Assistance needed: Brake bleeding

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procomsignathid

procomsignathid

Basket Caseworker
SILVER Star
Joined
Mar 12, 2025
Threads
16
Messages
376
Location
Colorado
Hello all-

I replaced my rear brakes this weekend, been running into an issue. Where I'm at now is that it takes a few pumps to build/hold pressure while the truck is off, Im not getting any air bubbles so it seems fine. But when I turn the truck on, pedal basically goes to the floor.

Here are the details I know:
  • 1978 FJ40 (mfr 10/77), with 2 wheel cylinders on each rear drum. discs up front.
  • Brakes were working prior to this weekend. Working in that the truck stopped just fine, but I noticed the rear reservoir was empty a week or so back and topped it off. Hadnt noticed a leak / drips since.
  • This weekend I replaced the following:
    • New wheel cylinders / pads / springs / drums on rear brakes, as well as soft line between chassis and rear axle
    • Front brakes untouched
    • Ensured that wheel cylinders were in the right place:
      • Left front (with the bleeder) adjustment wheel facing up, ramp angled back towards hub
      • Left rear (no bleeder), adjustment wheel facing down, ramp angled towards hub
      • RIght front (with bleeder, reverse thread adjuster), adjuster wheel facing up, ramp angled back towards hub
      • Right rear (no bleeder, reverse thread adjuster), adjuster facing down, ramp angled back towards hub
    • I adjusted all wheel cylinders:
      • made em as tight as I could (keeping them as even as I could eyeball it) while still getting the drum on
      • adjusted each cylinder wheel to tighten them further (with the tool, pulling away from the axle tightened on all four) until the drum wouldnt move
      • backed off 5 teeth
Since doing that work, I was worried that while bleeding I pushed the pedal too far down and the excess travel might have broken the master cylinder seal if there was any crud in there. So i plugged both front and rear outputs from the master cylinder (spare brake line, crimped), and with the engine on the pedal stayed put. So I think the master cylinder is fine.

Since doing that test, I have reconnected the front and rear lines, and bled all four corners repeatedly while my wife operates the brake pedal. Just as I said up top, pedal takes a few pumps to stiffen with the engine off, and with it on it sinks right to the floor.

Any help would be much appreciated!
 
5 clicks backing off is too much … imho do 3 clicks

Also if you used aftermarket cylinders in the rear they are notorious for air and not bleeding well…

You didn’t push the pedal too far

Readjust and rebleed

I have better luck pumping myself and using a bar to hold the pedal … then bleed

She might not be really pushing enough … have her think of some dumb s*** you did recently while she’s doing it might help :meh: But…. Still not as hard as you’d be able to push
 
Btw I recall some taking the top of rear cylinder off

Found this post that explains what to do:
WyoMike said:
Thanks everyone for the input.

First off - I did not bleed the MC before I installed it. Didn’t know about that until it was pointed out to me.

Last night I found more information on other mud members with the same or similar problem with CCOT wheel cylinders. I agree with everyone there has to be air in the system. So before I try anything else, I decide to pull apart the rear wheel cylinders.

It was recommended to install the plastic cup vertically until submerge to insure no air was trapped there. No one had photos so here’s what I did and what it looks like:
View attachment 3710684
View attachment 3710683
Second photo is hard to see but I’m installing the cap/cup vertically.

I did this to both rear wheels and bled the brakes. What a difference! I had brakes!
Brake pedal goes about a third down before pads move but they try to brake. It does take two pumps of the pedal to get good stopping power.
Click to expand...
 
best way to bleed is to purchase a brake bleeding unit one that you attach a hose and pump the bottle to 12psi. I had the same problem and this worked better cause it really ads pressure to the system and pushes the air out.
 
looking thru responses. Just wrapped up for the night, still same issue. I have a chinesium master cylinder showing up at NAPA tomorrow as a stop-gap just in case, but Im pretty convinced its not the master at this point. My earlier test with the plugged/crimped lines and pumping/holding the pedal (it doesnt seem to slowly sink) I think means I have a good master.

I bought one of those vacuum bleeders from harbor freight... I think that might have been a waste of money. Its nice that you can bleed without the pedal but I think the vacuum pulls in little air bubbles from the threads on the bleeders, which makes it pretty much impossible to see whether or not you are getting actual air bubbles from the lines or not. On the plus side, after about 4 cups worth of bleeding I have a very clean rear brake circuit... The fluid coming out looks brand new :flush:

Tomorrow AM I'll remove 2 clicks from each wheel cylinder and see if that helps.

I didnt buy the CCOT cylinders, got FC aftermarket ones from Cruiser Teq (at least I think they're OEM, they came in toyota/lexus packaging), although they might be the same as what CCOT sells. Looking at those photos @JohnnyC I'm surprised you can just take off the top like that... I may try topping off the wheel cylinder as a last-resort.

Time to do some forum homework.
 
RodrigzCrzr said:
best way to bleed is to purchase a brake bleeding unit one that you attach a hose and pump the bottle to 12psi. I had the same problem and this worked better cause it really ads pressure to the system and pushes the air out.
Click to expand...
Are you saying to pump fluid in from the bleeders towards the reservoir?
 
I love my Mighty Vac but I have to use Permatex Aviation type 2 B non hardening on the threads to get the bleeder threads to seal and not leak air in. PIA

Some folks folks really get violent on the pedal. push release a bunch time quickly. Press on the pedal, release quickly then press and hold pressure on the pedal; the bleed person opens the nipple a little, Pedal yells when the when the pedal nears the floor - bleeder person closes the bleeder. Rinse and repeat until no bubbles in fluid being bleed. Pedal person also keeps reservoir full.
Start at rear passenger, then driver rear, next front passenger and finally front driver.

Yea 5 clicks is too much 3 is better. Works better with wheel in place and torque down.
 
Curious on bleed order. On my truck the soft line from the chassis to the rear axle is on the passenger side, so the driver side rear is the furthest from the reservoir. Same for the front (driver side is further away in terms of brake line length). I might try the permatex as the vacuum bleeder is doing just like you say- pulling in outside air
 
procomsignathid said:
Are you saying to pump fluid in from the bleeders towards the reservoir?
Click to expand...
No, the Power Motive system pushes the fluid from master to bleeders. SOP is start (or start again in your case) from the furthest cylinder (pass rear). Pressurize master then go to the back and open bleeder.. watching for bubbles. Then work your way through progressively closer wheel cylinders. It goes fast! You can go through a lot of fluid so keep checking reservoir.

For the Landcruiser I use the Universal Round master adapter below (you pick when you buy, I also have a screw on one for German cars) I use their catch bottles cuz they came in my kit; but you can also just use what you have.

Once you use it, it would be hard to go back. It also makes it super fast to “change” brake fluid when it gets old n dark (usually with water molecules entrapped)
IMG_0246.webp

IMG_0245.webp
 
rlong said:
No, the Power Motive system pushes the fluid from master to bleeders. SOP is start (or start again in your case) from the furthest cylinder (pass rear). Pressurize master then go to the back and open bleeder.. watching for bubbles. Then work your way through progressively closer wheel cylinders. It goes fast! You can go through a lot of fluid so keep checking reservoir.

For the Landcruiser I use the Universal Round master adapter below (you pick when you buy, I also have a screw on one for German cars) I use their catch bottles cuz they came in my kit; but you can also just use what you have.

Once you use it, it would be hard to go back. It also makes it super fast to “change” brake fluid when it gets old n dark (usually with water molecules entrapped)
View attachment 4213570
View attachment 4213571
Click to expand...

The left rear brake plumbing is the furthest away from the master.
 
procomsignathid said:
Tomorrow AM I'll remove 2 clicks from each wheel cylinder and see if that helps.
Click to expand...
Just to double-check here; you do still have the residual valves for each brake line in the MC?
Maybe try this then; adjust your shoes all the way out (tight) so the wheels won't turn by hand, then try your pedal. How does that feel? Should be almost no play and super firm. This would be a good time to bleed too. If the pedal is solid with little play with engine on you can adjust the rear shoes loose enough to turn the wheels by hand. I always kept my drums adjusted kinda tight, where I could turn the wheel with one hand but they still dragged a bit. Maybe only 2 clicks... They'll self-clearance themselves soon enough.
 
Pighead said:
Just to double-check here; you do still have the residual valves for each brake line in the MC?
Maybe try this then; adjust your shoes all the way out (tight) so the wheels won't turn by hand, then try your pedal. How does that feel? Should be almost no play and super firm. This would be a good time to bleed too. If the pedal is solid with little play with engine on you can adjust the rear shoes loose enough to turn the wheels by hand. I always kept my drums adjusted kinda tight, where I could turn the wheel with one hand but they still dragged a bit. Maybe only 2 clicks... They'll self-clearance themselves soon enough.
Click to expand...

Not sure what you mean by residual valves in the master. I saw what looks like a dampening/proportioning valve on the rear circuit (bolts up to the booster), but I assumed it was just brake lines between the master and the wheel cylinders for the most part.

Work calls this AM and has denied me the time to work on the truck, so it will wait till this afternoon, but Im going to try the method you and some folks have suggested, namely cranking those adjusters as tight as possible, then bleeding from there.

Does anyone disagree with my assessment of the master cylinder? I can pick up that one from NAPA today as a fallback. Outside of seeing if the pedal moves to the floor after pressure is built, any other ways to see if the master is kaput?

I may also try clamping the soft line on the rear to see if that makes the problem go away... That would tell me if its air trapped in the wheel cylinders.
 
Ah sorry, shoulda searched that.

I'm not sure what the status is of the residual valve. After reading the article, my takeaway is that I need one for the rear drums, not for the front discs. Given that brakes were working prior to doing all this, my guess is that it's there. I'm not sure if they go bad / need to be serviced or not, or if what I did while servicing the rear brakes requires some maintenance there. When doing some searching on it, most of the threads concern what it is and when its needed (and should be removed for dics brake conversions).

My master cylinder does have ports that go out to the side (not the top), I noticed when looking for replacements they all have top-side ports. Given the history of this rig its possible its not the original MC on it (although it is forged with a TEQ stamp in it).
 
procomsignathid said:
any other ways to see if the master is kaput?
Click to expand...
Take it apart and look at it, is the bore scored, rusted or pitted? How's the rubber cups? Napa sells a little hone that fits just right. Put a rebuild kit in it while you're there. I rebuilt my MC a couple times before swapping in an 80 series MC.

20260622_161025.webp
 
If your master was working b4, I wouldn't mess with it. Most folks are successful by adjusting the cylinders to the max with the wheels on so the pistons don't move, then bleed. Once bled and no more air in the system readjust the shoes per FSM.
 
procomsignathid said:
Hello all-

I replaced my rear brakes this weekend, been running into an issue. Where I'm at now is that it takes a few pumps to build/hold pressure while the truck is off, Im not getting any air bubbles so it seems fine. But when I turn the truck on, pedal basically goes to the floor.

Here are the details I know:
  • 1978 FJ40 (mfr 10/77), with 2 wheel cylinders on each rear drum. discs up front.
  • Brakes were working prior to this weekend. Working in that the truck stopped just fine, but I noticed the rear reservoir was empty a week or so back and topped it off. Hadnt noticed a leak / drips since.
  • This weekend I replaced the following:
    • New wheel cylinders / pads / springs / drums on rear brakes, as well as soft line between chassis and rear axle
    • Front brakes untouched
    • Ensured that wheel cylinders were in the right place:
      • Left front (with the bleeder) adjustment wheel facing up, ramp angled back towards hub
      • Left rear (no bleeder), adjustment wheel facing down, ramp angled towards hub
      • RIght front (with bleeder, reverse thread adjuster), adjuster wheel facing up, ramp angled back towards hub
      • Right rear (no bleeder, reverse thread adjuster), adjuster facing down, ramp angled back towards hub
    • I adjusted all wheel cylinders:
      • made em as tight as I could (keeping them as even as I could eyeball it) while still getting the drum on
      • adjusted each cylinder wheel to tighten them further (with the tool, pulling away from the axle tightened on all four) until the drum wouldnt move
      • backed off 5 teeth
Since doing that work, I was worried that while bleeding I pushed the pedal too far down and the excess travel might have broken the master cylinder seal if there was any crud in there. So i plugged both front and rear outputs from the master cylinder (spare brake line, crimped), and with the engine on the pedal stayed put. So I think the master cylinder is fine.

Since doing that test, I have reconnected the front and rear lines, and bled all four corners repeatedly while my wife operates the brake pedal. Just as I said up top, pedal takes a few pumps to stiffen with the engine off, and with it on it sinks right to the floor.

Any help would be much appreciated!
Click to expand...
Did you bench bleed the master?
 
Progress!

I did what y'all suggested. Jacked up the rear of the truck again so the wheel were in the air, cranked down each wheel adjuster until each wheel wouldn't move (for each wheel i started with the rear cylinder, then once the wheel wouldn't move, I backed off a click, so I could adjust the forward cylinder to wheel stoppage, then set the rear one click tighter).

Bled the brakes again, although I will say not much in the way of air bubbles came out. This morning I backed off each adjuster three clicks, and now I have working brakes. It isn't done yet, they are still spongey, but the pedal no longer goes to the floor. After a few trips around the block I deemed it was safe to go into work.

I checked the drums with a infrared thermometer when I got there, was only light braking, and about 130 degrees at the perimeter. I think I can probably tighten one more click.

Still need to chase the remaining air pockets though. I havent bled the fronts again since tightening the rears, so I'll do that next, and maybe I just need to go through a couple bottles of fluid.
 
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