Relyks

there were air in the brake lines so we decided to bleed the brakes now they go all the way to floor and dont grab also truck idle starts running rough when pumping brakes we by passed rear equalizer valve still no pressure...

xxxtreme22r

What did you do with the front pressure sensing line and exactly how did you bypass the LSPV?

Relyks

explain? were lost..

xxxtreme22r

Maybe it's best to rehook the LSPV then and bleed all the lines including the LSPV itself. Bleeding the LSPV last.

Relyks

is that a proportion valve in the rear by rear axle 2 steel lines coming into the back?

xxxtreme22r

There's more lines then 2 on the proportioning valve. It's 3 to be exact. 1 line is to sense the front caliper pressure, the other line is from the master cyl and the other runs to the rear brake drums via a soft line and tee. How did you bypass it? I can't help ya if I don't know how you bypassed it.

Relyks

we took the line with the most pressure and hooked it to the tee to the rear then we realized that the other line also has some fluid in it as well.

xxxtreme22r

both those lines that run from front to back are going to have pressure in them. One comes directly off a tee in the front passenger side fenderwell that runs to that caliper. The other runs from the master. If you just capped the one off that went to that caliper then it's going to have air in it as there is no way to bleed it. That's what line the bleeder on the LSPV bleeds.

There is a thread on here on how to properly bypass the LSPV. I bet that's what your issue is. And if you don't use a manual proportioning valve your rear brake line pressure is going to be way too high and the chance of you locking up the rear brakes is very likely.

Relyks

thank you very much this very helpful his step dad

ryanj4runner

Could not bleeding the lspv make the front calipers lock down on rotors after pumping brakes for a while? I cant figure out what is causing my 4runner to lock the front brakes i need serious help, thanks for any suggestions just bought this 4runner and spent two weeks replacing brake parts and still cant drive it more than a few miles

xxxtreme22r

Air in lines will *almost* never lock up brakes. Now what will is misadjusted rear brakes or low rear line pressure (somewhat unlikely) where they aren't catching and more pedal pressure is applied to get truck to stop. That will lock up front. Bleeding the LSPV only bleeds the front to rear sensing line not the pressure line. Maybe a bad master as well.

ryanj4runner

i just replaced over the past 3 weekends, the brake booster first, then the rubber hoses to front calipers and some hard lines i stripped, then new calipers and pads, and then new master cylinder. i bench bled master then 4 wheels but not the lsvp and the front calipers still lock down on the rotors after driving a few miles to test, last time i pulled into home and front brakes were smoking for a few seconds. i just bought a nice 1 man bleeder and am going to bleed everything again today and check rear brakes. if that doesnt fix it i really dont know what else to do thanks so much for any help

when i say "lock up" its not skidding to a stop the brakes fail to release after stopping several times and it revs way up just to start moving forward and then i stop driving it but if i open the bleeder valve real quick to release pressure then its fine again for short drive home

xxxtreme22r

Was this doing this before you put a new master on? I think you have a completely different issue then the OP does.

Relyks

mine ended up just being the master cylinder....

tazz76

Just like all new parts the master cylinder could possible be bad i had a 82 2wd that was having brake problems after 2 new master cylinders they worked fine. Also if there is any old rubber hose they can collapse not letting the pressure relief from the calipers stick ive seen this happens quite abit. Good luck hope you get it goin soon