jerry507

I'll start with some back story. I have a 95 pickup 4wd, but the rear axel is off a 1 ton. I was having some confidence issues with my brakes. The front looks good, nice pads with plenty of width and I don't have any doubt about them. The rear always seemed iffy. No ebrake and the hardware seemed locked up. Braking always pulled to the right, and I felt like I wasn't getting ANYTHING out of the back.

So now what I did. I ripped apart both drum brakes. After a lot of confusion about the rear axel, I bought all the right replacement hardware. 2x wheel cylinder, new shoes, new hardware kit. Everything was cleaned up and broken loose. I regreased everything with both lithium grease and high temp grease where indicated in the FSM. Next I replaced the master cylinder (it was cheap enough). I bench bled it, and then bled it again later on. I've bled the entire system about 4 times.

Now I can't seem to get a good firm pedal. I can REPEATEDLY push the pedal nearly to the floor. It never firms up and behaves exactly the same engine on or off. The brakes do seem to work, and it feels like if I just push past the initial lack of resistance, they brake fine. I don't know what "spongy" exactly feels like, but it doesn't seem like there is a steady increase in pressure. More like nothing, then brakes start to engage. I've bled over and over, including the prop valve (not that it probably works anymore). I've pushed the adjusters all the way out so you can't even move the drum normally, no change.

This is driving me absolutely insane, and I've been troubleshooting it for days. Any bright ideas and I'll try them within 24 hours Thanks!!!!!!!!!

combatcarl

Maybe a bad master cylinder? Not too likely, but that's how my non boosted 65 f100 was until I replaced and bled everything...much different system tho...

jerry507

It's a brand new master cylinder. It seemed fine when I bench bled it. All that I can really say is that it didn't leak out the rear. Incidentally I was just looking at the FSM master cylinder chapter and I noticed there is a gasket between the MC and the booster. I would assume that might cause a vacuum leak, but wouldn't cause a soft pedal.

yotarover

haven't ran across one with a gasket, between the mc and booster. Just put rtv around it and stick it on. Gonna assume you bled the LSVP,

Roofmaster

I also had an issue with a spongy pedal when I replaced my rear axle.I too bled the master cylander,calipers,rear drums and proportioning valve like three times,at least.Couldnt figure it out,Ive done dozens of brake jobs on all makes and models including my other Toyota trucks.I had the rear brake self adjuster tight like you say you have youres,well that could be youre problem.When you adjust it so tight that the drum just barely moves sometimes inadvertantly you can knock the wheel cylander plungers or in my case just one plunger off the brake shoe.Youll still have brakes,and wont be losing fluid anywhere but it will go to the floor because the piston in the wheel cylander is pushing out but not actually pushing against the shoe itself.I loosened the self adjuster and pulled the drums and sure enough the drivers side cylander had dislodged itself from the shoe and was just pushing air.I popped the shoe back on the wheel cylander put the drum back on and barely tightened the self adjuster and didnt F with the drum from that point for fear of dislodging the shoe again,just put the tire back on and brakes were solid as a rock.Might not be youre problem but its worth a shot,nothing like having the confidence of a solid brake pedal.Good luck brother.

Roofmaster

The wheel cylander didnt dislodge from the shoe as its stationary,the shoe dislodged from the wheel cylander but same principal.It was because when I tightened the self adjuster I kinda messed with it a little to make sure it was tight,by turning it by hand and pushing and pulling on it which dislodged the shoe from cylander.

jerry507

I'll take the drums off tonight and double check that the pistons are still seated on the shoes. I'm reasonably sure they are but it's better to double check...

One question about adjustment. My autoadjusters no longer seem to work right. The lever is always pulled too tight so it doesn't bite into the teeth anymore. This kind of sucks but I'm not sure exactly what's wrong and it's a huge pain to find parts to fix them. However this means I've just been adjusting them myself. I set them all the way in, give the adjuster a little flick and see if I can spin the wheel. When I feel the shoes start to bite, I just back it off a turn or two. Does that sound reasonable?

The other thing I noticed this morning, which I forgot about, is that my pedal does sometimes feel firm. It seems like randomly it will firm up, and stay firm with good braking power (essentially just the same as before but without the huge area of no resistance before getting to the braking region) until I really push down on it hard. Then the pedal just... gives way, with exactly the same braking power. It will stay soft until randomly resetting.

This was actually the main reason I decided to start working on the brakes. I figured the MC was sticking, or a piston was sticking in the back. Either way it seems to brake the same, it's just a pedal travel issue that is really scary.

Any ideas?

jerry507

I drove half the morning drive and the entire way home with a relatively fine pedal. If I press too hard the pedal gives way and I get a ton of travel.

Arg, this is really annoying.

YotaRunner33

What happens when you slam on the brakes say going 30ish mph? In a safe location of course lol.

Sometimes that fixes a spongey pedal after you have bled the system.

jerry507

YotaRunner, the pedal does absolutely nothing for a while and then all the sudden gets all it's bite back and I can just about or actually lock the wheels depending on how crazy I am.

I checked a couple things and got some interesting results. A friend wanted me to make sure the rubber brake lines weren't flexing, and they're not. I looked at the wheel cylinders and they're definitely seated properly. I checked adjustment and they seem... well reasonable but maybe not ideal.

But the best part is that I tried to bleed the system again. I started at the rear driver side and... nothing. The brakes were still "hard" as I described a post or two ago and just nothing came out. I tried rear passenger, same thing. I successfully bleed all four wheels and the load sense valve 4 times and now I just can't get anything. The front brakes had fluid flowing too.

So I started seriously bleeding the load sense, and I managed to get some more air out. My load sense valve is really rusty and crappy looking, but also the spring arm doesn't look like it's adjusted at all if I compare to image BR3278 on page BR-65 of the FSM. The arm is much further down. I wonder if that valve is just either not working or has a bunch of air in it.

Anyway I got overzealous and bled the reservoir dry so I'll have to bleed the entire system again anyway. I'll make sure I do a really good job and see what happens.

abecedarian

I wonder if the brake booster is working right and/or the pushrod from the pedal is adjusted properly.

TrikeKid

New or not, that sounds like a bad master cylinder to me.

jerry507

So after running the MC dry (opps), I had to rebleed the entire system. As I said, I wasn't getting anything out the rear bleeders. I was wondering if the prop valve was screwing things up, so I undid the nut at the end of the spring arm and fiddled around with it.

It turns out the strange feeling I was getting, where it would be hard until I pressed too hard and then would suddenly give way, was from the prop valve. It must be somewhat non-functional or just had a LOT of air in it. I had bled the prop valve last, and just did it until I got two full pedal presses without any air. After taking the spring arm off and jiggling it up and down a bunch, I got a ton of air out of the valve.

After rebleeding the entire system with the valve suitably jiggled, it now brakes properly and it doesn't seem to give way anymore. I think at various points there was air in different parts, especially the MC at the beginning, so a thorough bleed is essential to even starting the troubleshooting process.

abecedarian

Wise words.

lastname_firstname

This is all good info as I am having the same problem and have been stumped for the past 2 days. I plan on trying this tommorow and hopefully have the rig working for labor day camp trip

ehenson99

I'm having the same problem with my 88 pickup after replacing the brake shoes in the rear. Now I got a pedal that almost goes to the floor and i've had the shoes adjusted really super tight and super loose and it doesn't change anything. I did adjust the prop valve arm to the highest position but that didn't change anything either. I haven't bled anything yet but shouldn't have to as it was fine before the shoe change. This thread has some good info and I think i'm gonna bleed the prop valve and work the arm up and down and see if that changes anything.

Innocent Fool

I just went through this last summer. Tried bleeding the thing for three days. The only thing that worked for me was vacuum bleeding the system. Look on youtube for vacuum bleeding and how to make one. It's not that hard. Once I made a vacuum bleeder I used it on several different vehicles. It's surprising how much air can be trapped in a system and it's WAY more enjoyable bleeding with vac.

It's the only thing that helped me get pedal

dvaldi

Interesting...jiggle the handle. Just replaced my LSPV (used) and all the lines from the ABS actuator rearward. Used a Motive power bleeder, which works great, and bled the lines 4 times. Still have symptoms like jerry507 but no bubbles. The e-brake cable snapped as well as I was working on the brake lines...trying to be safe. From what I've read in other posts, I need to get the e-brake installed/calibrated then see if I still have the same problem, if so? a little jiggle.

Millhouse

Did you ever find the solution? I think I have the same issue

jerry507

I am actually living with this issue to this day. I've replaced everything except my booster, the lines and the LSPV now. It wasn't really in an effort to fix this particular problem, more because the fluid all over this system was absolutely terrible and it ruined the rear wheel cylinders (replaced at the time of the original post) and the front calipers. Subsequent work sent the calipers over the edge and I just replaced them.

My best guess right now is that my LSPV is completely crapped out and whatever is wrong with it is temporarily fixed by bleeding it. Either that or my booster is crapped out. Either way, I get great brake pressure and the truck is safe to drive. The brakes just FEEL wrong. LSPVs are expensive and I haven't sunk the money into replacing it yet.