S2 Long pedal travel
Discussion
Hi,
I had long felt that my brakes were not quite as sharp as expected so recently fitted new stainless braided hoses, front pads and had the front callipers refurbished.
I have since driven approx 500 miles and bled the brakes several times (most recent getting the pros to do it), however the pedal still does n't feel right. Key facts are these:
1) The pedal can be pressed about 25mm (engine not running) before resistance is felt.
2) If I start the engine with the pedal pressed it drops a little.
3) When driving if I go to brake the pedal seems to have a small amount of resistance fairly quickly but this small amount of resistance seems to continue until the pedal is quite a way down before deceleration is significant.
4) If I pump the pedal with the engine running I get a hard peddle and it does n't go down further under firm pressure (I compared my definition of firm by doing the same in my 2003 Passat).
5) When the engine is off if I push the pedal slowly a couple of times the point of maximum resistance increases (i.e. the pedal gets higher).
6) I have noticed that the rubber hoses going between the remote reservoir and the master cylinder look like they are getting condensation on them after the car has been stood for a couple of days. This feels oily. No other hoses in the engine bay get this condensation.
7) If I jam the brakes on hard then I can lock the wheels and the car pulls up in a straight line.
8) I can't see any obvious fluid leaks from any of the joins in the hydraulic system.
I have read that air can get into the system without any fluid getting out. Based on this I'm thinking that I either have:
1) A slow air leak
2) The hoses between the reservoir and master cylinder have gone porous and are letting water/air into the fluid.
3) Master cylinder seals shot
I favour 2 as a theory but have never heard of this before...what do others think? am I missing something?
Thanks,
Ralph
I had long felt that my brakes were not quite as sharp as expected so recently fitted new stainless braided hoses, front pads and had the front callipers refurbished.
I have since driven approx 500 miles and bled the brakes several times (most recent getting the pros to do it), however the pedal still does n't feel right. Key facts are these:
1) The pedal can be pressed about 25mm (engine not running) before resistance is felt.
2) If I start the engine with the pedal pressed it drops a little.
3) When driving if I go to brake the pedal seems to have a small amount of resistance fairly quickly but this small amount of resistance seems to continue until the pedal is quite a way down before deceleration is significant.
4) If I pump the pedal with the engine running I get a hard peddle and it does n't go down further under firm pressure (I compared my definition of firm by doing the same in my 2003 Passat).
5) When the engine is off if I push the pedal slowly a couple of times the point of maximum resistance increases (i.e. the pedal gets higher).
6) I have noticed that the rubber hoses going between the remote reservoir and the master cylinder look like they are getting condensation on them after the car has been stood for a couple of days. This feels oily. No other hoses in the engine bay get this condensation.
7) If I jam the brakes on hard then I can lock the wheels and the car pulls up in a straight line.
8) I can't see any obvious fluid leaks from any of the joins in the hydraulic system.
I have read that air can get into the system without any fluid getting out. Based on this I'm thinking that I either have:
1) A slow air leak
2) The hoses between the reservoir and master cylinder have gone porous and are letting water/air into the fluid.
3) Master cylinder seals shot
I favour 2 as a theory but have never heard of this before...what do others think? am I missing something?
Thanks,
Ralph
Spathodus77 said:
I favour 2 as a theory
I don't !Any strange migration or air or moisture into the brake fluid would take time, you should still get a "good pedal" immediately after bleeding.
Air would, as air does, go uphill towards the reservoir and not down into the master cylinder?
Moisture would , in theory, have to get all the way down top the callipers/wheel cylinders where it would then get hot and boil before having any effect. Just like brake fluid, water cannot be compressed (only when it boils and turns into a gas), ask anyone who has driven a car with a low air intake through a deep ford......
Were all flex hoses changed, front and rear? definitely no leaks (even minutely slight, obviously not pissing out) at any joins?
Master cylinder could be passed its best, this may show as brake fluid dribbling down the servo where the two join.
failing that my money is on air still in system, only needs the tiniest amount!
Edited by phillpot on Monday 24th August 04:56
I agree with Mike that 2 is very unlikely, never heard of it.
Can I just ask a question? When you have the pedal depressed and THEN start the engine there should be a very pronounced change if not I wonder if the servo is working properly?
Have you (carefully!) separated the master cylinder from the servo? It can be done with care with the pipes on. If there is any sign of fluid or muck in there then the master cylinder is suspect. Unfortunately fluid leaking from the cylinder can get into the servo and damage it, or run down the servo and cause rust in the joint underneath causing the servo to leak.
Of course if fluid is leaking from the master cylinder then air is likely to be getting in as well when the piston moves.
When you separate the master cylinder be careful of the rod from the servo which operates the master cylinder, it may have a facility for adjustment which has to be kept just right.
Lets hear what you find.
Can I just ask a question? When you have the pedal depressed and THEN start the engine there should be a very pronounced change if not I wonder if the servo is working properly?
Have you (carefully!) separated the master cylinder from the servo? It can be done with care with the pipes on. If there is any sign of fluid or muck in there then the master cylinder is suspect. Unfortunately fluid leaking from the cylinder can get into the servo and damage it, or run down the servo and cause rust in the joint underneath causing the servo to leak.
Of course if fluid is leaking from the master cylinder then air is likely to be getting in as well when the piston moves.
When you separate the master cylinder be careful of the rod from the servo which operates the master cylinder, it may have a facility for adjustment which has to be kept just right.
Lets hear what you find.
Did you do anything with the rear brakes? If you haven't set the seft adjusting mechanism up right on either wheel, you could get excessive play at the pedal til the cows come home. Otherwise, I agree that there's air in the system somewhere. The favourite place for it to hide on my S was in the rear brake limiter valve - situated on the bulkhead behind the servo - a right bleeder to bleed.
Just for info... Re. Your first no. 2....about the pedal moving down when you already have your foot pressing on it when you turn the engine on...this is normal - and is one way vehicle examiners test for an effective servo unit - the added assistance of the servo will allow the pedal to move down even more - just doing its job.
Just for info... Re. Your first no. 2....about the pedal moving down when you already have your foot pressing on it when you turn the engine on...this is normal - and is one way vehicle examiners test for an effective servo unit - the added assistance of the servo will allow the pedal to move down even more - just doing its job.
NaCl said:
Did you do anything with the rear brakes? If you haven't set the set adjusting mechanism up right on either wheel, you could get excessive play at the pedal til the cows come home.
Thought of this one after I'd gone to bed last night, self adjusters may not be "self adjusting"? Does the pedal travel improve with handbrake on?Thanks for all the advice.
I've been able to investigate a bit further today and I can confirm that there is no improvement in the pedal whether the handbrake is off or on. I did the rear brakes (wheel cylinders + stainless hoses) about five years ago. Since then I've had no braking issues until now...
I've checked all the hose connections front and rear. There was no visual indication of fluid leaking out anywhere. The two pipe connections out of the master cylinder that are furthest from the servo felt a bit looser than I'd like so I nipped them up. I then wiped round the connections where the hoses go into the front callipers and thought there might have been a trace of liquid on the kitchen roll but then again maybe there was n't...
Feeling despondent I bleed the front brakes,hoping that the trace of liquid may lead to some air coming out, but the fluid was clear. As a last resort I then bled the rear (yes, I know wrong sequence), offside = no bubbles - nearside (after a while) loads of them. Pedal now feels much better but I am left with the worry that there may be a slow leak somewhere.
I have yet to split the master cylinder from the servo - maybe a job for tomorrow. In the meantime if anyone has any further thoughts I'd be keen to hear them.
Ralph
I've been able to investigate a bit further today and I can confirm that there is no improvement in the pedal whether the handbrake is off or on. I did the rear brakes (wheel cylinders + stainless hoses) about five years ago. Since then I've had no braking issues until now...
I've checked all the hose connections front and rear. There was no visual indication of fluid leaking out anywhere. The two pipe connections out of the master cylinder that are furthest from the servo felt a bit looser than I'd like so I nipped them up. I then wiped round the connections where the hoses go into the front callipers and thought there might have been a trace of liquid on the kitchen roll but then again maybe there was n't...
Feeling despondent I bleed the front brakes,hoping that the trace of liquid may lead to some air coming out, but the fluid was clear. As a last resort I then bled the rear (yes, I know wrong sequence), offside = no bubbles - nearside (after a while) loads of them. Pedal now feels much better but I am left with the worry that there may be a slow leak somewhere.
I have yet to split the master cylinder from the servo - maybe a job for tomorrow. In the meantime if anyone has any further thoughts I'd be keen to hear them.
Ralph
Try bleeding rears again with handbrake on, then with it off, then on again. If the air reappears then you really have to check that rear wheel cylinder. Depending on how much use the car has had, a cylinder seal could easily have stuck and been damaged in that time. I was surprised that one of mine started to fail after 6 years, it wasn't that obvious but an MOT brake test suggested an out of balance and that was the cause. When it was stripped it was clear a little rust had started in the cylinder and damaged the seal.
Did you buy the stainless pipes made up, or make them up yourself?
Did you buy the stainless pipes made up, or make them up yourself?
Philpot - where did your "I told you so" post go? 
The brake hoses were made up for me by well known companies. The car has done about 7500miles since I did the rear wheel cylinders and is always garaged, although I do drive it in the wet on occasion.
I'll have another play tonight and hopefully get the car over to Neil Garners tomorrow so they can feel the pedal and hopefully give me a pro opinion on whether the master cylinder is good or not.
The brake hoses were made up for me by well known companies. The car has done about 7500miles since I did the rear wheel cylinders and is always garaged, although I do drive it in the wet on occasion.
I'll have another play tonight and hopefully get the car over to Neil Garners tomorrow so they can feel the pedal and hopefully give me a pro opinion on whether the master cylinder is good or not.
You don't attain idol status for correct problem diagnosis though! - that goes to greymrj 
I just pulled back the dust boots on the rear wheel cylinders and brake fluid started dripping out. I checked the invoice and I only fitted the last set in 2009.
Thanks to all for the advice. I'm hopeful that I can now sort this out.
I just pulled back the dust boots on the rear wheel cylinders and brake fluid started dripping out. I checked the invoice and I only fitted the last set in 2009.
Thanks to all for the advice. I'm hopeful that I can now sort this out.
Thanks Ralph, very glad you have found something definite. I would make one further suggestion: while you have the brake dismantled check the automatic adjuster, they seize and also the teeth on the cam wear. A little bit of work here can make a surprising difference. See
http://www.pistonheads.com/gassing/topic.asp?t=149...
http://www.pistonheads.com/gassing/topic.asp?t=149...
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