Sketchy Brakes

[ChrisInVT]

Replaced most of the braking system in my truck and it still has sketchy brakes... Everything but the master cyl and proportioning valve has been replaced - and I've bled the brakes in the proper order. For a while I've been driving it with a real soft pedal. The brakes wouldn't catch until about 3/4 of the way down, and then when they did catch 50% of the time you would eat the dash, the other 50% it wouldn't stop the truck - just slow it...

Well, today while I was changing my leaf packs, I snagged a rear line and had to replace it. After I completely bled the brakes, they ended up worse then they were to begin with! I went through a whole quart of brake fluid making sure there was no air, and that system has to be free of air and moisture with that amount of fluid!

Now when I hit the brakes, the pedal is REAL hard to push down (like if the truck wasn't running), and it barely slows the truck down at all. I tried panic stopping from 30MPH, and it took a few hundred feet - at 50MPH forget about it! Whatever would stopped in front of me, would have a very unhappy appointment with my bumper. If the truck is off, forget it - you can't even move the brake pedal.

This is a new kind of WTF for me. At first I thought the master cyl was gone, because when at a stop sign/light the pedal would slowly go right to the floor until I didn't have brakes anymore... But now it's the complete opposite.

[ChrisInVT]

Well, after a few days the brakes are back to being spongy as fvck, and not engaging until the pedal is 1/2 to the floor....

[lt1s10onair]

are you getting sufficient pressure through the bleeders? the hard pedal is usually a sign of a bad brake booster, or a large vacuum leak to the booster.... are you losing any fluid?
id look towards the master cyl..... abnd while ur there, check and make sure its not leaking into the booster, cuz then its f**ked

[ChrisInVT]

I still think it's the master cyl also. Three of the bleeders are getting good pressure (the rear right bleeds harder than the rear left, but when I hit the brakes both rear tires lock up at the same time). Not loosing any fluid either. On my old '87 caprice, when the booster went bad I was loosing fluid

[ChrisInVT]

Sweet, an update...

So now my front left tire locks up about 3/4 way to the floor. It scared the shit outta me at first, because I've never been able to lock up the front brakes, just the rear... And on dirt

[greencactus3]

need new calipers possibly

[ChrisInVT]

Well to update this again....

I replaced the Master Cyl about a month ago. Along with that I re-adjusted my parking brake. I pulled the drums off the rear and inspected the pads, cyls, hardware and drums, all in good condition. Pulled the calipers off the front and inspected them along with the pads and rotors, all good. The brakes were excellent for about three weeks. They were very touchy and I could easily lock them up.

Over the past two days that I've been driving the truck, almost the same shit as before. You can press on that pedal as hard as you want, and the truck doesn't stop, just slows down like the brakes are wet. When backing up in reverse and using the brakes, they make a weird squeaking noise. It's not a high pitched squeal/squeal, but a low pitched one - again like if they were wet.

At this point in time, EVERYTHING has been replaced. New Master cyl, new rotors, new pads, new calipers, new drums, new wheel cyls, new rear pads, new drum hardware, new lines. No vacuum or brake fluid leaks anywhere. Re-bleeding the system doesn't seem to do shit.

It's going to be fun trying to stop when I get the 33's too, thats going to make it SO much worse.

[ChrisInVT]

Well to update this again, I have basically no brakes at all. The pedal goes RIGHT to the floor and the truck coasts to a stop. I have to manually downshift from drive to 2nd to 1st to get the truck to slow down, because I'm basically driving around with no brakes. This is fun now that I have to move and I have the bed loaded down with stuff and then a bunch of shit on the roof rack.

Everything has been replaced.
The system has been bled upwards of 15 times.
The parking brake has been adjusted.
All the fluid is new.
I'm getting extremely annoyed.


I looked in the master cyl the other day, and if I pump the brakes to the point where they don't work at all (the more/harder you press the pedal, the less they work) they'll be thousands and thousands of little bubbles in the fluid. Air in the system makes no sense since it's been bled so many goddamn times.

[V8Blaze]

my old nova had a very similar problem. THe original owners of it also had the same issues. changing the master cylinder always fixed it for about a year, i think i put two masters on it in 5 years, and one was put on a few years before i got it. I had a few people tell me to replace the proportioning vavle. But we never found out what the deal was with it. It sat for about a year last time i drove it and the brakes were back to garbage. If you find out the problem, id love to know. Also the brakes on my blazer suck too, but im pretty sure all parts on it are original lol

[ChrisInVT]

My brother came over and checked it out yesterday. He's ASE certified and all that good shit. We re-bled the brakes and it got worse. He's at just as much of a loss as I am.

[lt1s10onair]

first, if youve replaced all that stuff already.... f**k it, replace the front brake hoses..... theres a good chance that they are broken up inside.... are you pressure bleeding the system, or gravity bleeding it? if you are pressure bleeding it, how is each wheels pressure? also, this may sound dumb to ask, but did you thoroughly clean the rotors and drums before putting them on? there is a coating on them to prevent rusting, while sitting on a shelf.... if you dont clean them thoroughly (usually with carb cleaner) then, u will destroy the pads and/or shoes, by gumming them up with a slippery material.

[ChrisInVT]

Replaced those already, the only thing not replaced is the vacuum booster - and it has the problem whether the truck is running or not so I don't think that's the cause. I'm pressure bleeding them, and they all seem to have the same amount of pressure. And yeah, everything was cleaned. When I got the truck the brakes sucked so I slowly replaced EVERYTHING chasing this f'n problem.

[lt1s10onair]

i cant see a vacuum booster giving a spongy pedal..... hard pedal id understand..... if you go on dirt and mash the brakes, which ones lock up?

[ChrisInVT]

none of them

[tt85_GM]

do the wheel cyls move freely?
I know you've bled them, but sounds like air is still trapped somewhere or your leaking fluid somewhere.
Does the brake fluid go down after a few days or weeks?

[ChrisInVT]

Yeah, everything moves freely. It acts like there is still air somewhere in the system, but I don't know where it can be. I bench bled the master cyl before installing it. And after I replaced that and re-bled the system the brakes worked decent for a few miles, and the more I drove the truck the worse they got. It has no leaks (I would have noticed it on the garage floor or the lines being wet when I'm under the truck) and the brake fluid level hasn't moved a bit since the last time I bled the system.

[tt85_GM]

Did you let it gravity bleed for hours?
And this may be stupid but..did you make sure you took off any plastic covers or anything they use to ship the parts with, sometimes they put those plugs inside lines or calipers to keep moisture out. That can cause big issues like what your having.

[ChrisInVT]

Alright, so here's the deal... I was out wheeling last week and my passenger rear wheel cyl had a catastrophic failure. Before I could crimp off the line the master cyl bled itself dry...

Well I replaced the wheel vyl and damaged section of line and attempted to bleed the brakes. Key work here is ATTEMPTED. After 4 hours of bleeding and about a gallon of brake fluid - there is still air in the lines. This is pissing me off beyond belief!

I finally gave up (after running out of brake fluid), and the pedal still (obviously) goes right to the floor. BUT, it's not "squishy" like it use to be. It goes right to the floor like when you have a bleeder open. As soon as it's about 1" from the floor the brakes grab hard enough to chirp the front 33's - not lock them up, but make them squeal a little; so I'm getting closer.

I think that the problem is the disc brake proportioning valve has air in it, but there's no bleeder on it. I suppose I can disconnect the lines and do a similar procedure to bench bleeding the master cyl, but that might be a huge PITA. So far everything but the proportioning valve has been replaced, so I'm confident that may be the culprit, and it wouldn't surprise me if there's air trapped in there and that's been causing my problems all along.


Anyone have any tips on bleeding it, or any thoughts to add?





Edit: For anyone that doesn't know what the proportioning valve is:

[Speedy2222]

any more luck on this? i have sort of the same issue... i think i may have more of shitty/worn out brakes than anything else, the pedal has to go almost all the way to the floor before it stops the truck and holds it there

[ChrisInVT]

Nope, nothing. I haven't had the time to put another gallon of brake fluid through it to see if i can get the air out.