wheel cylinder installation

[amaurer]

having removed my wheel cylinders, how do i go about reinstalling them? I'm concerned that on the cylinder that has the piston upward will have a bubble of air trapped under the cup that cannot be bled (the air bubble would float up to the port in the inverted cylinder and bleed fine).

Do I need to fill the cylinder with fluid first, or some such? What about all the air in the lines, won't that just get trapped in there too while I'm bleeding?

 

[nuclearlemon]

what setup do you have? do you have the two cylinders on the sides? i've never had any issues with air being trapped

 

[amaurer]

yeah i've got front drums with two cylinders; one has the acting piston pointing down, the other points up.

my concern is that the underside of the cup is concave, and it seems to me that a bubble would happily rest there with nothing to force it downwards towards the exit port when bleeding.

 

[FF LC FREAK]

my concern is that the underside of the cup is concave, and it seems to me that a bubble would happily rest there with nothing to force it downwards towards the exit port when bleeding.

That is why you pump your brakes when bleeding. It will force the bubbles (since the pressure will force the air to mix with the brake fluid) out the bleeder valve. Use a clear tube on the bleeder to make sure you have all the air out of the cylinder.

Don't worry, people have been doing this since drum brakes were invented. Bleed until no more little air bubbles and you will be fine.

 

[etoddo]

x2 on the clear bleeder tube. Don't forget to bleed the master cyl as well. I went through 4 qts of fliud and still had soft brakes until I saw a thread on it here

 

[amaurer]

Don't worry, people have been doing this since drum brakes were invented. Bleed until no more little air bubbles and you will be fine.

ok ok, you win. engineer's curse, i tend to overthink things sometimes...

bleed master last, right?

 

[Pighead]

NO...bleed master first! "bench bleed" (or on the firewall) before attaching the brake lines.