Never Ending Brake Bleeding

3/4 ton, heavy drum brakes in the rear ('77 Cheyenne), brake booster

Replaced brake cylinders, bleeding them and they won't stop! You think all the air is out and then BAM, milky fluid, or big air pocket. 3 PINTS through the system! We're not running the master dry, there's no other leaks in the lines anywhere.

My dad says he's been through this before, says at times he's run 5 GALLONS through cars at work before they get the air out.

We've got a trip this weekend, planning on taking the truck but we need a pedal!

ANY IDEAS??

Collapsing rubber lines? Bad brake booster? I once bought a 91 plymouth sundance at auction and my dad put so much money and time into the brakes to no avail. He got pissed and trashed that car then sent it to the junkyard, never did figure out why it would never get brakes

78C10BigTen said:

Collapsing rubber lines? Bad brake booster? I once bought a 91 plymouth sundance at auction and my dad put so much money and time into the brakes to no avail. He got pissed and trashed that car then sent it to the junkyard, never did figure out why it would never get brakes

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I mean everything worked as it should before we did the swap.

Last time we bled the back we were replacing the rubber hose at the diff and i do remember it taking a bit. But worked great ever since.... what are signs of bad brake booster?

Powerhouse Ranch said:

3/4 ton, heavy drum brakes in the rear ('77 Cheyenne), brake booster

ANY IDEAS??

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First, you must bench bleed the master cylinder. You can do this on the truck too. If you need to know how I will explain.

Second, and very important, the rear brakes need to be adjusted properly. If they have too much travel you will never get all the air out. You can cheat this by applying the e-brake and remove the extra travel. If you apply the e-brake and the drum still turns, the shoes are way out of adjustment.

Note: The automatic adjusters will not work to take out all the slop if the Shoes were not adjusted when installed. They are designed to maintain proper adjustment only.

Turbo4whl said:

First, you must bench bleed the master cylinder. You can do this on the truck too. If you need to know how I will explain.

Second, and very important, the rear brakes need to be adjusted properly. If they have too much travel you will never get all the air out. You can cheat this by applying the e-brake and remove the extra travel. If you apply the e-brake and the drum still turns, the shoes are way out of adjustment.

Note: The automatic adjusters will not work to take out all the slop if the Shoes were not adjusted when installed. They are designed to maintain proper adjustment only.

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yeah the adjustment might be off. might have to look at that. didn't know that if they were out of adjustment that they'd screw the air up... makes sense though now that you mention it

Part of the reason I like vacuum bleeding…

Adjust the rear brakes, doubled check lines are tight, can try just gravity bleeding and let the air work out, put speed bleeders on the wheel cylinders(all my car get them now), use mitty vac and or get a pressure bleeder setup.(can make one with a weed sprayer also google it) once you know it's clear good fluid I just put the line in a bottle recycle the brake fluid back into the master cylinder so I'm not wasting $$$

I'm going to preface this by saying I've been drinking quite a bit so hopefully I'll be able to write this out and have it make sense. Vacuum bleeding is great and faster than gravity, but gravity will do the job just the same. I'd gravity bleed it good and see if there is petal after that. It is also possible that if the master cylinder was not healthy to begin with that the pumping for bleeding has done it in. It is possible sometimes to have air suck into the master cylinder especially in a situation where you can't build pressure to begin with. Specifically it would be at the seal for the booster. If this seal went bad when your driving you'd suck fluid into the booster with the vacuum. Gravity or vac bleed it then see if there is petal. Once you have some petal at least you may find that there is leak as well. That's what I think and how I'd tackle it. These trucks have a really simple brake system and there should be no where for air to get trapped like in newer rigs with ABS modules. FYI I've never found the need to run anywhere near 5 gallons of fluid though a system to get the air out. Maybe a couple of pints on a bad day.

Actually this is a situation where a pressure bleeder would be really great. Not only will it push all the air out, but if you have developed a leak somewhere you'd see it. I don't even have one at the shop......

@Powerhouse Ranch

Did you succeed at bleeding the brakes?

If you still have an issue, you may have a problem with the proportioning valve.

Turbo4whl said:

@Powerhouse Ranch

Did you succeed at bleeding the brakes?

If you still have an issue, you may have a problem with the proportioning valve.

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hey thanks for following up my friend! yeah come late Friday night when we were packing for the trip, we decided to bleed on it more and there was still quite a bit of air. After a while and still having a tiny bit of air, my brother said he liked the pedal, took her out for a ride and came back with a smile on his face. the next day we drove 70 miles to the camp and it was an absolute champ as expected, no issues. then followed by another smooth 70 back. I still ask the question "hey you've got a hell of a truck. can i have it?"

He obviously says no. darn. maybe some day! Got some epic camp pictures for all you pictures ******!

Powerhouse Ranch said:

hey thanks for following up my friend! yeah come late Friday night when we were packing for the trip, we decided to bleed on it more and there was still quite a bit of air. After a while and still having a tiny bit of air, my brother said he liked the pedal, took her out for a ride and came back with a smile on his face. the next day we drove 70 miles to the camp and it was an absolute champ as expected, no issues. then followed by another smooth 70 back. I still ask the question "hey you've got a hell of a truck. can i have it?"

He obviously says no. darn. maybe some day! Got some epic camp pictures for all you pictures ******!

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That's a damn nice truck! I'm such a *****!!!!!!

Pressure bleed or vacuum bleed is the only way to go. R u using correct procedure....bleed line furthest away from master or longest line and proceed thru all 4.

Allan Abley said:

Pressure bleed or vacuum bleed is the only way to go. R u using correct procedure....bleed line furthest away from master or longest line and proceed thru all 4.

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yeah, was doing it right

Nice truck! I like the all white rims to, and the flush camper shell. So what happened that it seemed to be okay now? I use a Mighty Vac to do all of mine and the one thing I've noticed is what may look like air in the line could be a slight leak where the hose is over the bleeder. The air isn't coming from the line, it's leaking at the end of the hose where it's slid over the fitting, it just looks like it's still got air in the line, when the air is coming from the hose being just a tiny bit loose.

I've got some spark plug wire clips that snap over the end of the spark plug, those banded little clips some plug wires have on them, from an old set. And I have that on the end of the hose and it snaps over the end of the bleeder just like a spark plug and holds the hose tight!
Sometimes it's hard to see if it's the hose or there actually still is air in the line.