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Author: Subject: Drum brake bleeding
budha

posted on 22/6/21 at 08:14 PM Reply With Quote
Drum brake bleeding

These damn drum brakes...

Had to change the rear brake cylinders and now the bleeding makes me crazy. It simply does not work. I do not get any bubbles but the brake pedal is still soft and can be pushed till the end. Master cylinder is fine I checked that.

I have an English axle with only one bleeding screw on the left side.

Any tricks how to get this to work?

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Mr Whippy

posted on 22/6/21 at 08:45 PM Reply With Quote
Easy bleed kit will sort it out. I had a similar issue with the old landrovers brakes due to the loops of pipe and was sorted in seconds with the easy bleed. Autosave had a similar but better quality one which I bought later.

Oh yeah and with drums it's better to wind out the adjusters till the shoes are tight or put the hand brake on. Otherwise the pressure from pumping the breaks does nothing more than move the shoes with little flow out the bleed screw.

[Edited on 22/6/21 by Mr Whippy]

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adithorp

posted on 22/6/21 at 09:08 PM Reply With Quote
Because the cylinders sit at a slight angle they can hold a bit of air behind the higher piston. Bleed with the adjusters fully off and adjust after to reduce that.





"A witty saying proves nothing" Voltaire

http://jpsc.org.uk/forum/

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steve m

posted on 22/6/21 at 10:01 PM Reply With Quote
"I have an English axle with only one bleeding screw on the left side."

Ive been down this route, and its painfull, in the end i went for bleed nipples on all wheels, and just a T feed to both rear wheels

The only ways to successfully bleed your setup is by vacuum or pressure feeding the rear, or the way i did it, was to raise the RHS of the car up about 24" so that the highest point on the RHS is higher than any brake lines etc, and bleed the system

A lot of the problem is the brake pipe that goes over the back axle collects air, and thats why you need to jack up so high, you could try making it more level





Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at




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steve m

posted on 22/6/21 at 10:06 PM Reply With Quote
something said above, also comes to mind,

Take all the brakes apart as in shoes springs etc, and stick a big G cramp over all four pistons, two each side, and bleed the system,

No movement in the pistons, but all air displaced





Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at




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adithorp

posted on 23/6/21 at 08:36 AM Reply With Quote
quote:
Originally posted by steve m
"I have an English axle with only one bleeding screw on the left side."...

...The only ways to successfully bleed your setup is by vacuum or pressure feeding the rear...

...A lot of the problem is the brake pipe that goes over the back axle collects air, and thats why you need to jack up so high, you could try making it more level


As there were thousands of cars on the road lond before ezibleeds were available, those first 2 points clearly can't be true.
There are still thousands of cars with sections of brake pipe that loop upward so again jacking like that is not required.

A standard careful and methodical 2 man bleed is all that's needed. Done right any air bubbles will not return up any loops fast enough to be a problem due to the small pipe diameter before the next push.





"A witty saying proves nothing" Voltaire

http://jpsc.org.uk/forum/

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Mr Whippy

posted on 23/6/21 at 09:10 AM Reply With Quote
quote:
Originally posted by adithorp
quote:
Originally posted by steve m
"I have an English axle with only one bleeding screw on the left side."...

...The only ways to successfully bleed your setup is by vacuum or pressure feeding the rear...

...A lot of the problem is the brake pipe that goes over the back axle collects air, and thats why you need to jack up so high, you could try making it more level


As there were thousands of cars on the road lond before ezibleeds were available, those first 2 points clearly can't be true.
There are still thousands of cars with sections of brake pipe that loop upward so again jacking like that is not required.

A standard careful and methodical 2 man bleed is all that's needed. Done right any air bubbles will not return up any loops fast enough to be a problem due to the small pipe diameter before the next push.


I have workshop manuals from the 1950's clearly showing gravity feeding brakes as standard procedure in garages, it's certainly nothing new and definitely more effective than pressing the pedal.

One tip to make life a lot easier on yourself when working on brakes is to put some cling film under the reservoir cap and screw it back on as there is a small vent hole in it. That way when you take a caliper off etc very little if anything drains out of the pipes and bleeding it after takes just a few seconds just using the pedal to clear just the air in the caliper.

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budha

posted on 23/6/21 at 07:59 PM Reply With Quote
Thanks for all your answers. Seems I am not the only one struggling with the drum brakes.
I have an air compressor here so I will build a tool to pressurize the system.

quote:
Originally posted by adithorp
Done right any air bubbles will not return up any loops fast enough to be a problem due to the small pipe diameter before the next push.


Well I guess that is the questions than....what is the right way?

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David Jenkins

posted on 23/6/21 at 08:13 PM Reply With Quote
quote:
Originally posted by budha
Thanks for all your answers. Seems I am not the only one struggling with the drum brakes.
I have an air compressor here so I will build a tool to pressurize the system.

quote:


You don't need much pressure - my Ezibleed connects to a car tyre at 18psi (max is 20psi).





The older I get, the better I was...

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budha

posted on 25/6/21 at 08:12 PM Reply With Quote
I managed to get some air out with pressure bleeding. Now the pedal feels pretty solid. Thanks guys!

Funny story:
I 3d printed a cap with 1/8 thread to connect it to my air compressor. Unfortunately the print was not solid enough, so I ended up with a burst cap and brake fluid all over the place... (max 20PSI....) Luckily that was after initial success. I will print another one. This time with 100% fill rate.

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gremlin1234

posted on 25/6/21 at 08:38 PM Reply With Quote
quote:
Originally posted by budha
I managed to get some air out with pressure bleeding. Now the pedal feels pretty solid. Thanks guys!

Funny story:
I 3d printed a cap with 1/8 thread to connect it to my air compressor. Unfortunately the print was not solid enough, so I ended up with a burst cap and brake fluid all over the place... (max 20PSI....) Luckily that was after initial success. I will print another one. This time with 100% fill rate.
you only want about 2-4 psi, absolute max 5, else yes you spray brake fluid over the entire engine bay
the original Gunstan kits did this.


[Edited on 25/6/21 by gremlin1234]

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JeffHs

posted on 26/6/21 at 09:29 AM Reply With Quote
A single handed method I've used successfully is to attach a very long pipe to the bleed nipple and hang it up on the garage roof. Open the nipple and pedal fluid into the pipe until there is clear bubble free fluid above the level of the master cylinder. tighten bleed nipple, pinch pipe and drain into a can.
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Mr Whippy

posted on 26/6/21 at 09:38 AM Reply With Quote
quote:
Originally posted by JeffHs
A single handed method I've used successfully is to attach a very long pipe to the bleed nipple and hang it up on the garage roof. Open the nipple and pedal fluid into the pipe until there is clear bubble free fluid above the level of the master cylinder. tighten bleed nipple, pinch pipe and drain into a can.


Yeah I have seen this in manuals, looks very straightforward.

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