I'm in the process of rebuilding a (non-North American) 1989 BJ60. The vehicle was originally equipped with drum brakes on all wheels, so never came with a brake proportioning valve. I am adding a year-correct, factory original brake master cylinder, dual-diaphragm booster and proportioning valve. I am interested in how the valve works.
This is the type of valve which sits below the brake master cylinder and only functions to bias the proportioning during hard braking to reduce the fluid pressure in the rear brake circuit. I am not talking about the load-sensing proportioning valve which sits on the rear axle on (I think) US-market FJ62s (and others).
There are at least five different proportioning valves which were fitted (across all markets) to 60s over the years; 47190-14020, 47190-30030, 47190-60010, 47190-60020 and 47190-60030.
Mine is the latest iteration and came on lower-spec 1987-89 60s. For an in-situ picture, see this thread.
Taking the valve apart (27 mm socket on the end plug and a tap with a hammer and 12 mm socket on the back of the piston to free it), it was full of some brake fluid/dirt residue:
After cleaning:
We have (left to right on the above picture):
-'piston seal' (this is strangely shaped with a textured face)
-shaft (blue)
-spring
-1/2" O-ring
-piston (gold)
-9/16" O-ring
-U-cup seal
-End plug.
My questions are (i) how does the valve operate? and (ii) which circuit if front and which is rear?
I have made a fairly accurate cross-sectional diagram:
I have indicated input and output ports (with arrows) and am certain of this much. The end plug is shaded lilac and the two seals and two o-rings are shown. I've drawn the valve in the resting position with the gold piston resting on the end plug.
Note that there is no seal between the left and right sections of the valve (the blue shaft is significantly undersized compared to the inner bore diameter of the gold piston).
I'm also confused by the textured 'piston seal' which sits in the bore exactly where the left hand fluid outlet is. Is this some sort of baffle to delay the fluid reaching the front brake system (to give the rear shoes a chance to contact the drums just before the front pads meet the discs?
I've tried reading articles online, but they never cover this simple type of valve. I can't get my head around it.
I would really appreciate a technical explanation if anyone knows!
Thanks
EO
This is the type of valve which sits below the brake master cylinder and only functions to bias the proportioning during hard braking to reduce the fluid pressure in the rear brake circuit. I am not talking about the load-sensing proportioning valve which sits on the rear axle on (I think) US-market FJ62s (and others).
There are at least five different proportioning valves which were fitted (across all markets) to 60s over the years; 47190-14020, 47190-30030, 47190-60010, 47190-60020 and 47190-60030.
Mine is the latest iteration and came on lower-spec 1987-89 60s. For an in-situ picture, see this thread.
Taking the valve apart (27 mm socket on the end plug and a tap with a hammer and 12 mm socket on the back of the piston to free it), it was full of some brake fluid/dirt residue:
After cleaning:
We have (left to right on the above picture):
-'piston seal' (this is strangely shaped with a textured face)
-shaft (blue)
-spring
-1/2" O-ring
-piston (gold)
-9/16" O-ring
-U-cup seal
-End plug.
My questions are (i) how does the valve operate? and (ii) which circuit if front and which is rear?
I have made a fairly accurate cross-sectional diagram:
I have indicated input and output ports (with arrows) and am certain of this much. The end plug is shaded lilac and the two seals and two o-rings are shown. I've drawn the valve in the resting position with the gold piston resting on the end plug.
Note that there is no seal between the left and right sections of the valve (the blue shaft is significantly undersized compared to the inner bore diameter of the gold piston).
I'm also confused by the textured 'piston seal' which sits in the bore exactly where the left hand fluid outlet is. Is this some sort of baffle to delay the fluid reaching the front brake system (to give the rear shoes a chance to contact the drums just before the front pads meet the discs?
I've tried reading articles online, but they never cover this simple type of valve. I can't get my head around it.
I would really appreciate a technical explanation if anyone knows!
Thanks
EO
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