mot fail on brakes

[ger040 2]

my car has had an ongoing issue since i put it back on the road 

its initial mot it just about passed - just

The second mot it failed on rear brakes - i could not see anything wrong - but i changed the rear calipers and again fully bled

the system using a pumped pressure bleeder - i actually went through twice the amount of fluid it should have taken

i applied for mot again and the fault was still there but the inspector let it pass as he could see new discs, calipers and brake bias valve and 

said it must have a bit of air in the system, (he said on my car the front brakes do all the work anyway)

As we know there were no mots last year

Its coming around to new mot time again so its going to be an issue again

To me the brakes feel good all discs are all nice and shiny and pedal good 

To me the only thing left is the brake master cylinder - its still the original 

i have attached images its last mot fail sheet

[Dox 22]

Handbrake is not affected by the master cylinder and you have low effort on foot and hand braking.

 

brakes are diagonally split from the M/C, front right and rear left off one M/C circuit, front left rear right on the other. Again suggesting M/C is operating as it should.

what make we’re the rear disks and pads? Do the handbrake levers on the callipers return to there stops?

[ger040 2]

35 minutes ago, Dox said:

Handbrake is not affected by the master cylinder and you have low effort on foot and hand braking.

 

brakes are diagonally split from the M/C, front right and rear left off one M/C circuit, front left rear right on the other. Again suggesting M/C is operating as it should.

what make we’re the rear disks and pads? Do the handbrake levers on the callipers return to there stops?

The discs were genuine vw - a rare bargain on ebay.

i cant remember the pads but they would not have been a cheap budget brand - i dont go there.

i replaced the original rear calipers (mk2 type) with genuine vw mk3 calipers - came off a low mileage mk3 vr6 still have the gold paint. i later replaced these with refurbed items but made no difference

On a previous post i mentioned how my hand brake cables do not pull up square together within the tunnel  these were replacement gemco type specific type length for corrado and made no difference.

[Dox 22]

Do the levers on the callipers return to there stops?

[ger040 2]

19 minutes ago, Dox said:

Do the levers on the callipers return to there stops?

i will have to check this - can i ask what are the implications?

[fla 9]

20 minutes ago, Dox said:

Do the levers on the callipers return to there stops?

Might help to put return springs on the calipers if they don't go back to the stop position

[Dox 22]

11 minutes ago, ger040 said:

i will have to check this - can i ask what are the implications?

1, they need full movement and return to auto adjust for pad wear. 
 

2, linear movement of the cable goes to rotational movement of the levers affecting mechanical advantage.

 

once set up correctly I’d do some heavy braking to see if you can lock the rears, if not I’d adjust the compensator to give more rear effort, then deglaze the pads to give more bite - lightly used pads form a glaze that reduces initial bite on the disk

Edited July 24, 2021 by Dox

[ger040 2]

2 minutes ago, fla said:

Might help to put return springs on the calipers if they don't go back to the stop position

i always thought the mk3 calipers were a natural upgrade to the mk2 golf calipers with the return spring as eventually seize.

[Dox 22]

Daz alway washes whiter, each generation has improved but still have limitations

[Dox 22]

I’ve had this myself a few years ago and I ended up roughing the disks with a flap wheel in a grinder and de glazing the pads too - straight pass afterwards 

Edited July 24, 2021 by Dox

[ger040 2]

10 minutes ago, Dox said:

1, they need full movement and return to auto adjust for pad wear. 
 

2, linear movement of the cable goes to rotational movement of the levers affecting mechanical advantage.

 

once set up correctly I’d do some heavy braking to see if you can lock the rears, if not I’d adjust the compensator to give more rear effort, then deglaze the pads to give more bit - lightly used pads form a glaze that refuses initial bite on the disk

how do you adjust brake compensator valve - i thought there were set during manufacture

looking back and remembering when fitting the mk3 calipers i wound the calipers so the pads were just touching the discs prior to attaching the handbrake cables

[Dox 22]

The compensator is variable, preset with the weight of the car on its wheels. It’s attached to the shell via bracket and spring, the more weight  in the rear of the car the more force applied to the rear brakes.

you said it had been replaced? So factory settings are now disturbed.

I assemble the disks, pads, calipers with the pistons fully back, handbrake cables off. Then use the levers on the callipers to set them up, full strokes on the levers until the pads grab the disk. Then fit and adjust the cables.

[ger040 2]

Thanks Dox - i will give it a go and see how i get on 

[Dox 22]

It’s important that the brakes are working as they should before you adj the compensator.

If the car is non ABS or the ABS is showing a fault and you adjust the compensator to give excessive rear braking you’ll be sideways everywhere as soon as you touch the brakes.

 

if you’re unsure of the way it works, or unsure of your abilities take the car to someone who’s familiar with this set up.

[ger040 2]

no Dox i would not adjust the compensator unless i know what i am doing 

ABS works fine 

[dragon green 4]

Mine would not bleed through the o/s/r, I had to get the abs pump reconditioned, it didn’t show any fault codes either !

[ger040 2]

I have had a look at this again to day - completely stripped the rear calipers, carriers discs etc and reassembled same 

and the problem is still there

adjusted the calipers so there was a bit of resistance of the brake pads on the discs rotating by hand 

as soon as i apply the hand brake the drivers side has more play hence the difference.

using a spanner and pulling down on the handbrake lever on the calipers the passenger side moves about 5mm before pads engage - the drivers side has to be double this

i have bled and bled these brakes using a pressure bleeder

 

 

[dragon green 4]

The handbrake mechanism has nothing to do with the hydraulic system !
Try adjusting the “loose” handbrake cable at the handbrake end to make the movement equal

[ger040 2]

22 minutes ago, dragon green said:

The handbrake mechanism has nothing to do with the hydraulic system !
Try adjusting the “loose” handbrake cable at the handbrake end to make the movement equal

Thanks for the reply Dragon Green

Maybe i am being stupid here but with the handbrake not being equal (not pulling up square on both sides) surely this in turn puts the foot brake operation out too.

i.e one side will be better than the other

Jesus my mk2 16v was simple compared to this

[1xshaunx1 27]

The handbrake works mechanically via the leavers and such, if you’ve checked by hand on the levers and they operate differently the fault with the handbrake is in the callipers. This is why I needed new/ refurbed callipers and went for new Mk 4, a link in my thread. The drivers one did next to nothing as much as I try. With the new ones all was well I also put new cables on while I was at it. 

[ger040 2]

1 hour ago, 1xshaunx1 said:

The handbrake works mechanically via the leavers and such, if you’ve checked by hand on the levers and they operate differently the fault with the handbrake is in the callipers. This is why I needed new/ refurbed callipers and went for new Mk 4, a link in my thread. The drivers one did next to nothing as much as I try. With the new ones all was well I also put new cables on while I was at it. 

Thanks Shaun 

This has baffled me to be honest - these were a new / refurbed set of calipers which replaced a set of mk3 vr6 low mileage callipers with the same problem

The handbrake cables are new also

Could it be air in the system?

[dragon green 4]

I’ve had 3 sets of (new) calipers on mine, they are not as good as people make out !
Get a mate to help, crack the flexi hose half a turn on the offending caliper. Get your mate/help to depress the brake pedal, are you getting fluid ?
I know you were with the pressure bleeding, but we need to know, is the cylinder/ABS unit working properly

[ger040 2]

1 hour ago, dragon green said:

I’ve had 3 sets of (new) calipers on mine, they are not as good as people make out !
Get a mate to help, crack the flexi hose half a turn on the offending caliper. Get your mate/help to depress the brake pedal, are you getting fluid ?
I know you were with the pressure bleeding, but we need to know, is the cylinder/ABS unit working properly

i will give it a go - will be a day or two

[ger040 2]

On 8/7/2021 at 7:42 PM, dragon green said:

I’ve had 3 sets of (new) calipers on mine, they are not as good as people make out !
Get a mate to help, crack the flexi hose half a turn on the offending caliper. Get your mate/help to depress the brake pedal, are you getting fluid ?
I know you were with the pressure bleeding, but we need to know, is the cylinder/ABS unit working properly

Hello Dragon Green 

Got back to this broke the rear flexis where they connect to the calipers and pressing the brake pedal there is fluid at both calipers

[dragon green 4]

The fault must be in the calipers !
Hard to believe as you’ve changed them