Brakes - bit of a problem...

[Welly]

OK, can anyone give me any ideas as to what is going on here...

My brakes after driving for some time earlier on decided that they were going to stick on. Both front wheels were stuck on to the point the engine couldn't turn them eventually... The brake pedal is also completely solid even with the engine running.

It got progressively harder over a period of a few miles.

New master cylinder has been fitted, one from a TT, however they have the same part number on both VAG CAT and also ECP stock the same part for both the TT and S3.

Basically, I'm baffled. Never, ever, had this problem before.

Discs and pads are wrecked.

Any ideas??

 

[Welly]

PS. To get it home I had to crack off the bleed nipples on both front callipers and release some of the pressure.

 

[<tuffty/>]

Was it a new MC or a used MC? Can't remember what it was you told me you were gonna buy in the end...

Can't think of anything obvious tbh mate, only time I have had experience of this was on my old Mk2 Escort when the servo piston rod (which had a screw in end for adjustment) came loose and wound itself undone and while not completely locking the brakes they did start to bind...

Hope you get it sorted but if you used a second hand MC then maybe it was a bit dodge... there should be a return spring internally to the MC, maybe its that giving probs? clutching at straws a bit here mate but (and I know you won't wanna hear it) maybe you should have gone for a new one from GSF for 40 quid more than the ebay one you showed me (assuming thats the one you went for)

<tuffty/>

 

[Dane]

I have the discs for the pads in the box that I lent you dude, might help.

 

[Westy]

You're not having much luck recently Welly. Hope you get it all sorted soon mate.

 

[Y83OLK]

Had this on couple mk4 platforms, usually a faulty master cylinder.
.. Did have it on a a4 where the servo was split/ filled with water and the water froze putting the brakes on.
But i doubt your anywhere cold enough for that.

 

[aragorn]

Not really much it can be other than the MC.

When the pistons move back to the "rest" position, the fluid ports to the reservoir are uncovered meaning the line to the caliper is at atmospheric pressure. For pressure to remain in the line (ie the pressure that was holding the brakes on) the pistons in the MC couldnt have been fully returning.

You can see what i mean here:

When the pistons are fully retracted there would be no way for pressure to remain in the line.

I guess the only other possibility would be some part of the pedal/linkage holding the brakes on...

 

[Welly]

Mwah ha ha.

I have found the problem....

Spot the issue below:

Welly's helpful hint of the day.... S3 and TT MCs are NOT the same....

My new motto should be 'F**king things up, so you don't have to.....'

S3 one fitted again for now, needs bleeding tomorrow again.

However now = bed. Toodles.

 

[Sam_]

I guess you'll be checking old vs new parts side by side now That must have been a very annoying refit

 

[Westy]

We live and learn mate. You seem to be doing a lot of learning recently though

 

[jojo]

I guess you'll be checking old vs new parts side by side now That must have been a very annoying refit

I always do this first, you just never know....

 

[Sam_]

I did it with my Haldex the other day, just in case! I thought, knowing my luck and the car being Australian it'll be different...

 

[JS1500]

Glad you found the issue Welly.
What new discs and pads are you going for?

 

[Welly]

I guess you'll be checking old vs new parts side by side now

Annoyingly, I did this to a degree. I measured the rod length on both and tested that both rod lengths were the same - which they are.

The problem was the bellow that the rod comes out of.... It's MASSIVE by comparison....

 

[Sam_]

If it makes you feel any better; I'm sure I've done similar in my time