v8250
Well-Known Member
Marc, have just seen your post. Brakes can be a real challenge sometimes, so it's worth starting from scratch knowing what's good in the system then methodically fault find. Really, brake systems are very simple.
To confirm the following items are new:
Brake Servo
Brake Master Cylinder
Bias Valve
Front Calipers rebuilt
any thing else...?
1. is the brake bias valve the right way round?
2. as previously mentioned, isolate the output of the master cylinder and check pressured fluid
3. check first brake line output, as #2
4. then slowly bleed the system as per the manual - in the following order, rear left or right brake depending which is furthest from the master cylinder [left or right hand drive], then next rear brake, followed by the front brakes
5. you will get a hard brake pedal at each corner when completely bled and the individual line has no air present
6. completing in the above sequence will isolate the faulty section/brake corner and highlight where the problem exists
6. if brakes are still not bleeding properly, and/or, the brake pedal 'feel' is not right your problem lies with either the master cylinder, the servo or one of the calipers [slave cylinders if rear drums]
Another area to check are the bleed nipples - are they brand new and are they and the caliper spotlessly clean?
+just re-read part of your posts, have you raised the corner of the LR so the brake being bled is higher than the other brake corners? - this aids any potential air trapped mid way to rise and escape.
++sometimes it just takes an age for the air to fully escape/bleed and for the system to be completely full of brake fluid - this is why one should always start the bleed at the brake furthest from the master cylinder.
Good luck, be patient and they will come right
To confirm the following items are new:
Brake Servo
Brake Master Cylinder
Bias Valve
Front Calipers rebuilt
any thing else...?
1. is the brake bias valve the right way round?
2. as previously mentioned, isolate the output of the master cylinder and check pressured fluid
3. check first brake line output, as #2
4. then slowly bleed the system as per the manual - in the following order, rear left or right brake depending which is furthest from the master cylinder [left or right hand drive], then next rear brake, followed by the front brakes
5. you will get a hard brake pedal at each corner when completely bled and the individual line has no air present
6. completing in the above sequence will isolate the faulty section/brake corner and highlight where the problem exists
6. if brakes are still not bleeding properly, and/or, the brake pedal 'feel' is not right your problem lies with either the master cylinder, the servo or one of the calipers [slave cylinders if rear drums]
Another area to check are the bleed nipples - are they brand new and are they and the caliper spotlessly clean?
+just re-read part of your posts, have you raised the corner of the LR so the brake being bled is higher than the other brake corners? - this aids any potential air trapped mid way to rise and escape.
++sometimes it just takes an age for the air to fully escape/bleed and for the system to be completely full of brake fluid - this is why one should always start the bleed at the brake furthest from the master cylinder.
Good luck, be patient and they will come right
v8250
Well-Known Member
are you sure the brake servo diaphragm is not split and that you have proper vacuum in the servo? brake fluid will quickly disappear into the vacuum side of the servo if the diaphragm is split -this shows up as little to no brake pedal pressure
sharkey964
Active Member
Thanks for taking the time to post this.
The only thing I haven't replaced on the front brakes is the servo.
The rear brakes I haven't touched!
I have NOT been bleeding starting at the furthest caliper away,as I only changed things on the front.Though,as I've changed the Bias valve,I suppose this will have let air into the rear system as well as the front?
Why do the bleed nipples need to be good?The fronts are new,as are the calipers.but the rears are not new.
I'll do everything again tomorrow,following your guide.
Wish me luck.
Thanks again.
Marc
sharkey964
Active Member
v8250
Well-Known Member
Marc, are the rear brakes drums or discs?
1. it's near impossible to not trap air in the system when only work on the fronts or rears. There are some tricks to not do this, but in your situation you should be changing all the brake fluid :. fill brake MC and start from furthest brake from MC - this clears any trapped air to the majority of that brake line [not all as there'll still be some to the front line on a dual system], then the next furthest...or, the front line of the same dual line [you may find it easier to manage doing it this way as you will know that you have 1x good line with no air]
2. then complete the next furthest from brake MC [usually the other rear] [often on cars this is the opposite front corner to the brake servo/MC], followed by the last front corner, ideally nearest in pipe length to the MC.
3. during the above you must not allow the brake fluid to drop/allow air in to the reservoir - if you do this you will trap air in the system and you'll have to start again!
4.so, by now you'll have good qty of brake fluid with, theoretically, no air...but there's always some trapped in the lines...so re-bleed all four corners again, methodically, and 'feel' as the brake pedal firms up properly.
if this doesn't happen you've a fault in the system which needs tracing out. start with the brake flexibles as they're easy. Actually, if it was me and the flexibles were of a certain age I'd replace them as defacto; your choice. If still poor brake feel and you're 100% there are no leaks [leaks let out fluid under pressure from the pedal/MC...but, suck in air on the return stroke!] the fault lies with either the brake MC, servo, vacuum pump or the brake balance valve.
1. you've installed a brand new MC...did you fluid through the MC before installing? Or, did you install dry?
2. your old vacuum pump could be worn :. not producing enough vacuum at servo & this would give poor brake feel
3. have you fired up the LR to produce vacuum? get a proper feel of the brakes?
4. check balance valve is installed correctly
v8250
Well-Known Member
Test the servo with a hand pump & low pressure gauge [don't over pressurise, 0.5-1.0 bar is plenty to test], if the servo diaphragm is split the servo won't hold continuous pressure [:. you'll get poor brake pedal feel as every time you press the brake pedal you'll lose the vacuum through the diaphragm] Whilst under test pressure you will get a +Ve feel at the brake pedal/see the pressure rise on the gauge as it's now a sealed system. Now, all this is bit of a faff so if your servo is old and crusty, and most are, just buy a new unit and be done with it
Now, where do I send my invoice too...?
v8250
Well-Known Member
Because old bleed nipples, especially on old Landy's, will be crusty and one never knows if a clumsy previous owner has x-threaded/split the nipple which will allow air into the system
sharkey964
Active Member
v8250.....
Thank you so much for your in depth description,& advice.
So,this morning I bled everything through AGAIN,but this time as you recomended,starting with the furthest wheel from the MC.Also jacking up each wheel in turn,to giv a high spot for any air to rise to!!!
Tried it.....NO diferent......
So,I thoght,go back to the begining.
Starting at the new master cylinder.
When I took it off I noticed a mark or a bit of damage on the piston,checked the old one,no marks or damage on that one.
Looked into the hole in the servo,& the rod that locates in the piston of the MC had fallen out of position,so therefore not engaging inside the piston.
Assembled it again making sure the rod was located in the MC piston,bled up as above.......YAAAAY!....I have brakes.
I still need to road test tomorow,but fingers crossed Ihave got to the bottom of the problem.
I would like to say a massive thank you to everyone who has taken their time to give advice on this.
This forum is brilliant & invaluable to all who want to be as involved in the maintainence of their Land Rovers.
Marc
Thank you so much for your in depth description,& advice.
So,this morning I bled everything through AGAIN,but this time as you recomended,starting with the furthest wheel from the MC.Also jacking up each wheel in turn,to giv a high spot for any air to rise to!!!
Tried it.....NO diferent......
So,I thoght,go back to the begining.
Starting at the new master cylinder.
When I took it off I noticed a mark or a bit of damage on the piston,checked the old one,no marks or damage on that one.
Looked into the hole in the servo,& the rod that locates in the piston of the MC had fallen out of position,so therefore not engaging inside the piston.
Assembled it again making sure the rod was located in the MC piston,bled up as above.......YAAAAY!....I have brakes.
I still need to road test tomorow,but fingers crossed Ihave got to the bottom of the problem.
I would like to say a massive thank you to everyone who has taken their time to give advice on this.
This forum is brilliant & invaluable to all who want to be as involved in the maintainence of their Land Rovers.
Marc
sharkey964
Active Member
I changed one of the rear bleed nipples,just because the spanner was starting to round the nut head.
Marc.
