Does your system have a proportioning valve inline? Could have gone bad, or need adjusting.
Issue with front brakes, master cylinder issue?
- Thread starter Rustic76
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[QUOTE="Rustic76, post: 10625002, member: 61089"]I also pulled the valves and this is what they look like, both identical. If I remember correctly, I replaced a 40 series master cylinder with a centric/auto store variety on a '76 and had to swap both of these valves with the old Aisin ones because it wouldn't work right. Maybe I'm on to something?[/QUOTE]
Looks like you maybe on to something here!...Note the different part numbers for the valves in the red box.
Strange that there's no check valves for the rear drums!
Looks like you maybe on to something here!...Note the different part numbers for the valves in the red box.
Strange that there's no check valves for the rear drums!
- Thread starter
- #23
Does that literature indicate which is for disc/drum combo?
The OEM definitely has more to it than this aftermarket master on here.
The OEM definitely has more to it than this aftermarket master on here.
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- Thread starter
- #24
I followed the brake lines back and found that it has a LSPV- load sensing proportion of valve. I pulled out the FSM and this thing and it's workings seem complicated, beyond my feeble skills. Wonder if this is playing a factor in my problems. It has a bleeder nipple so I guess I'll start there and see if any air is trapped.
- Thread starter
- #25
Well I think I found at least part of my problem. While trying to bleed the LSPV, I put a little pressure on the rubber boot at the bottom and brake fluid started pouring out. I pulled the arm off and removed the boot and the valve is leaking from the bottom. Looks like next up is either trying to bypass the LSPV or finding a replacement.
I just had the same problem on an 87 mini truck, could not find a replacement, so I pulled it apart and replaced the o rings, been ok since. But this has to do with your rear brakes, not your front brake issue? The check valves on the master definately limit presure, so you might have an issue there.
- Thread starter
- #27
Why in the world would the brake line supplying the front brakes T off at the frame and go all the way down the frame to the LSPV? It parrellels the brake line for the rear brakes which also goes to the LSVP. When I saw this I figured it must involve the front brakes somehow?
Bleed the master at the master. If you do not have good fluid flow there, you have found your problem. If you have good fluid flow then move down the line until you reach the calipers. Don't skip any hose connections on the way. When these hoses come apart inside they are impossible to see and the only way to know is to check the flow/pressure from each side of them. Frozen calipers will generally give you a rock solid pedal.
Its a presure return line, very goofy setup
47210t in the schematic can sometimes not be in the correct spot on the piston limiting flow. I bypassed the lspv on my fj62 by putting a bleeder valve where the lines go back and installing an adjustable prop valve. That way, front is front and rear is rear. If that were mine I would get all new hoses and new master and upgraded calipers on the front. I have the pn#S handy at the office. I would bypass the little hard line on the front backing plated, install soft lines directly to the caliper. New drop hoses and new master. And get v6 front calipers. It'll be about $300 or more to do it right but you will know your system. I have a pn for a metric adjusting prop valve as well. Way better to stop than to go.
And I have seen front lines swell as well almost died on a test drive after a disk conversion. I'll pm u part #S tomorrow if u would like to upgrade the whole shebang. But in the meantime try that little bolt in the side of the master, have someone step on brakes with it out and front bleeder open and then reinstall see if that helps
Do you know if the front discs are factory fitted or convert from a 60 series?
If its a conversion the correct parts need to be used to function properly , note the different master cylinder and rear wheel cylinder sizes between drum/drum and disc/drum.
Top page is Disc/drum
If its a conversion the correct parts need to be used to function properly , note the different master cylinder and rear wheel cylinder sizes between drum/drum and disc/drum.
Top page is Disc/drum
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- Thread starter
- #33
@tornadoalleycruiser, I'll take those part numbers when you got them handy, appreciate it. After poking around the LSPV is leaking pretty bad from the bottom. I hadn't noticed it sooner because the boot was holding it all the fluid. I think I'll try bypassing like you said.
@nogo they are factory fitted discs.
@nogo they are factory fitted discs.
- Thread starter
- #34
So the non-USA OEM brake master for my application is discontinued. After searching for applicable interchangeable parts I can't find one listed. It looks just like the 60/62 master and in searching mud but looks to have a different bore diameter, some have suggested it works.
Does anyone know which one will work?
Does anyone know which one will work?
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This issue sounds like the master has a bad seal in the front circuit--initial pedal application moves the calipers, then they relax. The master is bypassing fluid past the seals back into the supply--ergo-no pressure( I would guess, tho' that something is also going on with the rears also--the pedal should go flat for the leaking front circuit, but the rears should stop pedal movement ~ halfway down if they are holding ok)
- Thread starter
- #36
The pedal is very light to near bottom, then the rear brakes grab at the bottom of the pedal.
Search for PBR JB 1526 or equivalent....There's a few on ebay AU.
- Thread starter
- #39
There is a handful of master cylinders from this era that look nearly identical but all have different part numbers for different applications. None that I have found here in the states list as interchangeable with the original discontinued part#47201-60200.
These calipers have bigger pistons and will take a bit more fluid. I normally run a 1" master and 4wheel disks. and they will require a slight trim of your backing plates, Very simple to do. if you don't want to upgrade calipers as large then go with 1985 FJ60 calipers or something similar. Slightly smaller pistons and probably will not need the larger master to feel correct. The smaller calipers take different pads as well.
Hoses will stay the same regardless if you bypass the backing plate hard line. Reason for this if you ever do any service you can remove the caliper without breaking the fluid system. I normally run backing plate deletes or cut the backing plate off and use the remains as a "spacer" or basically make my own delete plates.
Calipers I normally upgrade to, 89 4runner, need pads and pins as well.
I get calipers local and use my old cores to avoid shipping cores back. These pn's were Oriley auto or Rock Auto.
Front Caliper BrakeBest Brake Caliper 19-1240
Front Caliper BrakeBest Brake Caliper 19-1241
Front Hose caliper to axle RAYBESTOS BH38881 (bypass the old hose and hard line and go directly from axle to caliper)
Hose Frame to axle (extended rubber drop hoses) RAYBESTOS BH38009
Prop Valve
Summit racing PN Wilwood 260-12627 $40
To bypass the LSPV you will probably need to run a longer hard line to go to the rear drop hose when bypassing the LSPV circuit. You will see this if you trace the system. It "loops" back to the front when the truck is at an extreme angle nose down. the junction block up front has too many fittings and returns rear brake pressure to the front system or something like that.. I seem to recall using a brake bleeder to fill the extra hole or used an FJ40 junction block. It's been a while. then made a new hard line that extended to the rear drop hose and bypassed the whole shebang. Also shaved about a pound of parts off the truck by removing. That has to be good for mpg ?
I keep a spool of brake line and have a super cool double flare tool so for me it's a simple job.
https://www.amazon.com/dp/B01HOXH242?tag=ihco-20
not the exact one i have but they put different names on the same tool.. Eastwood rebadges the tool and charges more..
So.. FWIW, I would bypass the LSPV, install a rear adjustable prop valve, simple to mount under the master inline with the now ONLY REAR brake circuit. and install new calipers and hoses and probably a master.. Then you know everything is new, updated, safe. You will need to dial in the rear brakes after all this.. Normally involves gravel lot, a spotter and lots of test hits with the brakes.
I would also quit worrying about a "foreign market" master cylinder. I just cannot see that toyota would use a country specific brake master..
I'd guess with the purchase of the tool if needed, your looking at about $500.. without the tool probably $300 or so to be safely stopping again.
But.. It might have been as simple as the current master you have being put together incorrectly and the piston is not in the correct location. Don't know if you tried the little bolt on the side adjustment or not.
Good luck! Let us know how it goes.
Hoses will stay the same regardless if you bypass the backing plate hard line. Reason for this if you ever do any service you can remove the caliper without breaking the fluid system. I normally run backing plate deletes or cut the backing plate off and use the remains as a "spacer" or basically make my own delete plates.
Calipers I normally upgrade to, 89 4runner, need pads and pins as well.
I get calipers local and use my old cores to avoid shipping cores back. These pn's were Oriley auto or Rock Auto.
Front Caliper BrakeBest Brake Caliper 19-1240
Front Caliper BrakeBest Brake Caliper 19-1241
Front Hose caliper to axle RAYBESTOS BH38881 (bypass the old hose and hard line and go directly from axle to caliper)
Hose Frame to axle (extended rubber drop hoses) RAYBESTOS BH38009
Prop Valve
Summit racing PN Wilwood 260-12627 $40
To bypass the LSPV you will probably need to run a longer hard line to go to the rear drop hose when bypassing the LSPV circuit. You will see this if you trace the system. It "loops" back to the front when the truck is at an extreme angle nose down. the junction block up front has too many fittings and returns rear brake pressure to the front system or something like that.. I seem to recall using a brake bleeder to fill the extra hole or used an FJ40 junction block. It's been a while. then made a new hard line that extended to the rear drop hose and bypassed the whole shebang. Also shaved about a pound of parts off the truck by removing. That has to be good for mpg ?
I keep a spool of brake line and have a super cool double flare tool so for me it's a simple job.
https://www.amazon.com/dp/B01HOXH242?tag=ihco-20
not the exact one i have but they put different names on the same tool.. Eastwood rebadges the tool and charges more..
So.. FWIW, I would bypass the LSPV, install a rear adjustable prop valve, simple to mount under the master inline with the now ONLY REAR brake circuit. and install new calipers and hoses and probably a master.. Then you know everything is new, updated, safe. You will need to dial in the rear brakes after all this.. Normally involves gravel lot, a spotter and lots of test hits with the brakes.
I would also quit worrying about a "foreign market" master cylinder. I just cannot see that toyota would use a country specific brake master..
I'd guess with the purchase of the tool if needed, your looking at about $500.. without the tool probably $300 or so to be safely stopping again.
But.. It might have been as simple as the current master you have being put together incorrectly and the piston is not in the correct location. Don't know if you tried the little bolt on the side adjustment or not.
Good luck! Let us know how it goes.