strykersd

To start off the vehicle is a 1986 4runner with 310,000 miles. In the 3 years I've owned the truck, it's never stopped well. The truck finally starts braking about half way down the pedals travel.

Last week I did the V6 brake upgrade (calipers, rotors, booster and master cylinder) hoping it would cure the problem, but alas it did not. At first I thought there might be air in the system, but I bench bleed the master cylinder twice and bled the system numerous time (used a one man brake bleeder, a vacuum bleeder and the two person method) with no luck. There's no more air in the system, but the brakes are still weak.

I've checked the rear brake cylinders and they are adjusted right. So I've narrowed it down to either the LSPV (I've already modified it for my lift) or the brake lines. While checking the brake lines today it seems that they straighten out a bit when the brake is applied. Is that a tale tell sign that they're bad?

Thanks!

desertcamper67

Hey Patrick, it didn't stop well at Corall Canyon last summer either. Still haven't fixed it?

strykersd

Nope Tony, no luck yet. I bled the brakes earlier the week of Corral Canyon, so I was suprise how it launched down that rock wall. I was hoping the V6 upgrade would fix my problem, but that wasn't it. I was hoping someone has encountered the same problem before but if not I'll just run down to autozone tonight and replace the front brake lines (there only $12 a piece) and get a rear line from trail gear (for when I do 63" chevy springs).

Hijacking my own thread, Tony fix your diff yet?

DeathCougar

iTrader: (23)

A good upgrade would be to SS brake hoses. However, it sounds like you have a more serious problem. The LSPV could have failed, especially since you have just replaced all the front brakes.

strykersd

The rear will be a SS brake hose, but I don't plan on keeping the fronts for long. I'm still on the fence but I'll either go TC long travel or a SAS.

Ever see a LSPV fail? I'm wondering how I could tell. It doesn't leak at all. I figured it would either be permanently closed, not sending fluid to the rear at all, or permanently open. I'm thinking it might be the LSPV too, considering that while looking at the master cylinder the first half of pedal travel is all to the LSPV. Thanks guys!

limon32

Don't rely on bench bleeding the MC or on the truck MC bleeding, you must push fluid in from the resevoir ports with a syringe to get all air out of MC...

strykersd

So removing the resevoir and using a syringe will do it? How is that any better then just filling the resevoir? No bubbles are entering the MC when the resevoir is full...

hiltu

subscribed as i will be looking to upgrade my 85s 4runner brakes in the future

limon32

What I suspected and believe I proved on my truck is that after bench bleeding, you must put a line back on the MC right? How do you ensure that no air is between the new line and the bled MC? You can't, its impossible to ensure NO air enters the system when you replace the lines.

So the first time you push on the pedal, you push fluid from the MC into the new line right? Then when you let up, you suck fluid backin the MC and the air that was trapped in the line from reattachment. Once that air gets in, it gets trapped in the MC because of the upward angle the MC sits at.

I worked on mine several days with a buddy of mine from work, granted neither of us are mechanics but were both mechanically savvy. Nothing worked until one night I was ready to give up and my buddy says "seems like there is still air in there, almost like you have to push it out from the top". And I say, "check out this thing that came with the new MC".

The thing is a large syringe with a rubber stopper on the end that magically fits on the resevoir inlet on the MC. Now I thought it was for bench bleeding, but alas, when used to push fluid through the lines, in the same order you would bleed them, problem was solved in 10 minutes after HOURS of trying to bleed them traditionally.

Not saying i'm right, just saying what worked for me...

strykersd

I'll keep that in mind, thanks.

With the pedal only doing work on the second half of it's travel I'm thinking it's either the LSPV or the master cylinder. Possibly the LSPV is clogged, because it shouldn't feel like this if it was stuck open or closed. I'm planning on removing the LSPV tomorrow and bleeding the brakes to see if it could be that. If that doesn't do anything I'll look into pressurizing my reservoir and see if I can get any more air out.

bxlt

Subscribed! I'm having the same problem on my 86 truck. Replaced the rear brakes and have not had good braking since, originally just did the rears but just yesterday did a V6 upgrade on rotors, calipers MC and booster with slightly better results but still a real soft feel unless I pump up the brakes.

On a side note the amount of fluid I was getting out of the rears VS the front was drastically less.

cman1

iTrader: (1)

i had the same problem on my 86 pickup,it was that the LSPV wasnt bled enough,you wouldnt believe how much air it holds.i had no pedal at all,bled it twice,have 3/4 pedal now.

hiltu

revived a dead thread exactly 1 year since the last post.....

Ezrider_92356

are your rear drums properly adjusted?

bxlt

My bad in the sea of posts I was reading for all my different problems I saw the day but didn't look at the year...oh well worked out for me since I think I have the same problem that caman1 had

Yes they are good I really think it is a fluid and LSVP value problem at this point. I don't enjoy then but I have done my fair share of drum brakes

cman1 thanks I think that is my problem, I will try bleeding the LSVP and seeing if that works

I love yotatech the answer is here somewhere

strykersd

Good luck finding your problem! I never did find mine. I replaced the LSPV with a manually adjustable one, but it didn't seem to help. Oh well, I just sold my truck this past week so that's someone else's problem!

Cmayer

I'm having the same problem as well. I've searched quite a bit and haven't found a sure fire solution to the brake issue. Seems a lot of open ended threads .

One that I'm going to try and find is a syringe method of bleeding the master cylinder, but I'm not clear on what I'm looking for. If it bleeds from where the lines connect, or if it bleeds from the reservoir?

I've replaced a leaky wheel cylinder, both front calipers and pads, replaced both front soft lines, checked the entire system for leaks, bled with the traditional two person method, bled with a vacuum pump, and bled with a one way valve on a tube submerged in brake fluid. I've adjusted the rear brakes to the point that they just drag, but allow the wheel to spin freely. Nothing has corrected my issue.

When I first push the brake pedal it goes almost all the way to the floor. If I pump it with a quick push, let up, and push again the pedal feels great. I have to two pump every time I stop to get a good pedal feel.

At this point I'm tempted to just put a new master and replace the other wheel cylinder. However, I don't know if that will correct the pedal issue. So frustrating!

Capt. Red Beard

I too have the same prob. Also an 86. I replaced the rear shoes, and wheel cylinders. Bled the whole system thoroughly, sill need to pump to get some good breaking. I did notice that the discs on mine seemed much hotter then they should, like the rear was not engaging well, or at all.

I'll keep trying stuff, and post the results.

Co_94_PU

iTrader: (-1)

Pretty sure these are the "self adjusting" type drums.

Engage the the parking brake and put it in reverse. If it moves it'll self adjust when you stomp on the brake pedal, and you'll have to release the brake to get going again. best done on pavement of course.

BamaYota1

The brakes are self adjusting, but you still have to set them initially. There is a small slot on the dust cover right below the bleeder. With the tire off the ground, you've got to use a small screwdriver to stick in the slot and turn the adjuster wheel until you feel a very slight drag on the wheel. Once you feel drag, stop! Do the other side, then try your brakes. Parking brake should come out half as far as before, and pedal should feel firm.