Rear Load Proportioning Valve stuck... or is it???

solvemon · 2019-05-11 08:57:03

So in my MOT (or the equivalent here in Norway) my 2005 Scudo JTD 2.0 got a few remarks, among them: stuck load proportioning valve. After getting it up on my ramps, and giving it a good splash of WD-40, and banging it with the hammer for a while, I can actually move it by wedging a screw-driver into the "arm" and levering it open. It feels quite smooth in that the motion is not jerky or stuck in any way, but I have to put a fair amount of power to counter the spring.

To be honest, I don't know a lot about this part, so I'm not even sure what it's supposed to look like "at rest", when the brakes are not pressed? Because mine is in the complete "home" or closed position. This is also the case when I jacked the van up off the back wheels. Is this to be expected? Furthermore, when I had a helper press the brakes for me (with the engine running), I can see the arm moving but veeeeeery little, maybe 2-3 mm at the most. Is this as expected, or could something else be preventing the arm from opening?

Some pictures for your ocular pleasure

Thanks in advance guys!

ruston · 2019-05-11 19:54:00

The valve doesn't have much movement anyway, especially in a lightly loaded vehicle, which is why they seize up in the first place. As long as there is some movement when the pedal is pressed then all should be fine.

steve the grease · 2019-05-12 18:54:52

The valve isn't supposed to move when you press the pedal. The idea is to cut the pressure to the rear brakes when the van is lightly loaded, to stop the brakes locking. When the van is laden ( rear suspension lower) more pressure is allowed to the brakes. Give the valve a good lube and wire brush every service / time you are underneath.

solvemon · 2019-05-13 05:49:46

Thanks a lot for the the replies guys, in that case I should be good! When I get around to the other small issues I have I'll take it back in and report back!

ginger chips · 2019-08-26 15:51:37

anyone with a spare valve for sale or just the pressed steel lever for the rear brake compensator valve.please

TheCrimsonBadger · 2019-11-14 19:40:23

https://rover.ebay.com/rover/0/0/0?mpre … 4363318023 I’ve bought that and works for me

OAT · 2019-11-15 00:27:56

I had continuous problems with mine. Nothing at all aparent in use, not even when emergency braking under heavy or light loading.

But had problems getting it through mot's due to uneaqual braking. Never got to the bottom of it even after 2 different pro (?) mechanics had a go and couldn't identify any fault.

Replaced it this year. Expensive at about £65.

woodbine · 2019-11-18 20:04:42

I've heard of brake compensators like the one on the inner wing of my early Carlton, but never heard of an LPV that actually varies rear braking pressure due to pressure on a lever according to load carried. I do some of my own maintenance, and as I didn't know this valve existed, it sounds like it needs lubricating.

I very rarely carry heavy loads, so I suppose that the valve hasn't had a lot of use. Bearing in mind that I have owned my van for over 12 years and never paid the LPV any attention - will it still be OK? Or am I worrying about nothing and if it passes the MOT every year it must be OK?

Last edited by woodbine (2019-11-19 20:11:20)

OAT · 2019-11-18 23:56:00

woodbine wrote:

I very rarely carry heavy loads, so I suppose that the valve hasn't had a lot of use. Bearing in mind that I have owned my van for over 12 years and never paid the LPV any attention - will it still be OK? Or am I worrying about nothing and if it passes the MOT every year it must be OK?

When mine failed its mot I was told that the difference in load proportioning was 80% / 20% when I think the max allowable difference was 20%.
Don't quote me on the numbers but it was obviously quite bad. They suggested even dangerous and that I would suffer from uneven braking in an emergancy stop. However in use over 25,000 miles I never had a problem. Loaded or light.

On three different occasions I had it inspected and lubed with no detectable faults, but it still failed mot 2 years running. (there are of course, other mot testing stations available. wink ) When I finally had it replaced it it resembled an undefined lump of rusty slag.

I don't understand it's operation but think it optimises braking force between front or rear axels depending on rear loading. (A bit like when I used to put a bag of cement in the back of my Reliant Regal Van when empty. smile ) I don't think the mechanics who checked it understood it properly either.

So for me, yes, a knackered one was ok so long as I could get an mot.

Mind you, it is possible that anyone brought up on anti lock might have more of a problem. Anyone familier with the braking on almost any vehicle pre 80's should be ok. We only had manual load ballanceing via the handbrake then. smile

vaz2121 · 2019-11-19 00:41:03

Rather than just repeat the same explanation that's already been given.........
Notice how most cars vans get black/dirty (Brake dust) front wheels and the rears stay fairly clean even when fitted with rear discs ..............
(load proportioning valve) This is a reason why ............

If it passes MOT and it's knackered ............... Fine............

Ive tended to notice MOTer's giving it a wiggle to see if it's free ...........
(Maybe it's because they know we'd load them up) ..........

steve the grease · 2019-11-20 15:00:18

OAT wrote:

woodbine wrote:
I very rarely carry heavy loads, so I suppose that the valve hasn't had a lot of use. Bearing in mind that I have owned my van for over 12 years and never paid the LPV any attention - will it still be OK? Or am I worrying about nothing and if it passes the MOT every year it must be OK?
When mine failed its mot I was told that the difference in load proportioning was 80% / 20% when I think the max allowable difference was 20%.
Don't quote me on the numbers but it was obviously quite bad. They suggested even dangerous and that I would suffer from uneven braking in an emergancy stop. However in use over 25,000 miles I never had a problem. Loaded or light.
On three different occasions I had it inspected and lubed with no detectable faults, but it still failed mot 2 years running. (there are of course, other mot testing stations available. ) When I finally had it replaced it it resembled an undefined lump of rusty slag.
I don't understand it's operation but think it optimises braking force between front or rear axels depending on rear loading. (A bit like when I used to put a bag of cement in the back of my Reliant Regal Van when empty. ) I don't think the mechanics who checked it understood it properly either.
So for me, yes, a knackered one was ok so long as I could get an mot.
Mind you, it is possible that anyone brought up on anti lock might have more of a problem. Anyone familier with the braking on almost any vehicle pre 80's should be ok. We only had manual load ballanceing via the handbrake then.

The pressure in a hydraulic system should be the same everywhere ( like current in a circuit) so either one of the little valves in the load valve was stuck down ( not very common) ... or some fluid was leaking out of the wheel cylinder on one side wetting the shoe and reducing efficiency or wheel cylinder siezed. Both last two common problems with rear drum brakes.

OAT · 2019-11-20 23:48:29

steve the grease wrote:

The pressure in a hydraulic system should be the same everywhere ( like current in a circuit) so either one of the little valves in the load valve was stuck down ( not very common) ... or some fluid was leaking out of the wheel cylinder on one side wetting the shoe and reducing efficiency or wheel cylinder siezed. Both last two common problems with rear drum brakes.

I suspect it was indeed an internal valve stuck. No other faults could be found in the braking system.

Still not understanding this fully though.

Wouldn't the hydraulic pressure be the same everywhere without the assistance of a proportioning valve? Doesn't the load proportioning valve increase pressure in the line to the heaviest loaded axel (or more likely reduce it to the lightest)?

steve the grease · 2019-11-21 02:45:18

Because of inertia, a lot of the weight of a vehicle will transfer to the front wheels under heavy braking. This means that the rear of the vehicle will tend to rise and eventually skid. The idea of of the valve is to cut brake pressure as the suspension rises , to stop skiding, the more heavily laden the van is the less the rear rises and so more of the pressure is allowed through to the rear brakes.

vaz2121 · 2019-11-21 04:00:16

steve the grease wrote:

Because of inertia, a lot of the weight of a vehicle will transfer to the front wheels under heavy braking. This means that the rear of the vehicle will tend to rise and eventually skid. The idea of of the valve is to cut brake pressure as the suspension rises , to stop skiding, the more heavily laden the van is the less the rear rises and so more of the pressure is allowed through to the rear brakes.

What he said

big_smile

OAT · 2019-11-21 11:46:42

I was thinking it pre set according to the weight on the axels. But it is actively adjusts to suit the changing loading during braking.

I see now thanks.

cliffo · 2020-05-15 07:26:37

Has anyone any advice about how to adjust these compensators? I'm just taking the leaky air suspension off SteVan and replacing with springs. I suspect that the ride height will be a lot taller so may need to adjust this

vaz2121 · 2020-05-15 10:56:46

cliffo wrote:

Has anyone any advice about how to adjust these compensators? I'm just taking the leaky air suspension off SteVan and replacing with springs. I suspect that the ride height will be a lot taller so may need to adjust this

I can understand your dilemma But as you say if ride height is way out of whack............
In the very first photo on this post it shows this valve and spring is mounted on a threaded rod ............
I have No idea what the length - Ride height or where to find these measurements ...........
That's if any adjustment was needed on fitting Air Bags...........

My worry would be more likely the replacement valve set up {probably seized because} as Air ride is all but self leveling and shows little in the way of spring droop if at all even loaded

But then I dear say you'll dicover what/which

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#1 2019-05-11 08:57:03

Rear Load Proportioning Valve stuck... or is it???

#2 2019-05-11 19:54:00

Re: Rear Load Proportioning Valve stuck... or is it???

#3 2019-05-12 18:54:52

Re: Rear Load Proportioning Valve stuck... or is it???

#4 2019-05-13 05:49:46

Re: Rear Load Proportioning Valve stuck... or is it???

#5 2019-08-26 15:51:37

Re: Rear Load Proportioning Valve stuck... or is it???

#6 2019-11-14 19:40:23

Re: Rear Load Proportioning Valve stuck... or is it???

#7 2019-11-15 00:27:56

Re: Rear Load Proportioning Valve stuck... or is it???

#8 2019-11-18 20:04:42

Re: Rear Load Proportioning Valve stuck... or is it???

#9 2019-11-18 23:56:00

Re: Rear Load Proportioning Valve stuck... or is it???

#10 2019-11-19 00:41:03

Re: Rear Load Proportioning Valve stuck... or is it???

#11 2019-11-20 15:00:18

Re: Rear Load Proportioning Valve stuck... or is it???

#12 2019-11-20 23:48:29

Re: Rear Load Proportioning Valve stuck... or is it???

#13 2019-11-21 02:45:18

Re: Rear Load Proportioning Valve stuck... or is it???

#14 2019-11-21 04:00:16

Re: Rear Load Proportioning Valve stuck... or is it???

#15 2019-11-21 11:46:42

Re: Rear Load Proportioning Valve stuck... or is it???

#16 2020-05-15 07:26:37

Re: Rear Load Proportioning Valve stuck... or is it???

#17 2020-05-15 10:56:46

Re: Rear Load Proportioning Valve stuck... or is it???

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