Brake bleeding

avicenna110

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My grandfather had a brake shop and I wish I helped out more. I’m having issues bleeding my ‘65 with drums all around. I exchanged the master cylinder, the wheel cylinders, and shoes. I got all the air out, and adjusted the brakes and test drove the car a bit, it was fine but not great. I noticed the pedal was much higher than 9.6 inch per FSM. So I adjusted the pedal to the right height. The brakes became spongy, I thought probably because the rod isn’t pushing as far. But also I noticed there was a lot of bubble in the master cylinder when I pushed the pedal. Happens almost every time, not tiny bubbles but big ones. Sometimes the pedal gets hard after pressing, but then get spongy again. I tried bleeding the brake lines again for over an hour with my wife and there is no air in the lines. I know I’m supposed to bench bleed the master, which I skipped hoping I would eventually get all the air out, but let’s say there is air in the master, is it normal for the master cylinder to bubble so much when I’m not bleeding? It’s as if air is getting in from somewhere but I have checked everywhere and there is no leak. Help a guy make his grandpa proud 😊
 

middlecalf

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The MC is the highest point in the circuit, so when there’s fluid movement any air in the circuit will rise to the highest point (which can still be a local maximum). I’d bleed the MC insitu again and see if that helps.
 

avicenna110

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The MC is the highest point in the circuit, so when there’s fluid movement any air in the circuit will rise to the highest point (which can still be a local maximum). I’d bleed the MC insitu again and see if that helps.
I also noticed the nose of the car was jacked lower than the back ( I have all 4 wheels off) so it’s possible air got trapped in the back of MC? I now have the nose higher so I’ll try to bleed the MC on the car first.
 

middlecalf

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👍 It might burp out if you raise the nose for a bit.
 

avicenna110

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I “bench” bled the MC on the car and there was a lot of air in it, I pumped till all the air was out and no new bubbles could be seen.

I proceeded to bleed the lines, and spent a lot of time with no success. Since there is no leak and the MC was not giving bubbles during the bench bleed I must be bleeding the lines/cylinders wrong. I had originally tried a vacuum pump before all of this episode, and the bleeders couldn’t hold vacuum, air was getting sucked through the threads. So I resorted to the 2 person method, but I asked my wife to pump while bleeder was open because I had the end of the tube in the bottle submerged in fluid at all times, and the hose went above the lines on its way to the bottle. I didn’t think air would get in through the threads because I would see bubbles also coming out of the tubes with each pump, perhaps this is wrong?

I’ll do the conventional method tomorrow on all cylinders: hold down pedal, open bleeder, close bleeder, lift pedal, repeat. No more cute ideas and fancy pumps. Hopefully that’ll be the fix.
 

middlecalf

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And you‘re bleeding the furthest cylinders from the MC first, then moving toward the MC? Which on a ‘65 40 LHD with single circuit is the driver’s rear.
 

ceylonfj40nut

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Make sure you adjust the brake shoes at each manually using the brake adjuster in the drum until they stop the wheel from rotating. Then adjust two clicks back. Should drag a little. Do on all four tires. Bleed from furthest wheel to nearest wheel. Make sure bleed screws are located on top of the dust shield and not at the bottom (air will never leave if the bleed screw is at the bottom). Also make sure you use a tool to adjust the brake booster rod to the master cylinder. If the latter is off, rod hitting booster rod, out too much of a gap, no good.
 

avicenna110

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And you‘re bleeding the furthest cylinders from the MC first, then moving toward the MC? Which on a ‘65 40 LHD with single circuit is the driver’s rear.
yes starting with driver side in the back, then passenger side in the back, then front.

Make sure you adjust the brake shoes at each manually using the brake adjuster in the drum until they stop the wheel from rotating. Then adjust two clicks back. Should drag a little. Do on all four tires. Bleed from furthest wheel to nearest wheel. Make sure bleed screws are located on top of the dust shield and not at the bottom (air will never leave if the bleed screw is at the bottom). Also make sure you use a tool to adjust the brake booster rod to the master cylinder. If the latter is off, rod hitting booster rod, out too much of a gap, no good.
I did that last time after I bled it, but I should do it before bleeding? Isn’t the orientation of wheel cylinder fixed on the drum brakes? Like this:

1653746435726.png


And bleeding screw is attached to the back of the cylinders on each side of the dust cover, perhaps I’m not understanding it well.

On the 65 there isn’t a brake booster so one less complication.
 

sterling

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Make sure you adjust the brake shoes at each manually using the brake adjuster in the drum until they stop the wheel from rotating. Then adjust two clicks back. Should drag a little. Do on all four tires. Bleed from furthest wheel to nearest wheel. Make sure bleed screws are located on top of the dust shield and not at the bottom (air will never leave if the bleed screw is at the bottom). Also make sure you use a tool to adjust the brake booster rod to the master cylinder. If the latter is off, rod hitting booster rod, out too much of a gap, no good.
Excellent advice I went though what you are describing. And the parts replaced. Bled brakes over and over.
My solution was to do as described, but I adjusted the pads with more "drag" than I thought needed.

This seemed to firm up the brake pedal, and the pads "seated in".
Have also had new master cylinders have a bad seal and fail. I bought a replacement from Rockauto and they came in branded Aisen:clap: although not advertised as such.
My .02
 
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avicenna110

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Excellent advice I went though what you are describing. And the parts replaced. Bled brakes over and over.
My solution was to do as described, but I adjusted the pads with more "drag" than I thought needed.

This seemed to firm up the brake pedal, and the pads "seated in".
Have also has new master cylinders have a bad seal and fail. I bought a replacement from Rockauto and they came in branded Aisen:clap: although not advertised as such.
My .02

Ok got it, thanks I’ll adjust the shoes again before bleeding.
I’d appreciate if someone can shed light on bleeding screw being on the bottom of dust shield vs top. Perhaps it only applies to disc calipers?
 

sterling

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Disc bleeder location front 1979 FJ 40.
Rear drums bleeder below in the in middle of rear shield, at
197940 disc bleeder top.jpg
least on my year.
 

avicenna110

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Disc bleeder location front 1979 FJ 40.
Rear drums bleeder below in the in middle of rear shield, at View attachment 3019849least on my year.
Thanks, ok so only on disc caliper the bleeding screw could be on top or bottom, and it should be on top. I did this right on my 77 restoration but I’m no where near bleeding that one. On the ‘65 (for this post) I have drum brake on all 4 wheels and the wheel cylinders are installed per diagram above.
 

sterling

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Rear bleeder on a 79 fj40.
I bled the hell out of mine to be honest, helps to have another person. "Down ok hold" for the other person.
rear bleeder 1979 40.jpg
Bleed more than you would think to.
Or a one man bleeder kit.
 

sterling

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Thanks, ok so only on disc caliper the bleeding screw could be on top or bottom, and it should be on top. I did this right on my 77 restoration but I’m no where near bleeding that one. On the ‘65 (for this post) I have drum brake on all 4 wheels and the wheel cylinders are installed per diagram above.
Disc brake bleeder screw for top. Drums get the middle/bottom.
Take a step back for a minute and go back.

Only for a 1979 40, my info.
I always remind myself, these are stupid awesome vehicles.....ain't that hard...don't overthink.
 
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avicenna110

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Update: adjusted the shoes before bleeding again, they were way way off. Now I’m gonna attempt to bleed.

In terms of getting the air out of the lines and system, isn’t it better if the shoes are not in contacts with the drum? That way they travel more and push the air out. What is the intuition behind adjusting shoes/cylinder before bleeding? I understand that if the shoes are close to the drums they are required to travel less so therefore more effective brakes, but I still haven’t understood the logic behind doing it before bleeding. Doesn’t mean I don’t listen to you guys though.
 

avicenna110

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Disc brake bleeder screw for top. Drums get the middle/bottom.
Take a step back for a minute and go back.

Only for a 1979 40, my info.
I always remind myself, these are stupid awesome vehicles.....ain't that hard...don't overthink.
This is my 65 front drums, there is one on the other side of each

EF1AAF8C-0B98-4A0D-A194-00A4D35309DE.jpeg


85D8974C-04B2-4477-818E-8A7A6D56C5D5.jpeg
 

sterling

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