Bleeding brakes ( or not as the case may be )

Hope someone can shed light on this.
Started with a slight pull to the left when braking.Got progressivley worse over time and also have had a few instances of no brakes at all. No obvious problems on inspection ,pads ok etc. so decided to bleed. This system is not like anything i have done before. Found a good description on 'search' and by coincidence was detailed in last months LR monthly. Followed to the letter or would have done if only i could get fluid to flow.
A little from rears
None from N/S outer lower
V little from N/S inner lower
loads from N/S upper
A little from O/S outer and inner lower
loads from O/S upper
Pump,accumulator,and both boosters bleed well

I presume pedal travel is not like conventional systems mine is hard all the time and when 'pumped' appears to have little or no effect.
All advice gratefully accepted

Hi mate.

I assume you have checked the obvious, ie the condition of the pipes?

The pedal should not be hard all the time. Does your pedal return okay?
It may be a leak in the servo area or are you ABS?

Have you flushed the system with new fluid and the same results? I wonder if your master cylinder is needing a refurb orthe pressure regulator is borked, although that going is rare.


Any more info?

I completely rebuilt the brake system last year.

Hi
Sorry should have been a little more precise.
1995 softdash ( Plymouth Blue by the way ) ABS with TC.
This is a first for me on this car. Am more used to conventional systems where the pedal hits the floor when bleeding.
What really concerns me is that I can't get any fluid to flow from some of the nipples.
Thanks for reply

Mine dissnae have ABS (thankfully) so I don't know too much about the abs on the Rangie. It could well be the abs pump or ABS modulator block that has a seized valve.

Are you sure the pump is running? I think I can remember how to test it with a multimeter.

Oh I forgot about the pressure switch.

I'm beginning to wish mine didn't have either
Yes pump is running and cycling .Ithink it must be something in the modulator but have no experience of these and be damned if I can find info/diagrams .

Have you downloaded RAVE? It has a fair bit of stuff in it

I'm not an abs expert, but they are on here and perhaps they could help.

Tried before but gave up ,probably due to poor computing skills.Will give it another go and also hope an'expert' comes along soon .thanks

chrisrr said:

Hope someone can shed light on this.
Started with a slight pull to the left when braking.Got progressivley worse over time and also have had a few instances of no brakes at all. No obvious problems on inspection ,pads ok etc. so decided to bleed. This system is not like anything i have done before. Found a good description on 'search' and by coincidence was detailed in last months LR monthly. Followed to the letter or would have done if only i could get fluid to flow.
A little from rears
None from N/S outer lower
V little from N/S inner lower
loads from N/S upper
A little from O/S outer and inner lower
loads from O/S upper
Pump,accumulator,and both boosters bleed well

I presume pedal travel is not like conventional systems mine is hard all the time and when 'pumped' appears to have little or no effect.
All advice gratefully accepted

Click to expand...

Bleeding the ABS system is a right game. I once used 15 litres of brake fluid bleeding mine.

Anyway, something's not right. Have you checked for a blink code from the ABS ecu to see if there are any faults stored? If there was a fault, the ABS and/or ETC warning lights should be on.

Assuming all is good, you need to get a workshop manual and follow the instructions to the letter. Depressurise the system first, top up fluid reservoir to MAX.

Press the pedal 5 times slowly using the full pedal stroke. Release pedal wait 5 - 10 sec.

Bleed hydrostatic circuit first, then bleed hydraulic pump. Next bleed accumulator then the two hydraulic booster screws.

Next bleed the power circuit, these are the upper bleed screw on the front caliper and obviously the only bleed screws on the rears. You only need to run the pump for a few seconds for each bleed screw (the same is true for the hydraulic booster)

Next is bleed the master cylinder - run the pump, if it doesn't stop within 45 secs, you either have a leak or there is still air in the system somewhere.

Last operation, bleed the hydrostatic circuit calipers. Make sure you only use the bottom two thirds of the pedal travel - Open ONE front lower caliper bleed screw, activate pedal several times (lower 2/3 only) until fluid is clear of bubbbles. Stop if fluid waning light comes on and allow pressure to build.

That's the "short" version, hope that helps and best of luck.

If none of that works then it may be the main cylinder/booster block assembly has died but normally this would come up as a fault and the ABS warning light should come on.

Tell me about it
Not having done any system like this leaves me a little in the dark experience wise.
Could you possibly help with:
Pedal travel - in 'normal 'operation AND when bleeding the pedal will only travel 1-2 inches then is solid. Is this as is ?
Front lower nipples- (hydrostatic circuit) I can't get any fluid to flow at all ?

Am confused a little with your explanation
You say ' bleed hydrostatic circuit first' then later 'Last operation ,bleed hydrostatic circuit calipers'
Are these one and the same i.e. do twice ?

Have done blink test and only getting sensor faults


.

chrisrr said:

Tell me about it
Not having done any system like this leaves me a little in the dark experience wise.
Could you possibly help with:
Pedal travel - in 'normal 'operation AND when bleeding the pedal will only travel 1-2 inches then is solid. Is this as is ?
Front lower nipples- (hydrostatic circuit) I can't get any fluid to flow at all ?

Am confused a little with your explanation
You say ' bleed hydrostatic circuit first' then later 'Last operation ,bleed hydrostatic circuit calipers'
Are these one and the same i.e. do twice ?

Have done blink test and only getting sensor faults

Click to expand...

I know what you mean. I just gave you a shortened version of the recommended method direct from the genuine workshop manual.

Having looked at the ABS operation diagram it occurs to me that there are only a limited number of possibilities here.

It sounds like the power circuit is O.K. so the hydrostatic circuit is the issue.

Breaking that down, the problem could be the master cylinder, possibly the tilt valve is stuck so fluid is not entering from the reservoir.

The next possibility is stuck servo valves. The hydrostatic fluid pressure from the master cylinder is transferred to the servo valves and from there directly to the lower caliper pistons. The servo valves also allow the return of fluid back to the reservoir.

The last possibility (unlikely) is that the lower pistons in both front calipers are seized so no fluid is flowing.

The bad news is that as far as I know, if the problem is the master cylinder or servo valves you cannot repair them as there are no service parts available. Any problems in the unit and the whole thing has to be replaced (or at least that's what the manual says). You need to buy a new master cylinder and booster valve assembly (very expensive!) or at least get a good second hand one (they do come up).

It may be worthwhile checking for seized pistons, it may be a long shot but if it is this then it is an easier and much cheaper fix. Perhaps you could consider removing the front calipers and checking the pistons are free to move, or better still, remove the pistons and replace the seals (and pistons if corroded) then check for correct operation using compressed air (TAKE CARE when using compressed air, only small pressure is needed).

One other thought, and I'm sure you have checked this - are the bleed nipples clean and clear? If the bleed nipples are blocked you will not see fluid coming out. Maybe remove the bleed nipples and clean them through to be absolutely sure.

Whatever the cause of the problem, DO NOT DRIVE until the brakes are working properly.

HTH

I suppose I knew it was going to something pretty more serious than normal .
Pistons are free,as are nipples .To check not a caliper blockage I released feed pipes and used the top caliper on the bottom and got a flow .No flow from released bottom feed pipe .
The diagram you speak of is this from the LR service manual ? Might need to get one - cheeky question ,any chance of a scan for the short term? just the dia.of course
Helping lots ,Thanks