deathrunner

Ok, so my pedal got really spongy and would drop when at stop lights. I figured something was wrong and decided to replace the Master Cylinder and Brake Booster.

So, I got everything on and I believe I got the MC bled correctly. I was able to suck fluid to the front tires and get the aire out. We have one of those handheld vacuum pumps to bleed brakes.

When it comes to the rear, we aren't getting any pressure. Not sure if it is a clog or leak or what. Is it possibloe that the rear portion of the master cylinder is broken?

Coul the LSPV be the culprit? It is disconnected as my suspension travels to far for it. It is old and looks it. The rubber boot is torn real bad. Would it be worth replacing/rebuilding?

Any Suggestions would be great. I'm all ears.

jason191918

Are you losing any fluid?

Justinvd

did you bench bleed your new MC?

Elvota

I'd agree with the above.. make sure you BB the MC.

Also, I have had good luck using a vacuum pump to draw brake fluid through the lines. That will also tell you if you have a clog or bad LSPV if even the vacuum can not draw fluid.



Also, "speedbleeders" work really well at the calipers for any bleeding efforts:

Summit Racing
RUS-639560 (Qty 1pr): 10mm x 1.0 Thread, 35mm length (Toyota)

Justinvd

Sorry to thread jack but whats the LSPV? my technical term knowledge is sad haha.

RobD

Load Sensing Proportioning Valve

and ye shall receive.

http://toyota.off-road.com/toyota/ar....jsp?id=186295

http://www.4x4spot.com/proportioning.htm

just a 22re

hey deathrunner long time no see buddy anyways what you should try first is check and see if you even get pressur back at the lspv have a friend or a kid pump your brakes and just try to crack open the brake line before the lspv and see if it leaks then do the same but after the lspv then you will know where abouts the problem is and by the way we should have gone wheeling when i was in san deago by the way but if i was there still i would come over and help you wait no way i saw you that day you were at the mini mall thingy there i was at the chinisse eatery i though i saw your truck maybe all wells there was like 3 younger kids that got in it lol

just a 22re

ok after looking at you truck again no it was'nt your rig my bad but yeah try that out and see how it goes

deathrunner

Well, we did bleed the mc on the bench, althoughnot sure how long that lasted. I think we sucked air back into it while attempting to bleed them.

We have a vacuum pump as shown above. We were able to get light pressure at the lspv, nothing at the rear brakes.

How do I determine if I have a leak or a clog? I wasn't losing fluid before.

If there is a clog, what is the best way to rectify it? I am thinking about hooking up my air compressor to the brake lines and blowing through them if possible.

Thanks for any and all help.

dirtoyboy

are you bleeding in the correct order? are you bleeding the LPSV itself?

deathrunner

No, I have not done it in that order. I searched on here and the order i got was RR, LR, RF, LF. There was no mention of the LSPV, so we just assumed it cam before the RR.

I will try your suggested method. Makes sense with the diagram. Much Thanks.

CyMoN

when I bleed breaks I have one of those hand pumps and it works ok if I have a helper what I do is have them pump the pedal about 4 or 5 times I have the vac pump hooked up I open the line they tell me when the pump has hit the wood block then I close the line back up and repeat until either the fluid runs clear or no bubbles usually it takes filling the little reservoir on the hand pump one and a half times.

I also have found it a good idea if you don't care about spilling break fluid is to open the Tee on the back axle have some one pump it then block off the line with your finger so it dose not suck air back in the line when they let loose of the pedal usually 8 pumps dose the trick by doing this it dose not allow any sediment in the lines to collect in the rear brake cylinders and it can blow out blockage better if you have some.

spdjnky

try taking the bleeder screw out of both rear calipers and let if free bleed. you can actually do it on all four to make sure there is no air in the lines at all. This is how I have done it before when all my friends are MIA! Take the top off the MC and watch the fluid level. I have had bleeder screws "clogged" not causing any fluid come out until I did the above procedure.

*edit* this may take a while but it works!

deathrunner

spdjnky,

So, just open all the bleeder valves and let gravity pull the fluid through? Am I hearing that right? I'll give it a shot.

nv4runner

gravity bleeding will work, but it takes forever. with your LSPV disconnected you will get hardly any pressure to the rear brakes, so to bleed them you might want to at least tie it down to simulate a load so you can have full pressure and flow to the rear wheel cylinders. Make sure you keep the MC full of new brake fluid! Otherwise you have to rebleed the entire system starting with the master cylinder and then going to the furthest slave cylinder from the master and working your way to the closest (easy way to remember how to bleed with a split brake system). If you use a vacuum bleeder you should take the bleeder screws out and wrap a little teflon tape around the threads and put a small blob of grease on the nipple so no air will be able to leak around those areas and give you more bubbles than you really have in your system. Use the grease if you use a bleeder screw fitting. Probably don't need it if you just push a hose over the nipple. The teflon will also keep the bleeder from corroding and binding up so you'll always be able to break it loose without actually breaking it.

dirtoyboy

With a name like "Deathrunner" what do you need brakes for?









fix it yet?

deathrunner

Awesome thanks for the info. It's going to be a slow repair. I'm keeping pretty busy these days. I just wanted to run through all the options before I even touch it, anyway.

What's with this block of wood under the pedal thing? Anyone I mention it to says they've never heard of it before. The most common question I got was "What size is the block? 1X2 2x4 4x4??????"

Is it to protect from over extending the master cylinder? Because when we bench bled it, we pushed the cylinder all the way in. Sometimes it would kind of get stuck halfway when coming back out. Does that sound normal?