Patrol 4x4 - Nissan Patrol Forum banner
1 - 10 of 10 Posts

· Registered
1988 MK260 SD33T
Joined
·
15 Posts
Discussion Starter · #1 ·
Hey guys! So I'm having serious braking problems.

If I give my brakes any more than light, even pressure, the rear wheels lock up. From what I can find this usually means proportioning valve issues, and when I looked at my valve, it's condition seems to support this theory.

My problem is I can't find any parts or relevant material for this specific valve. It's like it doesn't exist. All other valves are "load sensing" and connect to the rear axle whereas mine is only bolted to the frame without a spring.

If any of y'all have some advice or can help me identify this part I'd appreciate it.

Bedrock Wood Automotive tire Grey Wall
 

· Registered
1988 MK260 SD33T
Joined
·
15 Posts
Discussion Starter · #2 ·
Well update (sort of)
I found a diagram with my part listed as "Brake Power Regulator" or just "Valve Assembly".
Though all websites have it listed as not available or want a ridiculous amount.
Part number appears to be 46400C7910 or 46400C7911
Organism Font Handwriting Parallel Art
 

· Administrator
Y2KGUII ZD Wgn
Joined
·
56,309 Posts
I don't know much about them, but I often here this place named by OS members.
 

· Administrator
Y2KGUII ZD Wgn
Joined
·
56,309 Posts
Load sensing or brake proportioning valve is the same thing
Maybe so, but, what he has operates on a totally different system that is why he is asking us the question.
 

· Rust is just natural weight reduction.
1986 SD33T SWB
Joined
·
11,505 Posts
To my understanding, its not really a load sensing valve in the sense that it adjusts front vs rear brake bias with increasing/decreasing load, it just regulates front vs rear brake line pressure. Early MQ without them had a habit of locking rear brakes when unladen and heavy braking.

I suspect that dark staining on yours is slight weep, which will reduce effective pressure in the part of the valve that regulates rear brake pressure, allowing more fluid to pass, hence the locking.

I've never pulled one apart, but there will be a gasket or O ring or something that holds the front and rear sections together, you could try replacing that for a quick fix, or just replace the whole thing with an aftermarket adjustable proportioning valve.

Here is a diagram of how it works. I suspect the weep is likely somewhere around the chamber the springs act in.

Motor vehicle Font Parallel Auto part Engineering
 
  • Like
Reactions: geeyoutoo

· Rust is just natural weight reduction.
1986 SD33T SWB
Joined
·
11,505 Posts
Also if you have recently replaced your wheel cylinders or master cylinder, ensure it is the same as what came off.
At least in AU, where we didn't have that valve on early cars, there were 2 different master cylinder and wheel cylinder bore sizes.

Early cars, without that valve, 23.8mm bore master cyl and 19.05mm wheel cyl.
Later cars, with the valve, 25.4mm bore master and 22.22mm wheel cyl.
Front caliper size didn't change, so a mismatch in master/wheel cyl will affect rear more than front.
 
  • Like
Reactions: geeyoutoo

· Registered
Joined
·
70 Posts
I don’t have much info on the valve but it isn’t the same as in the manual James mentioned. The number of connected lines is different.

Try to purge the brake circuit or take it apart. But for safety issues, perhaps it´s better to replace it.
 

· Registered
Nissan patrol w160
Joined
·
2 Posts
This reacts on the retardation of the car.the steelball in the rear ov the valve reduce or open for brake fluid. I had/or have the same problem. Tok it apart and cleaned it, changed some o-rings. Put it back together. Worked perfekt. I think the today's brake fluids is not compatible with these old cars and systems.
 
1 - 10 of 10 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top