need a toyota guru

[binderbart]

93 toyota hi-lux, ext. cab, 2wd, 22re. brakes not working right, he put 2 master cylinders on in the last year. no rear brakes. brought it to me. new master cylinder, bench bleed, rod on booster is adjusted right( will push fluid thru both ports when installed) cant get brakes. this system is different to most other brand cars. why do they tie the front and rear lines together with T fittings?

 

[85+92]

getting fluid TO / OUT the rear lines?

wheel cylinders leaking?

 

[binderbart]

nothing leaking anywhere. once we got the master bench bleed, I went to the farthest rear line. first bleed was great , no fluid after that. went up to the LDPV, one good shot out of that, and then nothin. the two lines running to the rear were pretty rusted at the LDPV so it was late and I quit there. about 4 different guys came by and all are confused. why do they tie front and rear lines together?

 

[raevenzero]

Make sure rears are adjusted properly and load sensing proportioning valve. Bleed the brakes at every connection.

Use the jar and fluid trick. Make sure calipers aren't on upside down, cause air to get trapped.

If all else fails, use a compressor to push fluid through the lines.

 

[raevenzero]

Try putting a plug in master cylinder rear port and see if you can get fronts to work and vis versa. That will at least isolate the problem.

 

[binderbart]

rear brakes are new and adjusted just right. no leaks anywhere. Does anyone have a lay out of the complete brake system and what each elbow and T fitting does? Toyota has a wierd system . front and rear lines tie in together. Never seen anything like it. I dont want to just start changing parts on this till we find it. got to be a way to bleed it out.

 

[Chop Shop]

Just get rid of that gay proportioner. I have removed tons of those junkers.

Unhook it, then find the tee on the passenger frame rail in the front wheel well. That tee is where it diverts pressure to the front right wheel.
Unhook the line going to the rear off of that tee and put a plug in the tee or just get rid of the tee all together and run the front line right down to the hose tab for the front right brake.
Then take the unhooked line that goes to the rear and blow thru it to see which line it is in the rear. After you determine which line is the unhooked one bend it out of the way and rehook the one that didnt blow back to the rear brake hose.

Then enjoy bleeding you normal brakes.

 

[KLF]

I believe you either have a faulty LSPV, or some sort of a blockage in one of the lines.

The F&R circuits are tied together by the pass side front wheel, as this is the excess pressure from the rear circuit that the LSPV is sending to the front circuit.

I would start by disconnecting the lines from the LSPV, maybe up front as well, blow air thru them and ensure they are clear, also inspect for any kinks or crushed lines along the frame rail, which will be tough by the gas tank. Hopefully everything is not rusted solid and you can get the fittings off, sounds like you know to use a flare wrench.

I suppose you could ditch the LSPV like CS says, just abandon the return line and plug the T at the front. A new LSPV is very expensive. I would probably opt to go with a manual prop valve, either under the hood or in the back. Wilwood makes a good one, Summit sells a kit that includes the adapters to convert to metric thread.

 

[toy4xfun]

i would only eliminate the LSPV if it is my truck if it belongs to some one else i would recommend they replace it! just my .02

 

[corax]

Here's the Field Service Manual for the Brake System

The F&R circuits are tied together by the pass side front wheel, as this is the excess pressure from the rear circuit that the LSPV is sending to the front circuit.

nope, but that's a popular misconception. How does the LSPV move fluid from the rear brakes to the front, to an area with higher pressure, without a mechanical pump? the line going to the front brakes is only used for "pressure sensing" in case of front brake failure - here's some reading on how proportioning valves work, scroll down to pg 13


Here's my write-up for getting rid of the LSPV

 

[cruiser88]

thats freaking awesome.

Here's the Field Service Manual for the Brake System



nope, but that's a popular misconception. How does the LSPV move fluid from the rear brakes to the front, to an area with higher pressure, without a mechanical pump? the line going to the front brakes is only used for "pressure sensing" in case of front brake failure - here's some reading on how proportioning valves work, scroll down to pg 13


Here's my write-up for getting rid of the LSPV

 

[binderbart]

Just get rid of that gay proportioner. I have removed tons of those junkers.

Unhook it, then find the tee on the passenger frame rail in the front wheel well. That tee is where it diverts pressure to the front right wheel.
Unhook the line going to the rear off of that tee and put a plug in the tee or just get rid of the tee all together and run the front line right down to the hose tab for the front right brake.
Then take the unhooked line that goes to the rear and blow thru it to see which line it is in the rear. After you determine which line is the unhooked one bend it out of the way and rehook the one that didnt blow back to the rear brake hose.

Then enjoy bleeding you normal brakes.

If I were to do this wouldn't it cause the rear brakes to lock up every time the brake pedal was applied? that prop. valve is what regulates the proper pressure between the front and rear....correct?

 

[binderbart]

Here's the Field Service Manual for the Brake System



nope, but that's a popular misconception. How does the LSPV move fluid from the rear brakes to the front, to an area with higher pressure, without a mechanical pump? the line going to the front brakes is only used for "pressure sensing" in case of front brake failure - here's some reading on how proportioning valves work, scroll down to pg 13


Here's my write-up for getting rid of the LSPV

Looked at your right up, and I like it. simple . where does a guy get the valve you used and how much are they? I'm sure you could even get plugs from a part store if you looked hard enough.

 

[toy4xfun]

i would think it might on wet or slippery roads, but not sure if it would on dry pavement, but that is why some one said to put an aftermarket adjustable on there, but then the owner has to play with it to get it set when the truck is unloaded and then again if he loads it. (i would think)

that is why i said i would not take it off if it was not my truck.

also take a peak at corax's link where he removed his, i have met him and keith has some great knowledge, to bad he left the area before i could pic his brain some more.

 

[toy4xfun]

well you beat me to it.

 

[KLF]

here's some reading on how proportioning valves work, scroll down to pg 13

<printed for future reading>

But I already read thru a bunch of training manuals when my son was enrolled in a T-TEN program a few years ago. Maybe I over-simplified my response. Still, this will be interesting reading, should go in the FAQ.

Here's my write-up for getting rid of the LSPV

Your modification is exactly what I have planned. I already have that exact Wilwood valve & adapters, plus I have a couple of residual valves for the RDB setup, not sure if I'll need them or not. Nice job mounting!

 

[Chop Shop]

If I were to do this wouldn't it cause the rear brakes to lock up every time the brake pedal was applied? that prop. valve is what regulates the proper pressure between the front and rear....correct?

meh.

Toyota rear brakes suck so bad I dont think they will lock up even if working perfect. But thats just me and my .02

 

[corax]

Looked at your right up, and I like it. simple . where does a guy get the valve you used and how much are they? I'm sure you could even get plugs from a part store if you looked hard enough.

Speedway Motors has them for $33 here. Summit Racing or Jegs also carries them and you can probably find them in any respectable hotrod or racing equipment store. Just look for the knob style like I have in the link - they're all the same and brand name doesn't matter much with a simple part like this.

You might be able to get a plug, but I don't know where. I think the plug threads are 10mm - 1.0. Or you can forget about messing with the "T" and try to find a 90 degree brake line adapter from the same location on another toyota truck, like the one on the left in the pic below

Another option, if you can flare a brake line:
- cut the original Toyota ends off at the "T"
- slide new 3/16" SAE sized nuts over the bare ends
- flare the line and use a male-male adapter like I had to do in the pic below (vertical part next to the brake booster) to adapt the proportioning valve to the stock lines (but do this at the "T" in the pass. wheel well)

 

[Bogo]

meh.

Toyota rear brakes suck so bad I dont think they will lock up even if working perfect. But thats just me and my .02

I got some debris into the adjusting arm on the one on my '94 and it would lock them up. Removed the debris and the problem went away. On my '89 if I push on the brakes to fast it will lock them up before the tail end lift has reduced the pressure to the rear. I've been making some adjustments to it, but it isn't quite right yet.

 

[WristPin]

when isolating problems you can clamp off the brake HOSES with specialized clamps or vice grips. dont try it on aftermarket steel bradied lines.

are the rear shoes even adjusted properly??