My car is in a garage having new rear calipers fitted. Garage just called me to say it's done but that the brake pedal is good with the engine off, but with the engine running it goes down a long way before the brakes bite. Before it went in I told them not to bleed the brakes the old fashioned way (pumping the pedal) because I remembered reading about problems with it on here. Just had a phone call to say they have bled the brakes with a pressure bleeder and the pedal method (argh!). Really hoping they haven't damaged the MC!

 

Given what I have does anyone know if the MC is likely to be damaged and how to tell, or if not then how to rectify the crap pedal?

 

About to go to the garage now and see what's what...

Edited 15 September, 20169 yr by vrsTom

Sorry to bump an old-ish thread...

 

My car is in a garage having new rear calipers fitted. Garage just called me to say it's done but that the brake pedal is good with the engine off, but with the engine running it goes down a long way before the brakes bite. Before it went in I told them not to bleed the brakes the old fashioned way (pumping the pedal) because I remembered reading about problems with it on here. Just had a phone call to say they have bled the brakes with a pressure bleeder and the pedal method (argh!). Really hoping they haven't damaged the MC!

 

Given what I have does anyone know if the MC is likely to be damaged and how to tell, or if not then how to rectify the crap pedal?

 

About to go to the garage now and see what's what...

Its way more likely that they've pumped air into the ABS valve block, in which case you need a VAG computer (dealer, specialist or VCDS) to get it back out! It's their problem to fix, but if you can tell them "it's probably $this, so try $that, and if that doesn't work then it's likely you've FUBAR the master cylinder"...

Cheers - do you know if VCDS lite can do it?

Update - NSF and OSR brakes have low braking force. Other 2 wheels are good. Handbrake is good on both wheels.

Bled NSF and OSR again and pedal is still crap.

Air in ABS unit do we think?!

Sounds like it.

However if using a pressure bleeder (which is best) it must be set to under 1 bar. Any more and the air will not clear from the EDL line in the ABS unit.

Cheers Tech1e. Pressure bleeder was on 10psi or 0.68 bar but the pedal is still crap. The garage I'm in doesn't have full VAG diagnostic kit so I guess taking it elsewhere is going to be the next step.

Another thing maybe you can answer - should the brakes be bled with or without the engine running? So far they've been doing it with the engine off.

Edited 24 August, 20169 yr by vrsTom

Garage thinks it's air in the master cylinder or faulty master cylinder. If this was the case wouldn't the brakes be weak on all wheels?!

 

They also said that there's no bleed nipple on the master cylinder and there should be. Is that right? The master cylinder has not been replaced in my ownership (5 years and 80k miles).

Edited 24 August, 20169 yr by vrsTom

Some do have a bleed nipple but most don't, to bleed the cylinder just crack off a pipe if needs be.

Update - NSF and OSR brakes have low braking force. Other 2 wheels are good. Handbrake is good on both wheels.

Sounds like air in that circuit, since the car uses a "X-split" on the foundation hydraulic circuits (although it does modulate each wheel individually when the ABS activates).

 

Other thought; is there any sign of one of those 2 lines ballooning when the brakes are applied? (needs 2 people and preferably a hoist.

Sounds like air in that circuit, since the car uses a "X-split" on the foundation hydraulic circuits (although it does modulate each wheel individually when the ABS activates).

 

Other thought; is there any sign of one of those 2 lines ballooning when the brakes are applied? (needs 2 people and preferably a hoist.

 

That was my thinking too. Do you think the master cylinder can be ruled out?

 

Don't think there is any ballooning as the pedal was fine before going in for this work and with the engine running the pedal is very low - not just spongy. Will try and get that checked out as well though.

 

Does anyone know if VCDS Lite can bleed the ABS unit and whether they should be bled with or without the engine running?

Edited 25 August, 20169 yr by vrsTom

Garage are reluctant to spend any more time on it as it could be wasted time if it will need diagnostics anyway. On the plus side they said they will only charge the labour for the other work they did (discs, pads and calipers).

 

Now leaves me with the problem of finding somewhere else competent enough to do it, getting the car there and knowing how much it will cost. Do I risk a dealer or another independent?!

 

Surely it shouldn't be this difficult to bleed the brakes on a car which is very similar underneath to a Golf/Leon/A3!

sounds like you need to find a local body with vag com. id be a bit peed at the garage just not wanting to try anymore. seems weird. 

sounds like you need to find a local body with vag com. id be a bit peed at the garage just not wanting to try anymore. seems weird. 

 

I have VCDS Lite but not sure if it can do it. The next thing they wanted to try was removing/replacing the master cylinder - potentially a waste of everyone's time & money if it turns out it's not that (and seems unlikely to me as the MC was fine before).

i had a issue bleeding mine pedal was bad but i had to bleed the master cylinder all good. has that been tried

i had a issue bleeding mine pedal was bad but i had to bleed the master cylinder all good. has that been tried

 

Not yet but I did suggest it to the garage. Decided to cut my losses with them now and take it elsewhere.

mine has 2 bleed nipples you can quite clearly see them. be worth that first 

The garage seem reluctant to try bleeding the master cylinder (mine doesn't have bleed nipples).

 

Anyone care to comment on the chances of the master cylinder having failed? Brakes were previously fine and passed an MOT only 2 months ago.

I doubt it's knackered but a good bleed will probably sort it.

Update...

 

Had the car recovered home as it would've been a bit dodgy driving it.

Took the car to a local garage who fixed it by bleeding air from the master cylinder. Brakes now bite right at the top of the pedal and feel much better than before - probably due to having crappy Apec front pads previously (fitted before I bought the car!) and the new rear calipers. Now have Pagid discs & pads all round and new (green!) rear calipers.

 

It seems that the other garage (a Saab "specialist" in Stevenage) most likely introduced air into the master cylinder. They told me it didn't have bleed screws which is complete rubbish as I have now seen them clearly myself from the top of the engine bay, so they were either lying about the supposed lack of bleed screws or are unbelievably stupid. The only reason I can think of that they'd lie about the bleed screws would be a fraudulent attempt to charge me for an unnecessary replacement of the master cylinder.

 

Frustrating situation but at least the master cylinder was not damaged and it turned out to be a relatively easy fix in the end.

Good stuff, any news on the exhaust moan?

Slightly on topic, but I've found when fitting rear calipers to these cars that leaving the handbrake cable disconnected until you've bled the system helps a little. Have used the old fashioned pedal method plenty of times and its not damaged anything, only real problems I've ever seen is if the master cylinder runs out of fluid, or if you connect the handbrake cable first it seems to trap a small bubble of air, and your pedal never seems perfect again.

Best way is to bleed the brakes with the engine running. Servo asist and all that, you get a lovely pedal. No damage to master cylinder either.