J

Jock666

New Member
Hi all. 1st off I'm a very experienced mechanic but this 1 this evening is a cracker - so before I go the long way fault finding lets hear what you have to say....
2000 Td4 manual.
Changed front pads/discs today - no problem previous owners had looked after it fairly well. Symptoms before change were worn /warped discs resulting in a 1/2 way pedal on 1st pump and full on 2nd - no problem and it's just been for MOT last week & passed.
Changed out for the new disc/pads, lubed everything, pushed the pistons back to zero (single piston calipers), checked fluid - bit high now so syringed out a little from top of resevoir, fitted wheels, pumped up without engine running - 3 pumps to get pistons out & into in place and went away for few hours until rain went off. No problem.
Gone out to move it - hard pedal when engine off (reasonably) fire it up, pedal is up, hold the pedal and it goes to floor.......WHY ?
Nothing has been changed or mucked around with so what has happened - ideas folks pls
 
I would think thet the clue is you had to pump the brakes from your description before the work. could be air in the system, or as I had, a problem with very old fluid, other than that I'd be looking at the master cylinder.
 
It's a possibillity but when discs are worn enough the system can require a bit extra fluid to move pistons full travel - hence the slight uplift of pedal with 2nd pump and as they were fully functioning - did 1800 miles with it over last 5 days - I'm inclined to look elsewhere.
 
Jock666 said:
It's a possibillity but when discs are worn enough the system can require a bit extra fluid to move pistons full travel - hence the slight uplift of pedal with 2nd pump and as they were fully functioning - did 1800 miles with it over last 5 days - I'm inclined to look elsewhere.
Click to expand...
No way, you should never have to pump the brakes, they may have functioned but they were not right. The pads/piston do not withdraw far from the surface of the disc when the pedal is released so the fluid stays in place.
Either there is air in the system, the fluid is old or the master cylinder is on it's way out.
 
You pushed the fluid back into the system :doh:
You could easily have damaged the ABS modulator or the master cylinder.
The excess fluid should always be removed from the system via the bleed nipple with the flexy hose clamped.
 
Nodge68 said:
You pushed the fluid back into the system :doh:
You could easily have damaged the ABS modulator or the master cylinder.
The excess fluid should always be removed from the system via the bleed nipple with the flexy hose clamped.
Click to expand...

very unlikely, but its is likely he has air in system
 
sounds to me like either there is air in the system or even the adjuster strut in the rear brake drum has colapsed. it would result in a hard pedal first push then nothing intil the adjuster has either been fixed or readjusted itself. If it is the adjuster then it can take a good half hour of pumping to readjust the the adjuster.
 
Cheers folks. My thinking is going to abs modulator after removing drums (all new shoes, clips, adjusters etc). Re pushing caliper pistons back - never had a problem with this in 30 years - it's a actually just reverse bleeding a system - very common on motorbikes etc. However there is always a 1st time! Just went to bleed calipers and....both nipple hidden under rubber caps - are 50% rusted away! no point messing around with them will just replace - so off to feebay now for a couple of cheap new ones. The saga continues. Will put new post on similar but unrelated issue now.
 
Jock666 said:
Cheers folks. My thinking is going to abs modulator after removing drums (all new shoes, clips, adjusters etc). Re pushing caliper pistons back - never had a problem with this in 30 years - it's a actually just reverse bleeding a system - very common on motorbikes etc. However there is always a 1st time! Just went to bleed calipers and....both nipple hidden under rubber caps - are 50% rusted away! no point messing around with them will just replace - so off to feebay now for a couple of cheap new ones. The saga continues. Will put new post on similar but unrelated issue now.
Click to expand...
Motorbike brakes, unless they have ABS are nothing like cars with ABS.
Pushing the pistons back does not reverse bleed the brakes, it just pushes the air up the pipe a bit.
If the fluid is over 5 years old it should be replaced.
 
Jock666 said:
Cheers folks. My thinking is going to abs modulator after removing drums (all new shoes, clips, adjusters etc). Re pushing caliper pistons back - never had a problem with this in 30 years - it's a actually just reverse bleeding a system - very common on motorbikes etc. However there is always a 1st time! Just went to bleed calipers and....both nipple hidden under rubber caps - are 50% rusted away! no point messing around with them will just replace - so off to feebay now for a couple of cheap new ones. The saga continues. Will put new post on similar but unrelated issue now.
Click to expand...

ive never seen it be a problem though its possible you sucked some air in at piston
 
Jock666 said:
It's a possibillity but when discs are worn enough the system can require a bit extra fluid to move pistons full travel - hence the slight uplift of pedal with 2nd pump and as they were fully functioning - did 1800 miles with it over last 5 days - I'm inclined to look elsewhere.
Click to expand...

This can happen if the discs are warped, and hence the pistons get pushed back in the calipers a little further - but no way to the extent that you need to pump the brakes to stop the car.

You may have had issues with worn friction linings and discs but to have to pump the brakes you probably have a major hydraulic problem, first step should be changing the fluid and if it's really cacky, doing it again a few days later.

I have had a problem in the past (on a Jag not a LR) where the fluid got really back and I had to take the ABS valve block out and blow compressed air through it etc.
 
Rave tells you to slacken the bleed nipple before pressing the piston back into the caliper when fitting new pads - so obviously not intended to force fluid "backwards" through system
 
Jonty1 said:
Rave tells you to slacken the bleed nipple before pressing the piston back into the caliper when fitting new pads - so obviously not intended to force fluid "backwards" through system
Click to expand...

Absolutely. In the dealership I worked at it was a disciplinary offence to push the old fluid back into the system. This is due to the fact that it can damage the ABS modulator.
 
Well 2 x new front callipers arrived today, fitted and brakes bled all around - 3/4 litre through them (vac bleeder) to really clean pipes out. Only dram is rear bleed nipples are virtually touching the brake cylinder - real p1g to get into and move open them. No change - pedal straight to floor - can feel the boost though, pump up hold and straight to floor.
Loosened off master cyl to have a look - dry as a bone no leaks anywhere. All copper pipes were renewed late last year - all good, no leaks. ABS pump fine, no leaks.
In summary - all parts look fine, no leaks, no kinks, no clamps left on (never used any in 1st operation anyway), new pipes, new rear cylinders, new front callipers, new fluid - my guess: modulator has failed....anyone?
Now got the 3 amigos to deal with! - just ordered a new brake pedal switch (the cheap one with 2 wires) in case - was this also a problem on the Mk 1's?
 
Does the FL have a special bleed proceedure like the P38? If it does, there may be air in the modulator if it hasn't been done properly.
 
Pressure bleed them and put more than 3/4 litre through the system....:(

You could be sucking air in..
 
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