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Quote:
Originally Posted by Vetcar1
That diagram has to be wrong. The Primary system is the one that operators the front/rear brakes through the priority valve (or is it a rear brake pressure limiting valve). The black line is straight to the front with no valving at all. Certainly not the primary as it can only operate the front brakes!
Yeah, I recall something funny like that and I've probably posted about it before.Quote:
Originally Posted by DoubleChevron
To the OP:
You are aware there are 3 bleed nipples on each of the front callipers? One is kinda hidden.
Also if one of the front hoses is going to the wrong port on a calliper or the all the hoses to the front are mixed up going from the solid lines from the MC you won't be able to bleed it properly.
I had this problem years ago and it was doing my head in............ turned out that on one side at the front the solid lines were installed incorrectly (same effect as hoses being arse about) and it had all the symptoms you describe, once sorted all was good, easy to bleed.
Unlikely to be the proportioning valve IME.
DL
I have on numerous occasions over the years had to bleed my Disco's and Rangie's and found it to be a pain in the backside on all of them, I found out that a lot of mechanics pressure bleed system's nowadays, I thought well I'll get one of these pressure systems but the economics of purchasing one was not economical, that's when I came up with the idea of the syringe and sucking the air/fluid through, I'm not joking when I say it works every time.Quote:
Originally Posted by Vetcar1
I have thought about the problem of the system not bleeding properly when using the break pedal, it seems to me to be an air lock, the air gets trapped inside the master cylinder to one or both of the seals to the Primary or Secondary plungers on either circuit, resulting in half a bleed when you think it should be completed.
This I have notice in the past, can be overcome by topping up the reservoir and letting it sit for 24 or 48 hours (if you want to wait that long) or whatever it takes to let the air escape on its own out through the reservoir above. I have notice that on most occasions no amount of pumping on the brake pedal will rid the M/C of this airlock.
Hence the reason for sucking or blowing.
Regards:-
Patrick M
Attachment 177401Attachment 177402
Bleed nipples in this order.
Also note, If the system is fully serviceable, a soft pedal almost always indicates internal leak in the MC - BUT you need to make sure you have no residual air or contaminants in your hydraulic system to determine this, and that your caliper pistons are not sticky and the calipers themselves are all properly serviceable.
Noone has asked this question though:
Is the pedal still spongy immediately after you've fully bled it, or is is properly ROCK Hard?
If you're testing the pedal's feel with the engine running, you're only evaluating the master vac's ability to assist the pedal, not attending to the actual issue.
a properly bled system will feel very wooden, once all the booster play is eliminated. acting on the hydraulic circuit itself will bring kickback in the pedal, and there is very little compressibility whatsoever - any that you DO feel is the pads acting on the rotors and that is the last 1% of modulation right at the end of travel.
If you have a lot of sponginess or the pedal is still travelling to the floor, then you have an internal leak.
Observe the correct circuits and the hose routing. I also wonder if you have bothered to replace any of the hoses (probably best to replace all of them if you haven't during the last 5 years) because a hose can have internal restrictions and leaks and can internally collapse and rot, all of which has a detrimental and sometimes intermittent effect on downstream components in the hydraulic system.
when all else has failed, disconnecting all the lines from the calipers, and the master cyl, and blowing them clean through with high pressure compressed air, followed by some metho then more compressed air to clean it out, and then a complete bleed from scratch can solve mystery line pressure issues.
Also, make sure the master cylinder was properly bled if it was removed or disconnected for some time. air in the master cyl has a way of refusing to come out once it has entered the bore, and it's a right PITA to bleed on the vehicle. If there is air in the M/C, then pull it off the booster and bench bleed it.
Suggest returning to square #1 and taking your time.
Don't be in a rush.
Brakes are there to keep you alive, mistakes are made when you try to rush a brake job.
From the workshop manual:Quote:
Originally Posted by DoubleChevron
'NOTE: References made to primary and secondary do not imply main service brakes or
emergency brakes but denote hydraulic line identification.'
Kinda funny way of describing the system.
DL
Perhaps “primary” is the circuit from the master cylinder adjacent to the booster.Quote:
Originally Posted by 350RRC
The “secondary” circuit is the one after the internal piston in the master cylinder!
The Primary circuit is affected first by the pressure on the brake pedal, and then the secondary circuit is pressurised from the primary.
Just a thought.
Phil
I use a vacuum bleeder to suck fluid though the lines, there are a few reasonably priced ones on eBay like this one (the one I have but not necessarily this seller) Auto Car Van Brake Bleeder Bleeding Fluid Bleeder Garage Vacuum Tools Kit AA | eBay
It's a really useful tool, just replaced the power steering box with no spills at all, sucked all the old fluid out first, then bled the new one with the same thing. Same goes for all the brake lines. Much better than the manual pumps, and I don't have to pester anyone for help with bleeding.
Thanks again all -
Double Chevron - I tend to agree on your thoughts re my braking diagram being counter-intuitive, but that's what the manual shows. Their reasoning may well be as Phil850 suggests (and as 350RRC quotes from the manual).
350RRC - Yep, have double checked that all the pipe and hose plumbing to the fronts are not mixed up, and also am aware of the three nipples on the front calipers. All good there.
Mercguy - Thanks for that excellent diagram, particularly for the fronts. I'll double check how that aligns with the manual, and if different, will do it as you suggest. To answer your questions - Yes, the pedal is hard immediately after bleeding (with engine NOT running). It only goes spongy when the motor is running. I have replaced all 4 flexible hoses in the front, and the single one for the rear. Re bench bleeding the MC - I didn't do this on my bench, but with the MC mounted on the servo the mobile mechanic cracked each of the four exiting flare nuts while the pedal was operated accordingly. He claimed this effectively bled the MC. Would you agree with that sentiment? It should be noted that after a short test drive all rotors are hot to touch, which would indicate some pressure is getting through to all, just not enough though for safe braking.
Patrick M - I was hoping the fluid level might gravity feed and sort the problem out, but no luck yet. With your syringe system, do you have a fitting on your syringe that screws into the bleed nipples?
The only thing in the entire system that's not new is the pressure proportioning valve. I believe these are a non-serviceable item. Before I renew it out of desperation, i'm just wondering if it would be worthwhile cracking the flare nuts that exit in (just as was done per the ones at the MC) and see if air could be trapped in that? Is that even a possibility?
Thanks again all for your suggestions to date. Rest assured that I will post the eventual solution to this annoying thing.
I purchased a toledo vacuum bleeder a few months ago ... as I have an old car with 4 wheel non-assisted drums here .... It would suck from the reseviour. So I'm thinking I need to pull the master down and see what is going on. I don't do a lot of bleeding, and when I have I've just got someone to pump the pedal for me in the past. All of my cars for the last 30years .... this is how I've bled them.
https://youtu.be/MC_Wkj687Ys
You just open the bleeder .... hold the the pedal down for a bit. I pushed on the brake pedal a few times in this car as it has an ABS module, and I'm not sure if that will bleed properly. I did use the vacuum bleeder as it has a nice connector bit for the bleed nipple. I didn't apply any vacuum The cars here have fully powered brakes. So all I do is hold the pedal down ... and the air is pushed out then the fluid. The hydraulic fluid is green, you can see it flowing down the line and the line bouncing each time I touch the brake pedal. I bled about a cup full of fluid into the bleeder. To do the rear brakes I just run a long line from the bleeder back to the hydraulic reseviour .... and can't just hold the pedal down as long as I like to bleed fluid through.
this is how I'm used to doing brakes .... I'll try the vacuum bleeder on the range rover this weekend and see if I can get it to work (failing that, I'll get one of my kids to pump the pedal for me ).
I have no probs at all these days bleeding the brakes with either the AP MC or the later Lucas Girling MC as per the manual.
There is a trick to getting the last tiny bit of air out of the rear callipers, but it's a very minor issue to do with pad wear.
DL
