adamthedroog

I've been having this problem forever and I'm losing my mind. My brakes will go to the floor when I'm driving. I've already replaced the master cylinder, bled it, bleed all of the lines with the car on and off, bleed the power steering, and adjusted the LSP. I think it may have something to do with the ABS (By the way, I've got rear-wheel ABS) like it's bypassing it somehow but I'm not sure. Can anyone please help?

93toyrunner2

Year, make, model?
Any recent brake work?
Brakes worn out?
Rear shoes adjusted good?
Any leaks in lines?
Did you follow the FSM bleeding order?
Have you gone along each line, and bleed it at each joint where the line has fittings?
Have you bleed the LSP line from the front brakes connection?
When you pump the pedal, does it get harder?

adamthedroog

Year, make, model? - 1990 Toyota 4runner 3VZE
Any recent brake work? - No
Brakes worn out? - No
Rear shoes adjusted good? - Yes
Any leaks in lines? - No
Did you follow the FSM bleeding order? - Yes
Have you gone along each line, and bleed it at each joint where the line has fittings? - Yes
Have you bleed the LSP line from the front brakes connection? - Where is that? I've only bleed the LSP itself.

scope103

Does the brake pedal drop without resistance all the time (as in, you have no brakes ever)? Or does the pedal slowly sink to the floor when you're sitting at a light?

The latter is almost always a leaking master cylinder, or possibly a leaking line (but you'd know that; you'd be out of brake fluid in only a few minutes).

The usual symptom of air in the brake line is "sponginess," or the pedal goes too low all the time, and you have much less braking effect.

adamthedroog

When I'm slowing down the pedal will sink to the floor and the brakes will kind of work. When I'm sitting at a light I can feel them sink a little bit. Nothing is leaking because I've checked everything and I never lose fluid. My master cylinder is brand new.

xxxtreme22r

Does your ebrake work? Serious question BTW.

adamthedroog

Ebrake works fine.

adamthedroog

When I'm sitting with my truck on there's a lot of travel before I feel any resistance. When I do the pedal is really spongy and I can easily push it not to floor but I feel it hitting something metallic. If I just apply some pressure to them they will slowly sink down.

snobdds

Your getting air in somewhere... Have you checked your rear wheel cylinders? How far down the system can you get fluid?

Also, your ABS system gets its constant pressure from the power steering pump (system), giving it that pressure when called upon. You will need to check that entire system for leaks and such...

Update:

Here is the link for the relationship bewteen the two systems. I know it's for a 22RE, but I bet the two systems are similar.

http://www.ncttora.com/fsm/1990-1995...e/absactua.pdf

adamthedroog

I know all about that. There's no leaks anywhere. Someone said there's somewhere in the front to bleed the LSP which I've never done so I'll look into it tomorrow.

93toyrunner2

See the following link for more information about bleeding the brakes and other issues.
https://www.yotatech.com/forums/f120...eeding-244093/
Maybe xxxtreme22r can jump in about the LSPV line from the front. I do not have this system, so I can not pinpoint where it is.

snobdds

Good, then what's the problem again...?

Northern Sun

i think i got answer for U ..
i've been playing with 5 lspv units; 2 boosters and 4 or 5 master cylinders and i cant get them brakes to work properly again ../,, ; i did calipers job b4, 4 shelfs and afterall 2-ready units; old calipers were 3:1 & 4:2 seized; new/old came out 4:4 both ok, but i think they would fail under pressureized brake system test, there is no other explanation, i think im getting myself NEW rebuild calipers ..