Brake Pedal gradually going to floor

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6

6Sabre

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Hi all,
I have been having brake issues, I think a result of a period of standing while sorting out an auto gearbox issue (Thanks Hippo). The brake pedal slowly sinks to the floor, if held. I found a leaking rear wheel cylinder so replace both cylinders and the rear shoes. The pedal was still sinking, so I have replaced the master cylinder. After bleeding it was 'sort of ok', and I used it yesterday (15 miles) and they worked but with a bit extra travel (assume rears self adjusting etc).
This morning the brake pedal went straight to the floor, and if pumped will rise, but gradually sink again if held. The only new thing I can hear is a 'relay clicking' by the console/handbrake when I press the brake pedal, which I have not noticed before.
To my knowledge looking at RAVE there are no extra parts I need to look at? My years of experience lead to this still being a master cylinder issue (a new replacement being faulty) but before going back to supplier would like to eliminate any other potential parts. I am not losing any fluid. Thanks Steve
 
Last edited:
If the ABS modulator has an air in the valves or pump, then it's very difficult to get it out, without the use of a diagnostic unit that can activate the pump and open the valves.
If you're lucky, getting the ABS to cycle a few times will shift the air to a location to where it'll bleed out manually, but if the brakes aren't working enough for the ABS to function, a diagnostic unit might be your only option.
 
Hi Nodge,
if it was air in the system, I would expect to be able to pump the pedal up and then have a 'springy' feeling. If I pump up the pedal and then hold it, it sinks.
Yesterday I did use it and it was 'ok' and I did cycle the abs by hard braking in some quiet spots. I have nothing to lose to bleed the brake again anyway and see if things change, so thanks for the suggestion its finding someone locally to do the diagnostic bit.
TBH its the fact I have exactly the same issue as before changing the wheel and master cylinders is the puzzle. I am heading towards a faulty new master, but convincing the supplier may be fun ;-)
 
A bit more. If I repeatedly use the brake pedal with engine off, the pedal goes hard and stays firm. If I then start the engine the pedal will gradually sink to the floor. This points to the servo, but I dont see how a direct acting servo can create this fault. I spoke to the supplier who would be happy to take the MC back and refund if a fault was found, so an easier conversation than expected. However a new servo is £340 for a 2004 FL1..eeek. Had servos apart before, so I think I will remove it and see what I found inside. Dont know what so special about this servo, most LRs are about 150 quid.
 
Just a thought.
Have you had a good look at all flexi hoses while someone stands on the pedal!!??

Maybe without the Servo the rubber holds, but with the increased pressure the pipe expands letting pedal sink to floor?
 
Can't see a failure mode in the Servo that would allow pedal to go down further than with engine off except a leak or hose, as above.
 
andyfreelandy said:
Just a thought.
Have you had a good look at all flexi hoses while someone stands on the pedal!!??

Maybe without the Servo the rubber holds, but with the increased pressure the pipe expands letting pedal sink to floor?
Click to expand...
Such an obvious school boy error on my part, not doing this check! Cheers
 
andyfreelandy said:
Can't see a failure mode in the Servo that would allow pedal to go down further than with engine off except a leak or hose, as above.
Click to expand...
Checked all the flexibles and they are sound. Bled the brakes again today in hope ;-). I then noticed as the pedal sinks (my wife pressing the brake pedal) fluid comes back into the MC. I have ordered another MC and sending the original new MC back for checking as faulty. The supplier will get it checked and refund if they find it faulty, 30 day turnaround. My guess they will just say it got some dirt in it...but we will see. It has to be the MC at fault as I agree with Andy cant see its a servo issue. Thanks to all for ideas, I will update on findings after fitting another MC.

ps. As a matter of interest my local factors contacted their LR supplier for a servo price, and were told they have never heard of a servo failure or ever sold one.
 
Have you taken the wheel hubs off to confirm nothing leaking inside?
Having said that it does sound like the master cylinder is letting fluid past the seal but if they never sold one and suddenly you have two faulty...........
 
Alibro said:
Have you taken the wheel hubs off to confirm nothing leaking inside?
Having said that it does sound like the master cylinder is letting fluid past the seal but if they never sold one and suddenly you have two faulty...........
Click to expand...
Hi Alibro,
Its the servo they have never sold any of.
There are no leaks, they are new rear wheel cylinders and shoes. This all started after a stuck handbrake and when try to free it noticed the sinking pedal. Then when I looked in rear drums to clean/free of all the hand brake bits found a leaking wheel cylinder. I thought that was why the pedal was sinking. After fitting all new stuff no leaks and still a slowly sinking pedal under pressure, so fitted a new MC to have the same issue. I have been working on cars since 1970 (as DIY/restorer) and my experience to date has been a sinking pedal is the MC. I was gobsmacked when the same thing happened after fitting the new MC, which is why I started asking on here as I have been told that happens on certain diesels. Personally I cant see how a servo can cause that. A new one on its way, after chatting to a 'professional' friend who supported the MC idea as the issue. We'll will wait and see ;-) Thanks Steve
 
Oops, I meant to say Servo.
Maybe the new MC you bought has been on a shelf slowly decaying for the last 15 years. ;)
Just for info, I replaced the rear brakes on my 2015 VW Crafter van a while ago and was surprised at how much the pedal sinks when testing. While driving the brakes work perfectly and feel fine but if I press down on them while stationary the pedal slowly sinks to the floor. My previous van, a Ford Transit did the same.
 
Alibro said:
Oops, I meant to say Servo.
Maybe the new MC you bought has been on a shelf slowly decaying for the last 15 years. ;)
Just for info, I replaced the rear brakes on my 2015 VW Crafter van a while ago and was surprised at how much the pedal sinks when testing. While driving the brakes work perfectly and feel fine but if I press down on them while stationary the pedal slowly sinks to the floor. My previous van, a Ford Transit did the same.
Click to expand...
Damn, I might be £60 out of pocket!!
 
Maybe not.
I can't help you by trying my brakes as the car is currently missing a critical part to provide braking assistance.

IMG_20201018_091537424.jpg


Maybe someone else could try theirs to see what happens.
 
An update: I bought another brake master cylinder and fitted it and all is now ok. Pedal pumps up engine off and only sinks a small amount when the engine is started.
Of interest the 1st one supplied was Britpart made in China and the second one I bought (both from Craddocks) is a Lucas MC.
I have returned the 1st one under Craddocks returns scheme and have to wait to see if they confirm its faulty. No question it is faulty, as the new one worked first time.

Thanks for advice to all.
 
Hi all, thank for advice, tips and help.
I have just heard from Craddocks and the supplier has confirmed a fault and I have been issued a refund. Very pleased with the service Craddock's supplied with
their refund process as they kept me informed.
TBH I was expecting them to use a 'get out' and say I got dirt in it. I would have argued as I cleaned the area before strip down and flushed the brake reservoir (and I've been working on cars for 50 years).
Cheers all.
 
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