Disco 1 The mysterious pressure reducing brake valve.

findo1 · Thursday at 08:39

I am restoring a 30 year old disco 1 and decided to replace all the brake components. When I tried to bleed the brakes no fluid would pass to the rear brakes. I swapped the new pressure valve for my 30 year old valve and got a working system. When i looked at the new valve it was blocked at the rear brake pipe inlet and outlet. So i contacted the supplier and received this reply from their "technical guy"

"Im sorry to hear you are having issues bleeding your brakes, please could you tell me if you are bleeding the system with all four wheels on the ground to ensure there is load on the suspension?
Typically the bias/compensator valve will not allow fluid into the rear brakes unless the suspension is under load by having the weight of the vehicle on the wheels"

findo1 · Thursday at 08:59

findo1 said:
I am restoring a 30 year old disco 1 and decided to replace all the brake components. When I tried to bleed the brakes no fluid would pass to the rear brakes. I swapped the new pressure valve for my 30 year old valve and got a working system. When i looked at the new valve it was blocked at the rear brake pipe inlet and outlet. So i contacted the supplier and received this reply from their "technical guy"
"Im sorry to hear you are having issues bleeding your brakes, please could you tell me if you are bleeding the system with all four wheels on the ground to ensure there is load on the suspension?
Typically the bias/compensator valve will not allow fluid into the rear brakes unless the suspension is under load by having the weight of the vehicle on the wheels"

So I went back into the garage and changed over the valves (spilled fluid all over the floor me, and the disco) and attempted to bleed the brakes again "with all four wheels on the ground" ,and guess what?..... The valve is still blocked and with no fluid going to the back brakes. So here's the question
Does the vehicle need to have weight on the axles ,"load on the suspension" ,all four wheels on the ground" for that brake valve to work.?

GRATCH · Thursday at 09:20

It's not a load compensating valve, so no.

Is the blockage an undrilled hole or something else inside?

If the old one works and the new direct replacement one doesn't, that suggests the new valve is faulty.

I'd suggest that Sammy has no technical skills, which is why they work in the returns department.

findo1 · Thursday at 09:46

GRATCH said:
It's not a load compensating valve, so no.

Is the blockage an undrilled hole or something else inside?

If the old one works and the new direct replacement one doesn't, that suggests the new valve is faulty.

I'd suggest that Sammy has no technical skills, which is why they work in the returns department.

Thank you I didn't share my own thoughts but knew it was a fools errand I was sent on (to try with the wheels on)
I was wondering if i should apply for a job there as it seems they have a need for someone who has a clue about land rovers.
Im told there is a piston inside the valve which shuttles between the front and back brake inlet/outlet depending on pressure. It would appear that this piston is stuck blocking the rear inlet/outlet. I can see it covers both.

Anaconda · Thursday at 10:18

Does the valve not move back and forth under gravity to stop the rears locking up so easily?
(When you brake hard)

Pawl · Thursday at 10:33

Anaconda, I think you're referring to a "G" sensing valve. I don't think Discovery ever had one.
I think the D1 has a pressure proportioning valve which should let low pressure through without restriction (also allowing easy bleeding) and then it only allows a proportion of the pressure through at higher pressures - to ensure the rear wheels don't lock-up before the front wheels.

findo1 · Thursday at 10:45

Anaconda said:
Does the valve not move back and forth under gravity to stop the rears locking up so easily?
(When you brake hard)

I did try giving it a thump on the bench but that piston is stuck solid. You could say it does its job because the back will never lock up.I cant tell if the tech guy is confused, ignorant, or just trying to justify his position by sounding clever.

findo1 · Thursday at 11:38

Thanks guys, Im yet to resolve this with the seller so I removed the original email from "sammy" which showed the company name. Its always stressful dealing with returns (for some reason) .

Anaconda · Thursday at 13:16

Pawl said:
Anaconda, I think you're referring to a "G" sensing valve. I don't think Discovery ever had one.
I think the D1 has a pressure proportioning valve which should let low pressure through without restriction (also allowing easy bleeding) and then it only allows a proportion of the pressure through at higher pressures - to ensure the rear wheels don't lock-up before the front wheels.

Stand corrected I mistakenly presumed it was the same item.

landowner · Thursday at 14:45

The old Minis used to have a similar valve, sometimes had to pipe it up so as to blow the shuttle back from one side to near the centre before bleeding

discool · Thursday at 16:52

Rubbish but perhaps he thinks you have D1 with air suspension or supplied the wrong item

Did they ask the model year of your vehicle and if it had ABS or not.

If you have a 200 series D1 and which is RHD then the pt number for a pressure control release valve is NTC 6868L although I expect thats been superseded by now.

For the RHD 300 series non ABS the pt number is ANR3149.

discool · Thursday at 17:01

findo1 said:
I did try giving it a thump on the bench but that piston is stuck solid. You could say it does its job because the back will never lock up.I cant tell if the tech guy is confused, ignorant, or just trying to justify his position by sounding clever.

Of course as you know all four wheels can lock-up, and even if fitted with ABS if the conditions are right

findo1 · Thursday at 19:59

landowner said:
The old Minis used to have a similar valve, sometimes had to pipe it up so as to blow the shuttle back from one side to near the centre before bleeding

I could see that alright. You've actually got me thinking, in the picture in one of the outlets is a blank thats screwed in, perhaps you block off the front inlet and connect the rear, to pipe it up ?Anyhow this ones blocked It wont let any fluid in or out .Surely you cant have the shuttle able to close off the rear brake line? IDK Id also be a bit worried that i could lose the rear brakes altogether even if i could pipe it up now .(which I cant)
PS that blank is actually to block off the second front brake outlet in a defender 90.So forget that.

findo1 · Thursday at 20:12

discool said:
Rubbish but perhaps he thinks you have D1 with air suspension or supplied the wrong item

Did they ask the model year of your vehicle and if it had ABS or not ?

If you have a 200 series D1 and which is RHD then the pt number for a pressure control release valve is NTC 6868L although I expect thats been superseded by now.

For the RHD 300 series non ABS the pt number is ANR3191.

They ask for the VIN number so no excuses. But It must be a difficult job knowing the parts for all the models spanning decades. Ill let you know how I get on I'm a veteran at this I once got a refund from Paddocks!

landowner · Thursday at 20:48

findo1 said:
I could see that alright. You've actually got me thinking, in the picture in one of the outlets is a blank thats screwed in, perhaps you block off the front inlet and connect the rear, to pipe it up ?Anyhow this ones blocked It wont let any fluid in or out .Surely you cant have the shuttle able to close off the rear brake line? IDK Id also be a bit worried that i could lose the rear brakes altogether even if i could pipe it up now .(which I cant)

Its in case of a fluid leak, leak at back would allow piston to be forced over and block exit, same if front had a leak

findo1 · Thursday at 21:18

landowner said:
Its in case of a fluid leak, leak at back would allow piston to be forced over and block exit, same if front had a leak

Single line? Sounds like a similar valve but not exact. As the piston in this valve blocks the inlet before the oulet (which are offset) However, If i turned it upside down and made the outlet the inlet and blocked the front inlet and just pushed fluid in that way I imagine that shuttle would be pushed up that cylinder. Thanks for the info. Food for thought .But still don't think i want a valve that prevents fluid getting to the brakes.

discool · Thursday at 21:22

We i’m surprised on Paddocks making an error, I expect they have access to a parts catalogue online in one format or the other just like Rimmer's do, the main dealer parts dept always has way done with their Microfiche slides.

Anyway the valve has three pipe connections , so from the master cylinder to the valve and onwards to front caliper secondary circuit and then to the rear brakes.

I’ve only had to change pads and fluid in must have a look on Saturday to see if I’m correct …or not.

May help you: https://rimmerbros.com/images/pdfs/discovery.pdf

landowner · Thursday at 21:28

findo1 said:
Single line?

Think Mini had both single and dual on a diverent shuttle valve , the also had a pressure reduction valve at back

findo1 · Thursday at 21:49

discool said:
We i’m surprised on Paddocks making an error, I expect they have access to a parts catalogue online in one format or the other just like Rimmer's do, the main dealer parts dept always has way done with their Microfiche slides.

Anyway the valve has three pipe connections , so from the master cylinder to the valve and onwards to the (secondary) circuit caliper piston, and then finely a pipe from the bottom end of the valve ( your pic shows a blanking plug) going to the rear brakes. Thats how I read it as I've only had to change pads and fluid in the years I’ve owned my D1, must have a look on Saturday to see if I’m correct …or not.

May help you: https://rimmerbros.com/images/pdfs/discovery.pdf

I had a tustle with them a few years back. Worst customer service i've ever had ,told me they were busy and i should stop bothering them when i enquired repeatedly how my return request was getting on, seriously, couldn't believe it.I don't go near them now. Mike from Brittania Restorations did a video about it, as i was asking him for his advice about a pair of swivels Id bought which were obviously machined wrong and the bearings would fall out when you tried to fit them!I sent them a video . .He couldn't believe their attitude either. They didn't argue technicalities they just kept saying "they were dealing with it now f off" basically. Had to threaten them with the bank in the end.I posted on a land rover page "has anyone had bother with Paddocks" ,and got the first reply in about a minute, (i kid you not)several people had just given up trying. Some thought id never get a refund. Some thought it was a policy. Any way Im over it now(reaches for whisky bottle)

landowner · Thursday at 22:21

findo1 said:
Single line? Sounds like a similar valve but not exact. As the piston in this valve blocks the inlet before the oulet (which are offset) However, If i turned it upside down and made the outlet the inlet and blocked the front inlet and just pushed fluid in that way I imagine that shuttle would be pushed up that cylinder. Thanks for the info. Food for thought .But still don't think i want a valve that prevents fluid getting to the brakes.

They were useless anyway, usually seized, I never had one that worked and I must have had a dozen Minis over the years, many parts shared with land rover

Disco 1 The mysterious pressure reducing brake valve.

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