smilen724

i've been having the same problem in my 86 toyota pick up. i have replaced EVERYTHING in the brake system and have bled them several times. it still has bubbles coming out of the right rear. would the LSPV have anything to do with this? does anyone know how the lspv actually works? the order i've bled them is LR, RR, RF, LF, LSPV. thanks

Ryall

I've got a problem that's very similar to this. It popped up very recently - my truck was parked one night with the brakes working fine and when I got into it the next day the brakes went right to the floor.

When I checked under the hood there's a hissing noise coming from the master whenever I pump the brakes. I'm hoping that the master isn't gone since they're hard to come by around here...

Also - I've got an 89 Pickup

Figure4

@Smilen724 My LSPV was bad also along with alot of other people on here, I ordered a manual proportioning valve from summit. I spliced that in right after the MC, and ran a new line all the way to the T above the rear axle which bypasses the LSPV all together. A new line is not necessary but the section next to the gas tank is prone to failure on these trucks, mine was blown.
There are a few write ups on how to install the valve here just search around and you will find it.

NARFALICIOUS

Okay people I will bump here because no one likes new threads.

Having trouble.

88 4WD Pickup, 4 cylinder, manual everything.
I recently replaced rear shoes/springs/wheel cylinders. Also adjusted the brakes out and finally have a semi-decent parking brake.
By this I mean the left side grabs right away, the right is kinda ehhh. I'm assuming because the cable on the left goes from the center all the way to the drum, whereas the right is attached. I tried adjusting it at the attach point. Not sure where else to adjust them. Either way, it holds on inclines on its own now; before it didn't.

Also, bled the brakes several times, ran through 1-1.5 32oz bottles of brake fluid. Used the two person method, 3 pumps, then hold. Also threw in a one slow pump in there every now and then. Bled a few times RR, LR, RF, LF and had trouble getting a firm pedal. But then after searching I found it best to bleed LR RR RF LF LSPV. After bleeding the proper way once, I think maybe twice and air definitely came out and got a bunch of it out, clean smooth fluid started coming out consistently. And I'd got it to where it's a firm pedal engine off, and a firm pedal engine running. Only drove it around the neighborhood (5-12mph), stops good. Next morning I drove to work, which is a short 5 mile trip but has speeds up to 40-45mph, stops good when I'm stopping slowly, but if I pressed all the way down, I'd get the bottom of the floor and there was no "grab"; like brake force builds up to a certain point, but at full pedal press no more force builds up...if you understand what I'm saying. Basically I would could stop fine if I gave an extra 2-3 seconds of braking space, but in a panic stop, that panic stop "grab" isn't there.
So I brought it home safely, bled it that night, and also the next morning (which is today) and it still feels the same. As if I've reached the end of what I can improve by bleeding.

Never ran the master dry.

Not sure if at this point I should try to continue bleeding it and run through another bottle, or gravity bleeding it, or bench bleeding the master, or inspect for internal leaking master into booster. I'm not going to throw a master cylinder at it unless I know in fair certainty that it needs it, since I'll be buying new, not reman (after reading various posts about bum masters)

Ok thanks for reading.

osv

you can bleed the master when it's on the truck... first wrap a rag around the connections... do the same pump three times, then slightly crack the nut to one of the lines as pressure is held on the pedal... I like to close the nut while the pedal is slowly sinking to the floor, just before it stops it's travel.

this works great in your situation, but on a new master it can be difficult to get the first pressure buildup on the pumps... but I have been able to make it work well on two brand new masters... I was even able to do it by myself, using a 2x4 to hold the pressure on the third pump :-/

at this point i'd be wondering about the vacuum booster as well.

millball

I read a post on page 1 of this thread reccomending that multiple bleeders be opened when gravity bleeding. This is not a good plan.
There should never be more than 1 line open at a time.
Many times I have seen one bleeder drain and pull air into another line that was open at the same time.
It is usually best to bleed the longest run first (right rear) and the shortest run last (left front).
If a brake system is in good shape, gravity bleeding usually works well.
When I get a new to me car or truck, one of the first things I do is suck the fluid out of the master cyl, refill with clean juice, and then gravity bleed every corner until only clean new fluid runs out.
Brake fluid absorbs water and should be changed and the system flushed anytime the fluid gets discolored at all.