Brake proportioning valve - how does it work? (1 Viewer)

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Eurasiaoverland

Eurasiaoverland

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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:


20230730_133700.jpg


After cleaning:

20230802_194310.jpg


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:

20230802_205617.jpg


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
 
Last edited:
Superb question.. well asked and love the disassembly photos and reverse engineered diagram! Following.
 
2mbb said:
This might help:

Click to expand...

Thank you very much indeed! That explains it clearly and answers all my questions. What a great resource.

I see where I was getting confused now - I did not realise the valve had two functions and was trying to integrate both into a proportioning function. It's all very clear now.

As the Wilwood website says: "The inner workings of ... [a] proportioning valve are relatively simple but deceptively complex"

Thanks again, I learned a lot from that document. Is there an index of various training sheets? I can't think of anything else that mystifies me on the vehicle, but I'm sure I could learn more.

EO
 
duncanrm said:
Superb question.. well asked and love the disassembly photos and reverse engineered diagram! Following.
Click to expand...

Thanks Duncan!

So from reading the above linked document from 2mbb, and referring back to my diagram (just for anyone who doesn't want to read through the linked pdf, or in case the link goes bad):

20230802_205617.jpg


The proportioning valve is in blue and the left hand circuit is the rear brake crcuit. The 'piston seal' can allow fluid past into the rear brake output port, but under hard braking, the back-pressure from the wheel cylinders will cause the seal to push back on the blue proportioning valve, move it to the right against the spring tension, and momentarily restrict the output, until the back pressure reduces and the spring re-opens the port. This is why the 'piston seal' has an odd shape and is axially loose on the blue valve.

The gold piece is the bypass valve and has nothing to do with proportioning. If the front brake pressure drops significantly below the rear brake pressure, the gold valve will move to the left, over-riding the proportioning function.

In other word, all being well, the proportioning function will stop your rear wheels locking up under heavy braking, unless the front circuit fails, in which case it will do everything it can to make your rear wheels lock up!

EO
 
Eurasiaoverland said:
In other word, all being well, the proportioning function will stop your rear wheels locking up under heavy braking, unless the front circuit fails, in which case it will do everything it can to make your rear wheels lock up!
Click to expand...

Thats my reading too... its such a clever design that I'm now considering adding one to my HJ47 (rear drums, retrofitted front discs, no prop. valve)
 
duncanrm said:
Thats my reading too... its such a clever design that I'm now considering adding one to my HJ47 (rear drums, retrofitted front discs, no prop. valve)
Click to expand...

Elegant indeed! Good luck finding one. I got two, when I took them apart, in both case the bypass valve was welded to the internal bore of the valve with brake fluid residue so as to hold the (not insignificant) spring tension without the end cap being on. The one pictured just needed a hammer tap to free it and cleaned up well (the rubber bits look to be in pretty good shape too), but the other, which had rust, I hammered until the anodising on the proportioning valve came off and is still seized (and going in the bin).

These seem to act as something of a filter so important to keep clean brake fluid. They also have no bleed or drain valve.

CityRacer in the US do a faithful reproduction of two different 40 Series valves.

EO
 
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duncanrm said:
I am now second guessing whether I have plumbed up mine correctly.. ? (its a different layout to yours, I've possible got FM and FW wrong.. but the brakes do work, not road tested yet)

Any thoughts: Proportioning valve - https://photos.app.goo.gl/f5TXphPnQMp4oG1G6
Click to expand...

RW and RM I assume to mean Rear Wheel and Rear Master... as for which circuit in the master cylinder is front and which is rear, that varies between models. Probably best to ask if someone can post a picture.

I used to think that the circuit closest to the firewall on the MC was always the front circuit (as it is on my HIlux), but that does not hold. On my BJ60 system it's the other way round.

Additionally, I think it's best to use the correct disc/drum master cylinder for the vehicle - which I suppose you are doing, as I understand that all Australian 60s had discs on the front axle.

Nice work on the MC - did you make the brake lines yourself? I fancy having a go but I dislike the soft copper/cunifer lines. Did you get steel lines?

EO
 
Last edited:
duncanrm said:
I am now second guessing whether I have plumbed up mine correctly.. ? (its a different layout to yours, I've possible got FM and FW wrong.. but the brakes do work, not road tested yet)

Any thoughts: Proportioning valve - https://photos.app.goo.gl/f5TXphPnQMp4oG1G6
Click to expand...

You got me looking at my master cylinders. I am posting this just for (possibly only my own) interest.

The master cylinder you showed in your linked pictures looks very much like the original on my BJ60.

Here I have the original (end of life sadly) drum/drum brake master cylinder (47201-60330) which is 1 1/16" in diameter, and a (brand new genuine) disc/drum brake master cylinder (47201-60380) which is 7/8" in diameter.

A bigger master cylinder gives (for the same pedal force/travel) more fluid movement but at lower pressure. This would be suited to drum brakes I think, where wheel cylinders need to move further out to contact the shoes and then the shoes to contact the drums than pads need to move to touch a disc.

I would be interested to know what the diameter of your HJ60 master cylinder is (it should be cast into the master cylinder). Also, if your HJ47 is running the bigger bore drum cylinder, then it might benefit from getting the thinner disc/drum cylinder (and a proportioning and bypass valve!). Am I right in thinking siome fo the 47 series in Australia got 1 1/16" wheel cylinders (as opposed to the standard 1")?

EO
 
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Eurasiaoverland said:
I would be interested to know what the diameter of your HJ60 master cylinder is (it should be cast into the master cylinder). Also, if your HJ47 is running the bigger bore drum cylinder, then it might benefit from getting the thinner disc/drum cylinder (and a proportioning and bypass valve!). Am I right in thinking siome fo the 47 series in Australia got 1 1/16" wheel cylinders (as opposed to the standard 1")?

EO
Click to expand...
asd
Eurasiaoverland said:
RW and RM I assume to mean Rear Wheel and Rear Master... as for which circuit in the master cylinder is front and which is rear, that varies between models. Probably best to ask if someone can post a picture.

I used to think that the circuit closest to the firewall on the MC was always the front circuit (as it is on my HIlux), but that does not hold. On my BJ60 system it's the other way round.

Additionally, I think it's best to use the correct disc/drum master cylinder for the vehicle - which I suppose you are doing, as I understand that all Australian 60s had discs on the front axle.

Nice work on the MC - did you make the brake lines yourself? I fancy having a go but I dislike the soft copper/cunifer lines. Did you get steel lines?

EO
Click to expand...

I cant make out the markings on the master cylinder.. the casting is poor quality. Its an off the shelf after-market part from my local parts dealer.

The brakes lines are steel, my local brake shop did them. I dropped the master cylinder and valve in all bolted up with a diagram and they bent them up. Took a lot of torque on the nuts to seal them - not entirely sure if thats because they are steel lines or the flaring was suboptimal but they are sealed now. A road test may show otherwise once its under a lot of pressure and things heat up. I've remade the diff hard lines as well - for those I gave the brake place the length and I bent them to shape at home.

Yes, all Aussie 60s had a disc front as far as I'm aware.
 
sorry. It's not "my" domain. I found the link doing a google search. Maybe check the link in a couple of days to see if it is back up.

The link below is from a similar toyota document that seems to be available for free download. It doesn't seem to have the table of contents included so you will have to search through the document to find parts you are looking for.

kupdf.net

Brake Systems - Course 552 - Free Download PDF

Download Brake Systems - Course 552...
kupdf.net kupdf.net

I did find an assortment of the Toyota Brake system Technician handbook, used, on Amazon and Ebay. The course number (552, 553, etc.) seems to vary based on publication date.
 
Last edited:
2mbb said:
sorry. It's not "my" domain. I found the link doing a google search. Maybe check the link in a couple of days to see if it is back up.
Click to expand...

Whoops.. sorry, my bad. Thanks for the additional link!
 
2mbb said:
sorry. It's not "my" domain. I found the link doing a google search. Maybe check the link in a couple of days to see if it is back up.

The link below is from a similar toyota document that seems to be available for free download. It doesn't seem to have the table of contents included so you will have to search through the document to find parts you are looking for.

kupdf.net

Brake Systems - Course 552 - Free Download PDF

Download Brake Systems - Course 552...
kupdf.net kupdf.net

I did find an assortment of the Toyota Brake system Technician handbook, used, on Amazon and Ebay. The course number (552, 553, etc.) seems to vary based on publication date.
Click to expand...


You don't by luck know where a whole toyota/"toyota basics" course is? I'm quite enjoying reading this one on brakes.
 
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