- Thread starter
- #41
I agree! It looks like it should be angled and one of the reasons I questioned if this MC was the root of my problems.
1973 brake issues (1 Viewer)
- Thread starter WyoMike
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
- Thread starter
- #42
Status update: started from scratch. Pulled MC to verify pushrod to MC was correct, it was. Bench bled the MC. Purchased a Mityvac and proceeded to bleed all wheels using Mityvac’s recommendation of starting closet wheel to MC first to furthest. Had really good pedal pressure though I still needed to press about a 1/3 down before pressure. Two pumps and rock solid. Knew I still had air in there and decided to try furthest away first, driver’s side rear. Here’s where I made a first bad call: I decide to use the vac and pedal press together. Pedal went all the way to the floor after two wheels with no pressure. Went back to using just the vac and started drivers rear and went all the way around. Turned out worse! Then I decided to start at the front and work back. By the second wheel yours truly let the MC run try!! Second bad move of the day.
Back to square one. Bench bled the MC in place. Started drivers font and worked around to and finished at the drivers rear. I used the Mityvac and pulled a large volume of fluid through each wheel cylinder just to be sure.
Success! Though I still have to partially press the pedal before pressure. Seconded pump is rock solid. So I still have a little air in there somewhere but now feel confident I can drive it up on the trailer to go get exhaust installed Thursday. Just seems wrong to start closest and finish furtherest away!
Going to take a break (no pun intended) and try again tomorrow. Thinking of starting furthest away. If I screw up I know I can start over from scratch once again. What a major PITA!
Back to square one. Bench bled the MC in place. Started drivers font and worked around to and finished at the drivers rear. I used the Mityvac and pulled a large volume of fluid through each wheel cylinder just to be sure.
Success! Though I still have to partially press the pedal before pressure. Seconded pump is rock solid. So I still have a little air in there somewhere but now feel confident I can drive it up on the trailer to go get exhaust installed Thursday. Just seems wrong to start closest and finish furtherest away!
Going to take a break (no pun intended) and try again tomorrow. Thinking of starting furthest away. If I screw up I know I can start over from scratch once again. What a major PITA!
pb4ugo
SILVER Star
I would use a pair of vise grips and carefully adjust them and clamp the rear hose. If the pedal becomes good, then the air is in the rear. If no change then move the clamp to the frt, if it's better then the frt has air. You want to stop the flow with the V/G and not crush the hose.
I don't run drums, but have read tons of posts on bleeding drums. This subject is very redundant. It seems folks that have the best results is to put the wheels on, adjust the adjuster to the max so the wheel doesn't spin. This stops the w/c's pistons from moving. Then folks bleed. Afterwards they properly adjust the brakes.
I don't run drums, but have read tons of posts on bleeding drums. This subject is very redundant. It seems folks that have the best results is to put the wheels on, adjust the adjuster to the max so the wheel doesn't spin. This stops the w/c's pistons from moving. Then folks bleed. Afterwards they properly adjust the brakes.
I think you have to adjust your shoes tighter
- Thread starter
- #45
Darn, I forgot to to max out the shoes!!! Did that yesterday but forgot today! Thanks.
- Thread starter
- #46
Tomorrow I will try bleeding the brakes again after I max out the shoes. Then I won’t back them off as much as they are now! Good idea thanks.
Skreddy
SILVER Star
There’s also the pushrod from the pedal to booster that could be a little loose if it takes some pedal swing before engaging. But tightening the drums may be your cure.
- Thread starter
- #48
I did find the lock nut was loose on the pedal rod to booster and tighten it back up today with no change. I agree with everyone the shoes need to be adjusted. Will try that tomorrow. Thanks!
This is experience with my 1973 FJ40 with Aisin MC, rebuilt booster, and aftermarket brake cylinders properly positioned (note: four different cylinders for the rear axle, two x two different cylinders for the front.)
To bleed these brakes, my experience has been that you need to adjust both brake cylinders in each wheel TIGHTLY against the drum before bleeding.
I've always been successful with the two person (
) bleeding method, the wife on the pedal and me under the truck on the bleed screw.
If the wheel cylinders move at all when you pump the pedal, it doesn't contract the air bubbles effectively, letting them stay behind. With both shoes up against the drums, the wheel cylinders can't move, so they don't take up any of the pumping pressure, and the full hydraulic force squeezes the bubbles. Tiny bubbles have no choice but to "go with the flow." That's my theory, and it's worked for me since 1977.
I have wifey stand on the pedal, and I crack the bleeder to let fluid flow through a clear tube into a jar, but close the bleed screw well before the stream of fluid peters out. I start from the furthest cylinder from the MC, driver's rear, then passenger rear then passenger front then driver front. Bleed screws don't seal on the threads like pipe threads, so teflon tape isn't called for.
Once completed, I back off the adjusters until the wheel spins freely with a little rub from the shoes, once again pushing hard on the pedal between spins in order to re-center the brake shoes.
Good luck with that funky MC. My Aisin that looks the same as your picture in post #1 (still available from @cruiseroutfit as far as I know) didn't need a bench bleed.
I open the bleed screws on the one of the cylinders in both the front and rear brakes, waited for the reservoirs to start going down, then close the screws and start pumping and working the bleed screw.
To bleed these brakes, my experience has been that you need to adjust both brake cylinders in each wheel TIGHTLY against the drum before bleeding.
I've always been successful with the two person (
) bleeding method, the wife on the pedal and me under the truck on the bleed screw.If the wheel cylinders move at all when you pump the pedal, it doesn't contract the air bubbles effectively, letting them stay behind. With both shoes up against the drums, the wheel cylinders can't move, so they don't take up any of the pumping pressure, and the full hydraulic force squeezes the bubbles. Tiny bubbles have no choice but to "go with the flow." That's my theory, and it's worked for me since 1977.
I have wifey stand on the pedal, and I crack the bleeder to let fluid flow through a clear tube into a jar, but close the bleed screw well before the stream of fluid peters out. I start from the furthest cylinder from the MC, driver's rear, then passenger rear then passenger front then driver front. Bleed screws don't seal on the threads like pipe threads, so teflon tape isn't called for.
Once completed, I back off the adjusters until the wheel spins freely with a little rub from the shoes, once again pushing hard on the pedal between spins in order to re-center the brake shoes.
Good luck with that funky MC. My Aisin that looks the same as your picture in post #1 (still available from @cruiseroutfit as far as I know) didn't need a bench bleed.
I open the bleed screws on the one of the cylinders in both the front and rear brakes, waited for the reservoirs to start going down, then close the screws and start pumping and working the bleed screw.
Skreddy
SILVER Star
- Thread starter
- #51
Hey thanks for the info! Maybe there is light at the end of the tunnel after all!This is experience with my 1973 FJ40 with Aisin MC, rebuilt booster, and aftermarket brake cylinders properly positioned (note: four different cylinders for the rear axle, two x two different cylinders for the front.)
To bleed these brakes, my experience has been that you need to adjust both brake cylinders in each wheel TIGHTLY against the drum before bleeding.
I've always been successful with the two person (
If the wheel cylinders move at all when you pump the pedal, it doesn't contract the air bubbles effectively, letting them stay behind. With both shoes up against the drums, the wheel cylinders can't move, so they don't take up any of the pumping pressure, and the full hydraulic force squeezes the bubbles. Tiny bubbles have no choice but to "go with the flow." That's my theory, and it's worked for me since 1977.
I have wifey stand on the pedal, and I crack the bleeder to let fluid flow through a clear tube into a jar, but close the bleed screw well before the stream of fluid peters out. I start from the furthest cylinder from the MC, driver's rear, then passenger rear then passenger front then driver front. Bleed screws don't seal on the threads like pipe threads, so teflon tape isn't called for.
Once completed, I back off the adjusters until the wheel spins freely with a little rub from the shoes, once again pushing hard on the pedal between spins in order to re-center the brake shoes.
Good luck with that funky MC. My Aisin that looks the same as your picture in post #1 (still available from @cruiseroutfit as far as I know) didn't need a bench bleed.
I open the bleed screws on the one of the cylinders in both the front and rear brakes, waited for the reservoirs to start going down, then close the screws and start pumping and working the bleed screw.
- Thread starter
- #52
Good to know! Thanks
Conforming with the repair manual, I don't tighten the shoes all the way to the drums for bleeding. When the bleeder screw is open sufficiently (1/2-turn is described in the manual), pressurized fluid exists the cylinder, thru the bleeder and vinyl tube. The return springs on the shoes are pushing back on the pistons enough to allow bubbly hydraulic fluid to escape the system. With a slight hack, I'm relying on an air and DOT3-tight connection up to a point when the clear vinyl tube goes from pointing up from the bleeder nipple to its arc downward into the catch bottle, because I'm bleeding the system solo and don't close the bleeders when the pressure is down, during brake pedal retreat. It is basically a gravity-bleed, with moments of pressure from the master cylinder to push bubbles against gravity and out of the system.
It is a big project adjusting the amount of drag on the eight shoes. But, it helps having a lift, or the wheel removed, and the drum retaining screw is on and tight. It is a bit confusing too, as looking from the top, (for tightening) the wheel cylinder either adjusts clockwise, or counterclockwise. And then you need to figure out that rotation (cantilever action, or just pushing) for using the brake spoon, or screwdriver, in between trips back into the cab for re-centering the shoes by depressing the brake pedal. Recently, I've made (partly complete) notes, so I can find the cylinder adjuster nuts behind the wheel backing plugs, and the direction necessary for tightening, incomplete info pertaining to the rear axle.
It is a big project adjusting the amount of drag on the eight shoes. But, it helps having a lift, or the wheel removed, and the drum retaining screw is on and tight. It is a bit confusing too, as looking from the top, (for tightening) the wheel cylinder either adjusts clockwise, or counterclockwise. And then you need to figure out that rotation (cantilever action, or just pushing) for using the brake spoon, or screwdriver, in between trips back into the cab for re-centering the shoes by depressing the brake pedal. Recently, I've made (partly complete) notes, so I can find the cylinder adjuster nuts behind the wheel backing plugs, and the direction necessary for tightening, incomplete info pertaining to the rear axle.
pb4ugo
SILVER Star
Its been 30 yrs or more since having drum brakes or looked at this adjustment procedure, but I think the manual states the end of the adjuster handle is to move away from the axle to expand the shoes. I also seem to recall proper adjustment has no drag or resistance when spinning the tire. I thought you are to adjust till the tire doesn't spin then back off the adjuster something like 3 or 5 notches, then proceed to the other shoe. It's the only way to know each shoe is adjusted evenly, because there are 2 adjuster at each drum. As bleeding goes, do what works for you. I found disc brakes work and are pretty much maintenance free.
- Thread starter
- #55
