Brake Bleeding Drama

[keybaud]

I am having a nightmare trying to bleed my brakes, so I'd be grateful for any advice on how to find the actual problem and/or resolve it.

I had the rear calipers refurbished and replaced all the brake hoses, as there was a leak in one of the calipers and the hoses were frayed in places. I bled the brakes manually, but even when no air came out, it still took 2 presses of the brake pedal before it went firm.

I then bought a Sealey pressurised brake bleeder and did the brakes again. The system stayed pressurised before I started bleeding, so there isn't a leak, and it really was a lot easier to bleed. With the pressurised container still attached, the brakes function correctly, but as soon as the pressure is released, it still needs to 2 pumps until firm.

The only thing I can  think of is that there may be an airlock in the brake bias valve. How can I test if this is the problem and how can I fix it? I've had the reservoir higher than the valve for a week and I tried bleeding the rear calipers with the 3-way junction above the bias valve.

[Jonathan Kay]

The system stayed pressurised before I started bleeding...

Was that with the cap that came with the Sealey kit and the added pressure from the kit still connected, and the loss of pressure needing two pumps with the usual cap and no added pressure?

Which way are your nipples pointing? Getting this wrong can create air traps. I imagine that could happen with a bias valve but I don't have any experience.

Jonathan

PS: I use a tube with a one-way valve from the nipple and a positive pressure system.

[Richard Price]

Are you using the original pads?

Sometimes it takes a while to get a decent pedal with new pads on worn discs.

[Ivaan]

What happens if you press down hard on the brake peddle and hold it for a while? Is it solid or does it sink slowly down?

Clive

[keybaud]

The problem was resolved by removing the calipers and bleeding them whilst vertical, with a piece of wood between the pads. This allowed the trapped air in the caliper to finally be removed. Two months of anguish over...

[Jonathan Kay]

Glad it's fixed.

Please could you describe the orientation or add a photo that might explain why that happened?

Thanks

Jonathan

[BlackSeven]

Presumably because for whatever reason the calipers aren't installed with the bleed nipples oriented as the caliper manufacturer intended; i.e. at the highest point.

Are you sure the calipers aren't handed and you installed left one on the right side and vice versa?

Rob

[elie boone]

Black seven, if you reverse the calipers you also reverse the connections.

[BlackSeven]

Exactly Ellie. I have no idea what caliper set-up is being discussed but some are handed and capable of being fitted on the "wrong" side which puts the bleed nipple too low.... result: impossible to bleed in-situ.

[Mankee]

As well as swinging the calipers up so that the bleed nipple is at the highest point, you can also gently tap the caliper body to coax pockets of air out. With the standard Sierra rear calipers, this is another reason to get rid of those horrible solid brake pipes attached to the sliding caliper; what were they thinking?

[keybaud]

The calipers are AP racing calipers and were installed correctly, which is horizontally; however, the entry and bleed point on the AP calipers are at equal levels. I jacked up the front of the car to raise the brake fluid reservoir above the height of the brake bias valve and this also raised the bleed nipple above the brake hose entry point. The reason for the air still being inside the caliper appears more to do with the fluid flow inside the caliper, hence the need to remove the caliper and hold it vertical to ensure all the air can be removed.

[Jonathan Kay]

Thanks

Jonathan