denet

Anyone out there know where is the load sensing proportioning and by-pass valve (LSP & BV) on a 1996 Toyota 4Runner limited Edition 4WD.

I logon on the the http://techinfo.toyota.com, it is a Toyota dealer site and their manual shows that there is a load sensing proportioning and by-pass valve (LSP & BV) for 1996 Toyota 4Runner limited Edition 4WD.

I suppose to bleed it before I bleed four brakes.

Attached is a digram from that site.

I am trying to resolve a soft brake problme with my 4runner.

FattyCBR

If you crawl under your vehicle from the back and look at your rear axle the LSPV is attached to the frame and has an arm coming off it that attaches to the rear axle. The arm should be about 18"-24" long and is parallel to the axle. The arm should attach to the axle right around the middle of it.

denet

I have looked everwhere under the rear of my 4runner and I couldn't find anything you described.

Please help me look under my car at this link: http://mysite.verizon.net/res0zt44/


Thank you very much for your help.

FattyCBR

Well, I had a brain fart since I didn't fully read your question. Since you have a limited you don't have an LSPV, the ABS takes its place. So when you're bleeding your brakes go LR (left rear), RR, RF, LF.

Sorry about that.

denet

Do I need to bleed ABS? I bleed all four brakes and brake pedal still sinks to the floor when I step on it. I am pretty sure there is no leak hoses, wheel cylinder, and front brakes. Could ABS unit cause soft pedal? Master Cylinder is new.

My car stops OK at high speed(55mph+) but at low speed, the pedal is soft and sink to the floor.


Thanks,

FattyCBR

Was the system completely drained when you replaced the MC, if so I'd guess either the ABS booster or bench bleed the MC. Does the FSM have a section on brake bleeding after an MC or ABS replacement?

denet

I did do the bench bleeding. Can bad booster cause soft brake? What is the function of booster? Is there a test I can do to find out whether the booster is bad or not?

Is the brake line connect to booster also?

FSM does have a section on bleeding the brake and I followed.

Thanks,

MTL_4runner

A bad booster should make the pedal harder to stop.....it simply uses the engine's vacum to help apply pressure to the brakes during stopping. I assume you have gravity bled all 4 wheels but there must still be some air in the system if the pedal goes to the floor unless the new MC is bad.....was it from Toyota?

denet

When a Master Cylinder is bad, does it leak fluid out or it doest? The new Master Cylinder I install is purchased from a local auto dealer not from Toyota.

I will double test the Master Cylinder though.

I am 100% sure the brake systems is not leaking becasue I used Motive power bleeder to test it. It creats a vaccum and push down the brake fluid from brake reservior and I never find any wet spot around all four brakes.

My booster work fine, my brake is very easy to depress down.

Thanks,

TechWrench

It is possible for the internal seals on the master cylinder to leak and bypass fluid without any sign of an external leak. This could cause symptoms you describe. But air in the lines which has not been bled out could also do that. Also, if you just installed new pads or shoes, and the caliper pistons and or wheel cylinder pistons were recessed all the way in to install the new parts, you may not have gotten them back out to their normal positions.

User 051420

This is likely a shot in the dark but....I've been having a really really soft pedal and a huge nose dive whenever I stop. The local shop that did my rear wheel cylinders/drums/shoes said it was normal because of my bigger tires. Possible, but not as severe!

I JUST found this thread https://www.yotatech.com/forums/f2/adjusting-rear-brakes-6137/ and went and and tried it...woo hoo! 8 "clicks" up and my pedal is normal, and my truck stops!