Overhaul of brake proportioning valve?

[Flying Torquewrench]

MOT time yesterday and it failed on the rear brakes not achieving enough pressure. Front brakes are absolutely fine.

No matter how much pressure is applied to the brake pedal it only just stops the rear wheels from turning. I wonder if the brake proportioning valve on top of the rear axle is playing up. Having done a bit of research on the internet a new one is around £400-£500 pounds.

In the end we managed to get the Patrol through the MOT but it only just touches the green section on the measuring equipment. Not ideal when most of the time I am towing near max capacity and therefore would like my brakes to work properly. I know that a pass is enough but I am relying more on the front brakes to stop nearly 6 tonnes.

Before buying a new proportioning valve I wonder if anybody has taken one apart and if it can be cleaned up inside. It is a piston that moves side to side and after 22 years is probably a bit tatty on the inside. I asked ‘my’ mechanic and he discourages it and will only replace the valve in its entirety.

Any ideas/advice?

 

[solarman216]

Take it off and bin it, I have and brakes are much better, remove all the bracketry and it will look like it was never there, Rick

 

[Banshee]

MOT time yesterday and it failed on the rear brakes not achieving enough pressure. Front brakes are absolutely fine.

No matter how much pressure is applied to the brake pedal it only just stops the rear wheels from turning. I wonder if the brake proportioning valve on top of the rear axle is playing up. Having done a bit of research on the internet a new one is around £400-£500 pounds.

In the end we managed to get the Patrol through the MOT but it only just touches the green section on the measuring equipment. Not ideal when most of the time I am towing near max capacity and therefore would like my brakes to work properly. I know that a pass is enough but I am relying more on the front brakes to stop nearly 6 tonnes.

Before buying a new proportioning valve I wonder if anybody has taken one apart and if it can be cleaned up inside. It is a piston that moves side to side and after 22 years is probably a bit tatty on the inside. I asked ‘my’ mechanic and he discourages it and will only replace the valve in its entirety.

Any ideas/advice?

I had one of these on my Maverick and was reluctant to remove it due to me being of the belief that Nissan put it there for a reason, but I'll be honest, my rear braking efficiency on the rear improved no end!!!

There isn't one at all on my 2004 Terrano and I've not looked under my 98 Patrol yet but I suspect there might be if your later Patrol has one :nenau

There's no way I'd spend £500 on one though, plus I'm sure if it's not there your MOT tester can't mark you down for it as you can't test something that isn't there :naughty

 

[Wallace]

Are the rear brakes discs or drums and are they working correctly? I would give the rear brakes an inspection/service then check the proportioning valve operation.

With the valve removed you can end up with too much rear braking and that's not fun in an emergency stop when the rear locks before the front.

 

[Wallace]

There isn't one at all on my 2004 Terrano

It's here under the bonnet disguised as an ABS pump.

 

[Flying Torquewrench]

Thank you all!

It has brake discs and the brakes have been checked and all works fine. Rear callipers are only 2 years old and in a very good state.

I will bypass the valve and see what that gives me. The plan is to remove the Patrol from service next year, hence why I am reluctant to spend a lot of money on her.

 

[Wallace]

If you bypass the valve, take it out on a deserted wet road and try a few emergency stops to see what the rear end does. It may be fantastic on dry tarmac and lethal in the wet.

 

[Flying Torquewrench]

Don’t worry Wallace, it will be tested. :thumb2 I will satisfy myself that the behaviour of the car without the proportioning valve is still safe.

However I don’t believe that Rick and Banshee would take a deathtrap on the road.

 

[Banshee]

Don’t worry Wallace, it will be tested. :thumb2 I will satisfy myself that the behaviour of the car without the proportioning valve is still safe.

However I don’t believe that Rick and Banshee would take deathtrap on the road.

I try to keep mine as safe as possible, if I thought something was going to endanger life then I wouldn't take it out before it was fixed right.

My Maverick seemed to pull up a lot quicker once that brake bias valve was binned.

 

[elty001]

Not sure about the patrol but they where hit and miss with which models of terrano had them fitted.
My 98 abs terrano had one but my 2000 abs terrano hasn't.
While my 96 non abs had one my 97 non abs didn't.
Not sure if the ones without have had them removed prior to my ownership but the only one that used to lock up bad was the non abs 96 with one fitted.

 

[Barrbeast]

All the proportion valve does is vary the braking based on the rear axle load (less load, less rear braking). Without it there, I would have thought the rear brakes should just operate at full capacity

 

[solarman216]

A while ago I fitted new discs and pads all round and with the valve fitted and always a fully loaded motor the rear disks were rusting, only lightly but it proved they were not working very hard, the valve when I removed it was not seized, after it was gone brakes were much much better, and now for a while I am running almost empty with no rear lock up problems at all, and disks are rust free, Rick

 

[Wallace]

All the proportion valve does is vary the braking based on the rear axle load (less load, less rear braking). Without it there, I would have thought the rear brakes should just operate at full capacity

Exactly this on both points. Add longer springs and the valve has no chance of working.

 

[Flying Torquewrench]

I need to get some new brake pipe and than the valve will be removed in the next couple of weeks. :thumb2

 

[Barrbeast]

Exactly this on both points. Add longer springs and the valve has no chance of working.

That's why it's recommended to fit an extension to the the bracket on the rear axle to raise it by the same as the lift

 

[Flying Torquewrench]

Started the removal of the brake proportioning valve today.

First the removal of the bracket from the axle.

 

[Flying Torquewrench]

The first brake pipe came off quite easily but the rest didn’t want to budge. Not the best access either.

 

[Flying Torquewrench]

In the end I cut the pipes near the crossmember and pulled the valve out.

Installing a T piece to go from 2 brake pipes to one but that has to wait till tomorrow.

 

[macabethiel]

Buy an adjustable brake balancer valve they are not expensive

If you do not have dual circuit brakes you can buy adjustable balancer valves you just tweak them until the rear brakes do not lock.

I fitted one to my old Austin Mini when I changed the size of the rear wheel cylinders. There are loads out there.

https://www.ebay.co.uk/itm/1X-Brake...903409?hash=item2af61081f1:g:fUkAAOSwjVtfnzKx

 

[Flying Torquewrench]

Thanks Ted, I will have a look. Will initially just use it without the brake portioning valve and see how it behaves. Another valve is quickly installed if required.