There's not much in a wheel cylinder that can be bad tbf. Unless the seals aren't fitted or the cylinder is cracked.
Sounds like you need to just pump it through a bit more.
Brake Problems - 76FJ40 Need Expert Advice.
- Thread starter chubot
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Sounds like you need to just pump it through a bit more.
pb4ugo
SILVER Star
FJ40 brakes are kicking my ass!!
Yesterday I replaced my front drum cylinders on my ‘71 FJ40. I used FC cylinders. Photo included. I can’t get pedal pressure on my brakes! It’s kicking my ass. I adjusted the drums to the point where the wheels wouldn’t turn and then backed off 3 clicks. I put Teflon tape on all 8 bleeder...
forum.ih8mud.com
Try a 2 man bleed - get someone to pump pressure up on pedal and hold it while you slacken the bleed screw with your clear hose attached and running into a container with a bit of fluid in it, do screw up as the pedal hits the floor. Repeat until no bubbles show in hose, vacuum bleeders are useful but as charliemeyer pointed out they suck air around the bleed nipple making it hard to work out what is going on.
45Dougal mentions the dash brake light senders - unplug them at the mc and run a test light from your battery and try each sender as your helper pumps up brake pressure, that will isolate which circuit builds pressure - light should go out as pressure builds.
45Dougal mentions the dash brake light senders - unplug them at the mc and run a test light from your battery and try each sender as your helper pumps up brake pressure, that will isolate which circuit builds pressure - light should go out as pressure builds.
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And if that doesn't work bleed both front and rear circuits at the same time - gravity bleed first, crack the nipple in each circuit furthest from the mc and let run into a jar, then pressure bleed as above but run around doing both circuits at once. That way you avoid a firm pedal in 1 circuit restricting a full pump in the other.
- Thread starter
- #25
Man I feel your pain. I just replaced the rr cylinders with the same CCOT I have on the LR. I’m getting solid fluid at both rear wheels and the right front caliper. But when I get to the left front caliper I’m getting a lot of air.
FJ40 brakes are kicking my ass!!
Yesterday I replaced my front drum cylinders on my ‘71 FJ40. I used FC cylinders. Photo included. I can’t get pedal pressure on my brakes! It’s kicking my ass. I adjusted the drums to the point where the wheels wouldn’t turn and then backed off 3 clicks. I put Teflon tape on all 8 bleeder...
I don't think the bleeder's are threaded properly anymore. I had to use a thick layer of Aviation Permatex B on all the Bleeder threads to get them to stop leaking air when using my Mighty Vac. They seal fine when closed but open to bleed they leak. 2 person pressure technique likely is fine with out the goop.
Air will slip in when the bleed screws are loosend. If you're getting a constant stream of small bubbles that's what is happening. It even happens with new cylinders and new bleed screws so I just ignore it. Air is not sneaking back up the lines.
If you're getting long burps of air or bubbles here and there then that's a concern and you'll need to do the two man technique. You can do it by yourself if you:
a) Tighten the bleed screw.
b) Jam a stick/flashlight/braunschweiger between the brake pedal and the front of your seat to depress the brake pedal and pressurize the line.
c) Quickly open and close the bleed screw to force out any entrained air.
d) Top up reservoir. Remove sausage.
e) Repeat starting with "b)".
If you're getting long burps of air or bubbles here and there then that's a concern and you'll need to do the two man technique. You can do it by yourself if you:
a) Tighten the bleed screw.
b) Jam a stick/flashlight/braunschweiger between the brake pedal and the front of your seat to depress the brake pedal and pressurize the line.
c) Quickly open and close the bleed screw to force out any entrained air.
d) Top up reservoir. Remove sausage.
e) Repeat starting with "b)".
- Thread starter
- #28
I just found a YouTube video where the guy was bleeding his brakes with the truck running. He found that air was entering in through the wheel cylinder piston. He replaced the wheel cylinder and solved his problem. I’ve replaced my wheel cylinder's and still no pedal. I haven’t had time this week to mess with it, maybe I’ll try the car running technique over the holiday weekend.
If there isn't any fluid leaking out of the wheel cylinders or fittings and you've got no pedal resistance then it's either excessive air in the lines (air doesn't compress well in a brake system) or fluid is bypassing the seals inside the master cylinder. If there's unexplained fluid loss then loosen the MC from the booster to make sure you're not squeezing fluid into the booster. If there's no leak out the back of the MC then you need to re-bleed the lines on both circuits or rebuild/exchange the MC.
pb4ugo
SILVER Star
To isolate if the problem is in the frt or the rear, you can use a pair of vise grips on the rear soft line. If the pedal gets better then you still have air in the rear. Carefully adjust the vise grips. You want to block the flow and not crush the line. If no change then test the frt.
You you could be sucking air at a connection or a bleeder.
You you could be sucking air at a connection or a bleeder.
pbgbottle
Forum Lifer
If you changed the master and let the fluid drain out of the lines at the wheels also. it will take longer than you think to pump all that air out of that far wheel. I just replaced some brake lines on my crusier and called my 40 year brake guy over to help me and he said get filling the reservoir and get pumping. It took forever to get the air out of the far wheel. I couldn’t believe how much fluid we pumped through it to get all the air out. It may just still be full of air. If you think all your new components are good. Tighten up the shoes to the drums too. Then bleed.
You can still bench bleed it in the truck. Make two small metal brake lines that loop back into the reservoirs and pump gently until no more bubbles appear in the reservoir
You can still bench bleed it in the truck. Make two small metal brake lines that loop back into the reservoirs and pump gently until no more bubbles appear in the reservoir
- Thread starter
- #32
I’ve been on vacation and haven’t posted in a while. I swapped out the synthetic brake fluid for some conventional and noticed a considerable difference in brake pedal. Is there any problem with using synthetic brake fluid in an old rig that any of you guys have noticed?
pb4ugo
SILVER Star
As i recall, most all brake fluids are synthetic, except for some British types.
I always use DOT3.
I always use DOT3.
- Thread starter
- #34
You’re right, I didn’t know that. I did notice that the brake fluid labeled as synthetic seemed a little thinner than the other. Either way, I need to get some more fluid and try to get more air out of the system. Maybe try the vice grips on the soft lines trick.
pb4ugo
SILVER Star
Hopefully it will help isolate where the air is.
Can also try setting your truck up as nose down as you can, either jack up the back or set up on steepest slope you can find. If there's a bubble sitting in the mc it can work its way back to the reservoir as you bleed, or just repeatedly apply brakes - fluid level will do a sudden drop.
I posted this on another thread. Replaced all hoses, front calipers, and rear wheel cylnders on my '77. Spent days bleeding in all different processes. Nothing worked, until this:
. . . . here is what got it done for me after (a) a power bleed with a Motive push pump bleeder 2x, and then (b) a two person old fashion pump and bleed (both with no success):
1. clamped the rear soft center hose -- had very firm pedal wtih no sinking, so the front calipers were good. (this isolates the air issues ot the rear)
2. filled the Motive pump bottle as full I could go without swamping the pressure gauge. Pumped it up to 15 lbs (above the 8-10 lbs on my first run).
3. cracked the Left Rear (driver side) bleeder, with a wrench tapped on the lines and the wheel cylinders mulitple times; pumped up the pressure to 15 again. Small bubbles coming out.
4. With the Motive in place, the bleeder attached to a hose into a catch can, pumped the brake pedal vigorously for 15 short pumps - 2x. Larger bubbles came out.
5. Ran a good quart of brake fluid through.
Done. Good pedal, no fade and stops nice and even. I am going to replace my drums (rear) as i know they are worn. Hopefully cut the brake pedel throw distance a bit. But the brakes work great.
This was a very frustrating experience and harder to bleed the air than any other car I have done. I think the relatively small reservoir for the rear wheel cylinders, that there are 4 wheels cylinders, and a large upward brake line run over the top of the pumpkin, results in not enough flow to push out the air. Simply, the short travel of the master cylinder plunger is not pushing enough brake fluid to expel the air in the line over the pumpkin. By putting a constant flow pressure and fluid movement with the Motive, combined with the repeated fast short pushes with pedal, it dislodged the air and that was it. The small flow of the rear reservoir also explains the sensitivity of the rear shoes settings, and why they have to be so tight. There is not much brake fluid push to expand all 4 rear wheel cylinders very far. . .
Mine has been great now for three months. Good luck!
. . . . here is what got it done for me after (a) a power bleed with a Motive push pump bleeder 2x, and then (b) a two person old fashion pump and bleed (both with no success):
1. clamped the rear soft center hose -- had very firm pedal wtih no sinking, so the front calipers were good. (this isolates the air issues ot the rear)
2. filled the Motive pump bottle as full I could go without swamping the pressure gauge. Pumped it up to 15 lbs (above the 8-10 lbs on my first run).
3. cracked the Left Rear (driver side) bleeder, with a wrench tapped on the lines and the wheel cylinders mulitple times; pumped up the pressure to 15 again. Small bubbles coming out.
4. With the Motive in place, the bleeder attached to a hose into a catch can, pumped the brake pedal vigorously for 15 short pumps - 2x. Larger bubbles came out.
5. Ran a good quart of brake fluid through.
Done. Good pedal, no fade and stops nice and even. I am going to replace my drums (rear) as i know they are worn. Hopefully cut the brake pedel throw distance a bit. But the brakes work great.
This was a very frustrating experience and harder to bleed the air than any other car I have done. I think the relatively small reservoir for the rear wheel cylinders, that there are 4 wheels cylinders, and a large upward brake line run over the top of the pumpkin, results in not enough flow to push out the air. Simply, the short travel of the master cylinder plunger is not pushing enough brake fluid to expel the air in the line over the pumpkin. By putting a constant flow pressure and fluid movement with the Motive, combined with the repeated fast short pushes with pedal, it dislodged the air and that was it. The small flow of the rear reservoir also explains the sensitivity of the rear shoes settings, and why they have to be so tight. There is not much brake fluid push to expand all 4 rear wheel cylinders very far. . .
Mine has been great now for three months. Good luck!
- Thread starter
- #38
Thanks TexLX450, I will try this. I just didn’t think it would be this difficult to get air out of the system.
- Thread starter
- #39
Ok, she stops but there’s a loud woosh of air coming from the booster and the pedal definitely goes down further than it used too. Could this mean my booster is bad? I made a video but not sure how to post it.
Well, not necessarily bad. Boosters do make some noise as they're using vacuum to lessen the required pedal force. Too much noise is bad though.
From an old SOR catalog...
To check your booster:
1. Engine off - press the brake pedal several times. Pedal travel should not change.
2. Start the engine and stop it after 1 or 2 minutes. Depress the brake pedal several times slowly. If the pedal goes down farthest the first time, but gradually rises after the second or third time the booster is air tight. (My note: You're using up the stored vacuum.)
3. With the engine stopped, press the pedal down several times. Start the engine while holding the pedal down. The pedal should move down a little and the pedal pressure should get softer.
4. Press the pedal all the way down (engine still running). Shut off engine. The pedal should not change position.
5. Restart the engine. Run for a minute or two and shut off engine. Press the brake pedal several times (this is a repeat of step 2). The pedal pressure should get harder/firmer each time you push on it.
If it doesn't work this way...
YOU"RE SCREWED!
From an old SOR catalog...
To check your booster:
1. Engine off - press the brake pedal several times. Pedal travel should not change.
2. Start the engine and stop it after 1 or 2 minutes. Depress the brake pedal several times slowly. If the pedal goes down farthest the first time, but gradually rises after the second or third time the booster is air tight. (My note: You're using up the stored vacuum.)
3. With the engine stopped, press the pedal down several times. Start the engine while holding the pedal down. The pedal should move down a little and the pedal pressure should get softer.
4. Press the pedal all the way down (engine still running). Shut off engine. The pedal should not change position.
5. Restart the engine. Run for a minute or two and shut off engine. Press the brake pedal several times (this is a repeat of step 2). The pedal pressure should get harder/firmer each time you push on it.
If it doesn't work this way...
YOU"RE SCREWED!
