BRAKE PEDAL - EXCESSIVE TRAVEL

[Tedb 0]

There is quite an amount of travel in my brake pedal (2.0l 16v with ABS) before the brakes begin to bite, I'd say 3 inches or so of excess travel. The brakes are quite good when they engage but I recall the pedal being better. The Pedal doesn't feel at all spongy, it's just theres quite a gap in the travel before the brakes engage. I recently had to remove the ABS Pump for repair (in the end it wasn't necessary as the fault was a Relay Switch) but the brakes have been unsatisfactory since. No other work was done to the Brakes.

 

I have bled them numerous times both with the Ignition on and ignition off but it doesn't make any difference in the result, it hasn't tightened up the pedal. I am getting a prefectly good flow of cean fluid and there is no evidence of any air in the tube when they are being drained. I am using the One Man Gunson Ezi-bleed Kit. I have also bled all the inlets and outlets of the ABS Pump and the Master Cylinder and there is no evidence of any air there either. I have bled the brakes both starting with the caliper nearest the Master and starting with the caliper furthest from the master, it doesn't make any difference to the result.

 

Any ideas how I might improve this would be appreciated.

 

It's currently preventing me from taking the MOT as I sense it won't pass.

 

Cheers

[Neale_E 0]

Hi there Tedb.

 

I don't know if I have a definitive answer for you but it sounds very similar to my recent experiences. I will say now I haven't fully proved my conclusions but they do seem to fit.

 

I have a 1995 VR6 which I have been doing a complete re-build on the rear. The car had been standing in my garage for about a year before I was able to get to it.

 

After getting it all back together just couldn't get the pedal. Tried all methods and although got some improvement when we pressure bled with the engine running (doing rapid depressions on the pedal to get the fluid through the ABS) we just couldn't get enough of an improvement.

 

I did loads of searching and reading here but nothing quite fitted.

 

I went round all connections etc. checked and re-checked everything.

 

Eventually bit the bullet and took it for a test drive (the night before the MOT) on the unadopted road in front of my garage. The brakes seemed to be working (car braking evenly and not pulling) but just couldn't get the pedal any better. If I pumped the pedal with the engine running it did come up a bit. But still poor even by C standards.

 

Decided to take it for the MOT anyway as even if it failed the results might give me a better idea where to look.

 

Turned out the brake pressures were A1 all round and even from wheel to wheel (so it wasn't air) but the pedal was still poor.

 

The clincher was that on the dials the needles didn't move till the pedal was half way down. But once they move the brakes came on great.

 

Our conclusion (which I am goint to hopefully prove this weekend) is that the return spring in the Master cylinder was weak or had broken. So it wasn't returning the piston properly. It took an amount of travel to engage the piston and start to move it.

 

I have got a replacement master cylinder and if all goes OK I will have a decent pedal sometime on Sat.

 

I will let you know my results (good or bad).

 

Neale_E

[plateletboy 0]

very interested in the outcome of this one....

sounds exactly like my VR6 pedal feel. bites well, but only about half way done, and it was all fine at the MOT...

 

pb

[Supercharged 2]

Hmmm - replacement MC's are not a bad thing considing most of our cars have had new flexi's, new solid lines and new calipers from age / wear...

 

New masters are alloy now so hopefully won't corrode like the old ones, worth cecking the servo condition while your there altho not a cheap part to replace - they can leak where they are welded together when they corrode so worth checking if you see any particular amount of rust...

[Tedb 0]

Thanks for the replies guys, Neale, have you fitted that Master Cylinder yet and did it make a difference? I'm going to bleed the whole system again this weekend, I never tried bleeding with the Engine Running, what's the theory behind this? Surely it's bad for the ABS Pump?

[Neale_E 0]

Hi Tedb,

 

No, sorry, not had time as yet. Busy week with work and dog just come back from vets.

 

Planning to change the M.S. on Sat. morning and then see what happens. I will try to post straight afterwards - especially if it fixes the brakes.

 

I had been having exactly the same symptoms as yourself. Firm, consistent pedal but way too much travel. I know that the rear calipers were in good working order and that they were correctly adjusted. All the discs and pads were in a good condition and the hoses had been replaced with Goodrich braided. So there wasn't much it could be.

 

I was convinced it had to be air - somewhere.

 

I went to a local VW specialist (not a main dealer - pretty useless for anything more than a few years old) and asked a mechanic there who I knew. He went through the usual list of checks and said the C brakes with ABS could be a real pain to bleed sometimes (you kind of get this feeling by the number of bleed points anyway). Especially if you got air in the ABS as it can just sit there, even with pressure bleading.

 

His advice was to connect the pressure bleeder to the master cylinder and as I had one, a brake bleed kit with the non-return valve to each wheel in turn (start with the shortest circuit - I think this will be the N/S Front). Then, at each wheel, do 1 or 2 normal depressions of the pedal to get the fluid moving followed by 5 rapid depressions (I actually did 10 on the front and 20 on the rears). This is a two person exercise as you need to ensure that you tube dosen't come off the bleed nipples.

 

Be carefull and I would strongly recomend wearing safety glasses in case the hose pops off and you get sprayed with fluid.

 

The engine needs to be running so that the ABS pump is running and also to give you necessary assistance when you do the rapid depressions (as if you were doing and emergency stop). The sheer flow of the fluid plus the pump running should shift the air from wherever it is lodged and hopefully out.

 

When we did it I initially got clean fluid but then could see a stream of dirty fluid (and a little air) so it definately shifted some old fluid from somewhere.

 

I believe that if you have a VAG-COM you can actuate the ABS through that, but I don't, so this was my best hope.

 

One word of warning - there is a risk that you could knacker your M.C. seals. On a worn M.C. there will a slight step near the end of the travel - and poss. a sharp edge. If your seal passes over this it could strip it and there goes you M.C.. I only use a pressure bleader now after learning this the hard (and expensive) way some years ago.

 

I would like to write a WIKI on C brake bleading as there is a lot of info on this site but it is in bits all over the place. A concise point of reference for all would be great.

 

I will post my results asap.

 

If it is the M.C. then bleading again won't do any good,. I have put at least 4 litres through up to now - A1 brake but still way too much travel. If I do the M.C. right I won't need to blead it again (I hope).

 

Neale_E

[Neale_E 0]

Oh yes... just remembered something.

 

Make sure the balance valve on the rear beam us fully open (hard up against the valve body) to get good flow through it (I know this is covered elsewhere but might as well mention it here).

 

Also one sign that your M.C. seals are knackered is that the fluid level in the reservoir will rise very slightly as you depress the pedal. Though this can be difficult to see and is by no means conclusive.

[Tedb 0]

Thanks Guys for the replies and in particular Neale's comprehensive one, I'm not sure if there is a balance valve on the 16v, is this the brake equaliser thing?

and what way sould it be again? I'm afraid I dont have anyone that can help me with the bleeding excercise so I'll have to stick to my one man ez bleed kit which connects to the Master and your spare tyre to give the pressure, would it be safe to use the one man kit with the engine running or would the pressure from the pump and the pressure from the ez bleed connected up to the Master and spare tyre as specified be too much pressure?

 

Cheers

[Neale_E 0]

Hi Tedb,

 

In answer you your questions, yes it could be the brake equaliser thingy (very technical terms). If you have one it will be near the rear beam on the N/S (have a look at the WIKI on changing rear bushes - there are some pics of it there for sure). Can't miss it....honest.

 

As far as connecting yor ez bleed with the ABS pump running I haven't had any problem here myself. I don't think there is any real additional pressure unless the ABS actually pulses. Which won't happen with the car standing.

 

As far as results on mine. Just got back from the garage and there is some improvement in the travel. Sorry can't be more conclusive than this.

 

I have fitted a 'tested' second hand unit. I was going to fit a new aftermarket M.C. but the one I was shown didn't match mine and their card machine wasn't working. I know that a new VW one is around £190. Will make enquiries about a new aftermanrket on Mon. If not the I guess it's VW .... ouch.

 

So I think at least part of my problem is certainly the M.C. the rest may well be just the car. I have never known C brakes to be really firm on the pedal.

 

Hope you have more success.

 

Neale_E

[Neale_E 0]

I've been thinking.... oops not a good idea.

 

There won't and can't be any pressure from the ABS pump otherwise the brakes would be ON.

 

The ABS will only 'pulse' the pressure in the system if it sees a wheel locking under breaking.

 

So the idea that the ABS pump pressurising the system is a mis-conception.

 

If anything it reduces the pressure to allow the wheel to turn.