Brake bleeding, bleeding brake bleeding!

[richard at home]

I am struggling to get any pedal feel back after changing rear calipers. No leaks and using a Easi-bleed, no air coming out either.

Are Easi-bleed's just cr@p?

My master cylinder has a tiny reservoir (like an eggcup full), so if I get someone to pump the brake pedal for me, can I keep the easi-bleed attached to keep it topped up so that I'm not running back and forth checking the level?

Just to make things more interesting, the car also has a remote servo which doesn't look like it's got enough tilt on it. I guess I can allow any trapped air in it, to get out if I loosen the output pipe nut?

It's a bit odd as I have bled the brakes on this car before without any issues but this time there defo some air in there somewhere that just doesn't want to come out...

[steveo3002]

you can pump the pedal with it attached...personnaly i wouldnt floor it as on older ones it can flip the seal inside

what pressure are you using ...i tend to go towards the high side of the recommended setting

[sunbeam alpine]

What I've done sometimes with difficult cars is "reverse bleed". I have a small pump bottle (like a soap dispenser) with a length of plastic pipe on it which contains approximately half a liter of brake fluid. I attach the pipe to the bleed nipple on the caliper and pump the liquid back up the system.

[stevieturbo]

richard at home said:

I am struggling to get any pedal feel back after changing rear calipers. No leaks and using a Easi-bleed, no air coming out either.

Are Easi-bleed's just cr@p?

My master cylinder has a tiny reservoir (like an eggcup full), so if I get someone to pump the brake pedal for me, can I keep the easi-bleed attached to keep it topped up so that I'm not running back and forth checking the level?

Just to make things more interesting, the car also has a remote servo which doesn't look like it's got enough tilt on it. I guess I can allow any trapped air in it, to get out if I loosen the output pipe nut?

It's a bit odd as I have bled the brakes on this car before without any issues but this time there defo some air in there somewhere that just doesn't want to come out...

Did you let the system run dry or something ?

What car ?

In reality, simply opening the nipple and letting gravity do the work usually gets you a good start. Or a cheap syringe and clear tube will let you pull or push fluid as needed.

[paintman]

richard at home said:

Are Easi-bleed's just cr@p?

Used one for years on various cars and never had a problem.

[GreenV8S]

How much of the system drained while you were working on the calipers? Usually you'd aim to keep fluid loss to a minimum but if you've let the system drain then you could have air in a bias valve, ABS controller or similar places that can be hard to bleed.

I'd expect to find that any modern car had calipers arranged to bleed easily, but take a look at the arrangement on yours to see whether air will find its way to the bleed nipple easily. I've seen a few cars where air could get trapped because the link pipe was positioned incorrectly or the bleed nipple was fitted to the bottom instead of the top. If your brakes aren't totally standard, give the caliper plumbing a sanity check.

[Tlandcruiser]

Did you reassemble the brakes correctly and are any sliders seized?

[richard at home]

Tlandcruiser said:

Did you reassemble the brakes correctly and are any sliders seized?

Brakes assembled fine without any issues. The pistons are tightening the pads ok.

The car is a custom, the brakes are Jag IRS girling. There's a remote servo mounted just above the rear axle.

While the axle was out and I was servicing the brakes, I did try and keep fluid loss to a minimum.

It's possible I let the reservoir drop too low while bleeding initially (without the easi-bleed) as its tiny.

Another possible issue is that the servo isn't mounted at an angle and its at the highest point in the system, especially as the car is jacked way up at the back now. So given that I suspect the air is all in there!

It's in a really awkward location and I can only reach it from underneath. I can't see any dedicated bleed nipple for the servo, but I have loosened the output pipe until I saw fluid come out.

It may be worth firing up the motor to get some vaccuum in the servo to see if it will dislodge any air bubbles...

[ninjag]

I used this for brake bleeding and it's pretty awesome. You spend a little more in brake fluid but it's so easy to not only bleed but also swap the whole fluid out.

https://www.amazon.co.uk/gp/product/B081HD3CNB/ref...

Might be similar in stock.

[GreenV8S]

Given the unusual custom setup you describe I suggest you look carefully at the orientation and routing of the brake lines to make sure that every chamber in the hydraulic system has a path for air to get out from the highest point. This means the brake master, and any bias valve, and each cylinder of each caliper. If there are any dead spaces where air could collect, you'll need to figure out how to get the air out. Brake fluid is viscous enough, and brake lines are small enough, that it's usually no problem chasing air out of brake lines even if it means pushing the air 'downhill', but that doesn't work where there are any bigger chambers.

[richard at home]

Oh and just to add to the mix, there's a hydraulic handbrake!

Further investigation revealed that one piston on the rear caliper (which I rebuilt) is retracting back into the caliper when you take pressure off the pedal. This in turn means it has a long way to go before the pedal pressure comes up, so it feels like it's still got air in.

I have just taken the caliper off the car again to check it.

Here's a video of the piston.

https://youtu.be/xISZ7GsJKBM