blake.nemitz

ive had a similar problem after a brake overhaul. it ended up being the rear shoues were pulled in too far and since i had a broken cable for the e brake i couldn't adjust them like they should be. they are adjusted by the ebrake not normal operation. my .02 glad you got it fixed. nothing is more unnerving than brakes that dont work or you have to pump the pedal once to stop

Nuyota

Well, they're not totally fixed. I was doing the procedure to check booster function and airtightness and they checked out. Pedal still felt like it would go in too far before engaging. Then went to drive down the street and had no brakes, they just sunk to the floor. Pumped it a bunch and brakes came back. Still stumped. If idling and pumping brakes truck starts to stall out so pretty sure I have vac leaks somewhere round the engine. If I pump brakes when I'm also on gas the brake pedal gets much firmer. E brake works but i have to pull it all the way out on a slope. Also tried yanking it a bunch of times to set them in. There is no fluid loss. I'm gonna check out some stuff myself but it seems like it's hydraulic related. There must be a huge air bubble or something. The only way the brakes would sink to the floor is if there's no pressure so i dunno.

ksti

There's got to be air somewhere still.
Were the brake hoses replaced?
If not one could be collapsing (internal wear) causing erratic pedal.

Nuyota

Everything was replaced. BMC, booster, front pads and rotors, rear shoes, rebuild kit, cylinders, all 3 hoses. E brake works and no loss of fluid. I'm guessing air too since everything was replaced everything was dry and that's alot of air to get out. Got in the truck last night and before starting brakes sunk to the floor so had to pump a bunch then they worked ok but low engagement point. They're acting really inconsistent.

ksti

I didn't see that front calipers were replaced.
I have read that sometimes old bleeder screws don't seal all the way, letting in air but not leaking fluid.

Blue1991

I read this whole thread from start to finish. Whether it was done or not, I did not see you account for having bled the load sensing proportioning bypass valve. It was mentioned by one or two people, but, haven't seen you confirm it. RR, LR, RF, LF, then LSP, correct? Assuming the master cylinder was bled right to start.

Blue1991

I hate having to hassle a shop owner or manager- so frustrating. Hope you get this all straightened out.

Nuyota

I recall that proportioning valve being mentioned before, but I thought it was referring to adjustment not bleeding it. I will be using the fsm to manually bleed the system myself to check everything so I will follow that sequence. To confirm bmc was bled proper should I do that first or last? The way I read to do the bmc is remove both hard lines and use middle hole and finger to bleed is that correct?

ksti

IMHO I would remove the master cylinder completely as you don't want brake fluid all over your engine bay.
Remove it put in a vise and bleed it.
You can also get a MC bleed kit at your local AP Store to contain fluid back into MC as you bleed it.
Saves on brake fluid and a big mess. Just don't let the reservoir get empty.

Blue1991

Yup, Nuyota, you got it...BMC first. Besides it being messy to do it while the BMC is in place, it's near impossible without a helper...I often don't have a helper. Either way, that is the first thing to bleed, unless you're sure it doesn't need it (but it seems legitimately questionable in this case.)

ksti is right, bench-bleeding it (removed from the truck, in a vise) is the way to go.

BMC, then RR, LR, RF, LF, then LSPV.

Keep the reservoir topped, and don't give air a chance to suck back in. And, since it does no good to assume, only use a brake line wrench on the line connections and bleeder screws- for sure.

Hope you have a clear understanding with the shop you had work on it. If nothing else, I guess that is putting you in the learner seat! That's good, yeah?

Blue1991

To be clear, "BMC, then RR, LR, RF, LF, then LSPV", that is the bleed sequence.

Adjusting the LSP-BV (sorry I keep using different letters for it [the load sensing proportioning and bypass valve]) requires some scales and pressure gauges that I don't have. I see the FSM does have the instru toons for that procedure though.

The Chilton's manual advises to have a reputable shop perform that adjustment, and that would be the case for me.

Blue1991

To be clear, "BMC, then RR, LR, RF, LF, then LSPV", that is the bleed sequence.

Adjusting the LSP-BV (sorry I keep using different letters for it [the load sensing proportioning and bypass valve]) requires some scales and pressure gauges that I don't have. I see the FSM does have the instructions for that procedure though.

The Chilton's manual advises to have a reputable shop perform that adjustment, and that would be the case for me.

Sturmcrow

If I were you, I would bleed the LSPV first before futzing with the master cylinder. I am really surprised that it took 3.5 weeks for someone to finally post to you strongly suggesting that you double-check that the LSPV is being bled. If the tech. that worked on your truck is not familiar with these trucks, that would be exactly the thing he would miss. Any gomer can bleed the master cylinder, so surely he would not have missed that. I've bled a lot of car brakes myself, and on my truck it was the LSPV that I missed the first time too (and spent several days and quarts of brake fluid trying to figure out why my brakes were crap)

There is a spec in the FSM about how many clicks your parking brake should make when you pull it out (I think it's 11-17, assuming the same as the pickup). If you are still getting a lot more clicks than that, your rear drums are still maladjusted. Having them too loose will give exactly the symptoms you describe (particularly having the pedal travel over an inch before feeling pressure build up). The rear brakes are not that hard to adjust yourself. I would jack up the wheel you are working on and tighten the brake until you start to feel some drag when you spin the wheel.

That said, having just read through the entire thread for the first time, much as Blue1991 did, I really think your LSPV was overlooked by the shop, and they do not know how to adjust rear drum brakes.

Nuyota

Sorry for lagging so long in response. I put off doing anything on the truck for a while. Then the rebuilt BMC started leaking and the spongy brakes started getting worse. FYI, every OEM rebuilt BMC I got leaked. Went through about 4 different ones, all leaked. Ended up using a new centric BMC. And the shop did their best to try to help me out and replaced the leaky BMC no charge, etc. So now the brakes are at least consistent, but still spongy. So now we're kinda back to square one where everything has been replaced but spongy brakes. I've been lagging on checking things out myself cuz I've been working on various other projects. I will do the above checks and bleeding mentioned above myself sometime soon, and I have definitely noted the LSPV. Thanks for all the help guys, sorry I'm taking so long to follow thru on the advice.

Dogpound13

I know this thread is pretty old but I just went through this exact same thing. I ended up having to finish what the shop started. You bleed driver rear then passenger rear then passenger front then driver front and then most important after finishing all brakes you bleed the load sensing proportioning valve located on the frame passenger rear with a rod crossing down to the axle housing. After doing this exact step I have full pedal and awesome breaking, ebrake adjustments are important also, you should be able to get one full rotation on your rear drums but no more, I went with a half turn myself and all is stopping and holding my truck in place perfect now. If your truck is lifted you may need to fabricate a taller bracket from your axle or bend the rod up that goes to the LSPV. The gap between the rod and the valve is minimal but should be close as in not quite touching while no load is in your truck.

Dogpound13

If all brakes have been bled several times you might be able to just bleed the LSPV, a friend pumping the brakes like five times and you open the bleeder, you should get all the air out the first time but I'd bleed fluid through it a few times to be sure.

bowtierebel

Old thread, but I'm reading it, so someone else might too. I just replaced many brake components in my 1986 4x4 truck. I did everything per the manual and had great pedal pressure until I started the truck. Pedal would go to the floor and the truck would bog down and die if the brakes were pumped. I could here a "hiss" every once in a while. I started with the simple, although aggravating, vacuum leaks before replacing more parts. I did not see that anyone mentioned what I found. The shop you used sounds poor at best and if they replaced this part then it may be the problem. Check out the check valve in the vacuum line going to the booster. Make sure it is not only good, but is installed correctly. If there is an arrow on it, the arrow should point towards the booster. It is supposed to allow vacuum to build in the booster, but not bleed back into the manifold when the truck is shut off. I installed it correctly and all seems good. I can't drive it yet (project) because it needs a clutch kit. I found this important bit of information right here on this site. Awesome guys and great help. Only thing I can't get quite right is the stop bolt adjustment on the bellcrank. I think the parking brake cable may be stretched because when I get it to where it holds good, the bolt is about an inch away from the back of the drum housing with the bolts as far out as they will go. New shoes too. Maybe someone will see this new response and chime in before I start a new thread or find the answer in another thread. I hope you finally got your truck straightened out.

Nuyota

Well, finally had the issue resolved. Took it to the truck shop and they swapped out master cylinder for a new oem one and works fine now with normal pressure. Problem was it wasn't the right size diameter. Previously I had tried rebuilt oem one and new cardone one. They both appeared to be correct with fittings in the proper place and part numbers supposedly for turbo 4runner but both had the smaller diameters. Freakin hate trying to get the right parts when all the manufacturer information is incorrect.