Can’t bleed these damn brakes!!! (1 Viewer)

[Jcarr210]

About a year ago On my 62 i noticed the brake pedal getting spongy and didn’t have time so parked it in the back of my carport.

Recently I replaced the rear brakes and wheel cylinders. While bleeding I wasnt paying attention and ran the master cylinder dry. I bled the master cylinder and then ran a quart of brake fluid thru the LR wheel cylinder because the old stuff was pretty nasty as I read people going they a lot of brake fluid bleeding these things. I then went in order including that LSPV and Ive spent the last few hours but can’t get the pedal right.

If I pump it up the pedal gets hard and will stay hard for the 5 minutes i held it down and it never went down. If I let go and hit the brakes quickly also no issues but if I don’t touch the pedal for maybe 10 seconds then hit the brakes then it goes right to the floor until I pump it a few times.

I have braided brake lines that aren’t leaking and checked every connection and there are no leaks. I pulled the master cylinder away from the booster and it’s not leaking out the back of the master cylinder. I’m at a loss and can’t figure out what’s going on. Any help would be greatly appreciated. Thanks in advance.

 

[RodrigzCrzr]

On a 62 series you have too bleed a proptioning valve that is in the center of the truck underneath.
Try that. But I think there is a sequence you may need to follow.

 

[NMfjCruiser]

I use a pressure bleeder I made with a cheap bug sprayer and an old master cylinder cap. Works every time even on systems that are notoriously hard to bleed. I still use the normal bleeding procedure but having the reservoir pressurized seems to help.

 

[Freewheel]

how old is your master cylinder? It can fail erratically like you are describing without having any external leaks.

 

[Jcarr210]

So I pulled the drum off and the rear brakes didn’t adjust at all using the hand brake. It got dark on me but I’m going to try and adjust them from the udjuster in the backside. I’m wondering if that’s why I have to pump up the pedal to get brakes.

 

[LAMBCRUSHER]

Adjust them all the way out so there is no slop in the shoes and you can’t turn the drums. Then bleed. If it ran dry, start by bench bleeding, then doing the prop valve, then the left followed by the right rear wheel, then the front right followed by front left. If that doesn’t work, you may have to dig into tipping the cups. It is a last resort type of thing I won’t explain further in here.

 

[g-man]

The emergency (hand) brakes are notorious for freezing up at the spring on the backside of the rear wheels where the cable comes in. They corrode in place esp. if you don't use them regularly or lube them occasionally. If they are froze the brake shoes wouldn't move. Look for the lever on the back side of the wheel to move...spray lube, hammer, pry bar...etc to free it up. Froze up emergency brake should not affect the function of hydraulic brake system.

As far as the hydraulic brakes ...x2 on the master cylinder having an internal leak or possibly you need to remove it and bench bleed it since you ran it dry.

 

[fjdemon]

x2 on bench bleed

 

[Willard]

While the old tried and true method of pump the brakes three times and then hold works. I find the pressure systems work best. I have a commercial unit and it bleeds the brakes perfectly.

I agree with the bench bleed on the MC again. I am not sure if the proportional valve has a bleeder on it. If it does then hit this first after you bleed the MC. Then follow the procedure for everything else.
If you still have spongy brakes or they go to the floor, you may have a leaking line somewhere.
If running and spongy then you could check the booster, but I would leave that as a last option.

These system are almost as basic as they get for hydraulic brakes.

 

[Jcarr210]

So I went out and bench bled the MC, adjusted the rear brakes, adjusted parking brake cable, lubed up the bell crank, flushed about 2 quarts of brake fluid through the system, and bled it in the correct order...all 5.

With the vehicle off it has a much better pedal and gets very firm quickly and the pedal never sinks even after holding it for 5 minutes or more. No more pumping it up to get a firm pedal. Having said that when I start the vehicle if I push hard enough I can feel and hear it bottoming out though the pedal is still about 3 inches from the floor. I took it for a quick spin and it stops decent enough but if it were an emergency panic stop type of situation there’s no way I’d stop in time. I even pulled up the hand brake then hit the brake pedal and still it bottoms out 3 inches from the floor. I’ve checked every connection and there is no leak and pumping up the brake pedal has zero effect so I’m confident there’s no air in the system. About the only thing left to do is replace the master cylinder. Sound about right? Am I missing anything? Thanks in advance.

 

[cruisedeisel]

I feel ya dude! I just did a rear disk upgrade and I have.... Deleted proportioning valve and added and after market one. Replaced MC. Replaced Booster. bled properly and still no go. Well no stop. Anyways... Good luck!!! Sorry I cant help.

 

[Super77]

OP, I've got the same situation on mine. Rebuilt the calipers, replaced all the soft brake lines, replaced the rear pistons, took apart and lubed all the rear mechanical bits, bench bled and replaced the MC, bled all 5 points, tested the booster, flushed a gallon of fluid through using just about every method available (2-person press-and-release still works best) and I still can't lock up the front wheels on dry pavement. Even had it all double-checked by my mechanic. I think we're just used to better brakes on modern cars. A friend with an 80 swears that SS brake lines will firm things up due to less expansion, and I'm considering an MC upgrade from a T100.

 

[lechnito]

@Super77: Over the last 2 years, I upgraded to SS brake lines everywhere, T100 MC, 4runner calipers + booster, slotted/drilled rotors, etc. At this point, the only original brake parts are the pedal, hardlines, LSPV, and the e-brake parts.

Brake performance is now excellent and while I can brake pretty damn fast, I doubt the fronts will lock up on dry pavement in a panic situation. My guess is that deleting the LSPV would help me achieve maximum braking power, but I also suspect that removing the LSPV would result in potentially dangerous braking behaviors under certain scenarios...

 

[Jcarr210]

Well my issues are with ss brake lines already but I found the problem. So I put on my big boy pants and really stomped on the brakes and got it to lock up. I then thought about it and even from light stops I’m pushing harder than I should have to. It was sitting for 2 years and I’m guessing the booster is taking a dump on me.

 

[LAMBCRUSHER]

makes more sense...when this happened to my wifes 62, I put an inverted 4runner booster and inline check valve in it. cost about 80 bucks used. just make sure to set proper clearance between the pedal to new booster rod, and the new booster to MC rod. IIRC, I had to cut about 3/8" off the pedal to booster rod...HTH

 

[cps432]

makes more sense...when this happened to my wifes 62, I put an inverted 4runner booster and inline check valve in it. cost about 80 bucks used. just make sure to set proper clearance between the pedal to new booster rod, and the new booster to MC rod. IIRC, I had to cut about 3/8" off the pedal to booster rod...HTH

Where does this check valve go?

 

[Randy88FJ62]

The inline check valve is on the driver's side firewall and about 18 inches before the inlet to the booster. It's a small cylinder about an inch long with two male nipples on it that accepts the vacuum line. Vacuum line is measured in fractional increments of 32nds. Make sure your vacuum line has not been replaced by some other type of hose. A collapsed line will feel like your brake booster is going out.

Explain your bleed order: LSPV is supposed to be last. (is your truck lifted? If so, was LSPV lifted to compensate?)

I have to press the pedal hard to get maximum braking force out of my braking setup.

My setup:
T100 MC
T100 booster
All soft lines are braided Stainless
4Runner front calipers
FZJ80 rear calipers

 

[cps432]

The inline check valve is on the driver's side firewall and about 18 inches before the inlet to the booster. It's a small cylinder about an inch long with two male nipples on it that accepts the vacuum line. Vacuum line is measured in fractional increments of 32nds. Make sure your vacuum line has not been replaced by some other type of hose. A collapsed line will feel like your brake booster is going out.

Explain your bleed order: LSPV is supposed to be last. (is your truck lifted? If so, was LSPV lifted to compensate?)

I have to press the pedal hard to get maximum braking force out of my braking setup.

My setup:
T100 MC
T100 booster
All soft lines are braided Stainless
4Runner front calipers
FZJ80 rear calipers

I just upgraded to the t100 MC, 4Runner booster but kept stock drums, rotors, and calipers. My soft lines were replaced with new rubber lines. I’m also in a 60 rather than a 62. I’m guessing this check valve isn’t in the 60?

 

[Randy88FJ62]

The 60 LSPV is mounted on/near the booster and is fixed rather than adjusting as the 62 is. So different bleeding sequence for the 60 / 62.