Major Brake Issues after Caliper / Pad / Disk Change

[garyjwilson]

Ok guys

Had an issue with dragging brakes.
Put the car on ramps to properly check out and the culprit was the nearside front caliper. Managed to free the caliper but the problem came back 2 minutes later.
Whilst replacing the caliper I decided to change the front pads also. Upon removal found that the inner pad had worn away completely despite there being 5mm left on the outer pad. This had happened both sides and completely knackered the disks !!!
Back to motor factors and new disks and pads duly fitted as well as the new caliper.
Spent 2 hours with my friend bleeding and re bleeding the brakes using the convential method but I can not get the brake pedal to stay firm. The brakes work but only after pushing the pedal half way down do they begin to engage..after searching I have read various posts relating to the servo (brake booster) master cylinder and ABS pump....This is now driving me nuts....With the engine off a couple of pushes on the brake pedal gets it rock hard and it maintains the pressure. As soon as the engine is switched on however the pedal simply pushes right down. and as previously stated the brakes do not begin to engage until the pedal is depressed over half way.
Can anyone advise the best course of action now...
(By the way...no fault codes are present now)

Thanks
Gary

 

[vwztips]

On occasion I have had to go into the ABS module with Vag-Com and activate the pump through the Test procedure to get the pedal back.

 

[Mikey2]

Uneven pad wear stems from improperly installed tensioner spring. The spring ends should be installed first and then force the spring behind the lugs in the caliper retainer.

Your current problem may result from air intrusion into the ABS unit (=fluid level has instantaneously dropped too low while bleeding). This can be rectified by using the VAGCOM, as stated.

If the a.m. does not cure the problem, then there might be a leak inside the master cylinder. When bleeding the brakes, one is able to push the pedal all the way down and at the same the master piston protrudes deeper than in normal use. In an older car, there may well be dirt accumulation inside the master cylinder which disrupts the piston seal. This should, however, be seen as a slow pedal travel while keeping the pedal pressed and with the engine stalled.

 

[aja8888]

Make sure the caliper slider bolts are greased with the proper lubricant. Sticking sliders can cause uneven pad wear also.

 

[garyjwilson]

I have been driving the car since the calliper pads and disks were changed. Over the days the pedal seemed to be getting higher and was seemingly returning to normal. Today however the the pedal has risen to its highest point and the slightest touch activates the brakes. In addition I have checked and the brakes are dragging again........If I mess with the brakes whilst parked...fully depressing the pedal as much as possible with engine running and then doing the same whilst the engine is off, when I then restart the engine normally the pedal has reverted back to requiring depressing a couple of inches before the brakes engage. The brakes are still dragging however and the after a while the pedal will rise to its highest point and the brakes are hyper sensitive again....
Once again thanks in advance for any help.

 

[Mikey2]

Your brake booster is defective.

 

[vwztips]

Exact same thing happened to mine about 6 weeks ago. Could not determine if it was master cylinder or brake booster. Decided to replace both at same time as it is a lot of work if you replace one and it turns out to be the other. I had a used master cylinder and brake booster but of course VW used 2 different master cylinders and the one I had did not match what was in my car. The main difference is where the ports are for the brake lines. Got mine from a junk yard and replaced both pieces as a set. It is a pain to replace and also to bleed. I have a pressure bleeder and it still took 3-4 times per wheel to get all the air out, then had to run through ABS/pump test to get good pedal. Everything is all good now.

Check your master cylinder to see which one you have. It will be stamped on the side. IIRC ATE and Lucas are the same. I see you are in Liverpool. If you have not dealt with them before call the guys at Volksmine. They are good to deal with.

 

[TDI321]

Also... when caliper is removed from car but still on the rubber hose. Get the pistons to come out (not the whole way or its a real mess) and use a tooth brush and brake fluid to scrub and clean the outside Diameter of the pistons. If they are dirty and have ridges built up then they wont retract correctly and will be soft. My guess is they are sticking there. I’d do this before buying expensive parts.