a cab, gonna try and get another caliper to test it out.

shaun5 · 18-06-12, 05:51 PM

Quote:

Originally Posted by Greavesy

yea I've took the piston out, the thread on both the piston and inside the caliper are fine. It's easy (relatively speaking to screw the piston on and off. I'm totally confused! . . . Just messaged someone on Ebay in sheffield who is breaking a cab, gonna try and get another caliper to test it out.

Well im stumped also. Ive got several spare calipers if you get stuck

Greavesy · 18-06-12, 05:53 PM

Nice one mate, thanks for taking the time to offer some adivce!
May take you up on that, how much would you want for one? PM me if you want.

Cheers,

Andy

BIGGYIN · 18-06-12, 05:58 PM

Don't know about the B4,but on my B2 you have to wind the pistons right back in.If you don't,the handbrake is weak.
It's something to do with the self adjusters,for the handbrake.
Don't know if it's the same,on yours?But worth,a try.

shaun5 · 18-06-12, 06:02 PM

Quote:

Originally Posted by BIGGYIN

Don't know about the B4,but on my B2 you have to wind the pistons right back in.If you don't,the handbrake is weak.
It's something to do with the self adjusters,for the handbrake.
Don't know if it's the same,on yours?But worth,a try.

I recon the B4's are pretty much the same then. Maybe try winding the piston back in with the tool whilst opperating the handbrake lever.

Greavesy · 18-06-12, 06:08 PM

I'll give you an answer shortly! Cheers!

yeti · 18-06-12, 06:15 PM

I had the same thing with mine, it wasn't bleeding up right. The only way I managed to do it i nthe end was take the caliper off, pre-fill it with brake fluid and bleed it with a none-return valve.

Greavesy · 18-06-12, 06:29 PM

Right, screwed the piston all the way back in, bled the system (as well as I could with my mum pressing the brake pedal), locked the bleed nipple off.

Now with the brake pedal pressed you can just see the piston moving, but it only moves a few mm before stopping again, its like its catching on something inside.
Like when you take a piston out using an air line, I was expecting the same thing to happen with the fluid - obviously I had a block of wood in the way to stop it firing onto next dorrs garden! lol

18-06-12, 05:58 PM	#6
BIGGYIN 4 ring whore! Classic Audi Club Member Join Date: Mar 2009 Location: Merseyside Posts: 7,976	Don't know about the B4,but on my B2 you have to wind the pistons right back in.If you don't,the handbrake is weak. It's something to do with the self adjusters,for the handbrake. Don't know if it's the same,on yours?But worth,a try. __________________ q90 B2 Type 85 - q90 B2 Type 85-PROJECT-ABY 20vt KARL. Injection is nice but I'd rather be blown

18-06-12, 06:15 PM	#9
yeti Senior Member Classic Audi Club Member Join Date: Oct 2009 Location: Derby Posts: 1,166	I had the same thing with mine, it wasn't bleeding up right. The only way I managed to do it i nthe end was take the caliper off, pre-fill it with brake fluid and bleed it with a none-return valve. __________________ 1990 Coupe Quattro (WTF did I buy that for?) Half a 1983 Coupe FI (long term parts shelf) 2003 Cors-arrrgh More Polos that you'd ever believe No time, no money, all the wrong tools and a workshop that's too far away

18-06-12, 05:41 PM	#2
shaun5 Grown up member Classic Audi Club Member Join Date: Dec 2011 Location: taunton Posts: 790	Have you completly removed the piston? There must be a thread that works the handbrake mechanism? is that stripped?

18-06-12, 05:48 PM	#3
Greavesy Grown up member Join Date: Apr 2012 Posts: 159	yea I've took the piston out, the thread on both the piston and inside the caliper are fine. It's easy (relatively speaking to screw the piston on and off. I'm totally confused! . . . Just messaged someone on Ebay in sheffield who is breaking a cab, gonna try and get another caliper to test it out.

18-06-12, 05:53 PM	#5
Greavesy Grown up member Join Date: Apr 2012 Posts: 159	Nice one mate, thanks for taking the time to offer some adivce! May take you up on that, how much would you want for one? PM me if you want. Cheers, Andy

18-06-12, 06:08 PM	#8
Greavesy Grown up member Join Date: Apr 2012 Posts: 159	I'll give you an answer shortly! Cheers!

18-06-12, 06:29 PM	#10
Greavesy Grown up member Join Date: Apr 2012 Posts: 159	Right, screwed the piston all the way back in, bled the system (as well as I could with my mum pressing the brake pedal), locked the bleed nipple off. Now with the brake pedal pressed you can just see the piston moving, but it only moves a few mm before stopping again, its like its catching on something inside. Like when you take a piston out using an air line, I was expecting the same thing to happen with the fluid - obviously I had a block of wood in the way to stop it firing onto next dorrs garden! lol