Air in the Brake Lines

[BEAR-AvHistory]

Power bled it a few times no air coming out of calipers. Pedal is soft, stops too long. Can the master cylinders be bled while in the car?

[compuatic]

Yes if your master cylinder has a bleed screw on it. many of them do. other than that I suggest manual bleeding w/two people. the power bleeders can be hit and miss.

[BEAR-AvHistory]

Yes if your master cylinder has a bleed screw on it. many of them do. other than that I suggest manual bleeding w/two people. the power bleeders can be hit and miss.

Masters are dual Wilwood. Will take a look for bleed screw.

[scrubs]

I started with this (https://www.amazon.com/dp/B09PYBGVSQ?psc=1&ref=ppx_yo2ov_dt_b_product_details) to get the masters going and get most of the lines with fluid in them ( I am running separate front/rear reservoirs). Then switched to the good ol' 2 person. There were times I thought I was there...and wasn't. Kept checking the flares and eventually got there.

I recommend once you've "pressure tested" things that you pump on that pedal a bunch, let it sit over night, then check all fittings. I did that thinking I was good and found a droplet on a panel. Tightened things up and re-tested. I found a weak area to be those damn plastic caps on the MC inlets. You need to crank on those damn clamps.

[D Stand]

I couldn’t get the air out power bleeding either. Wilwood has some good videos of the proper way to bleed their dual masters. You need 3 people. 1 at the pedal, 1 at front right and 1 at rear right. Open both bleeders at the same time while keeping pedal pressed. Repeat on other side as well. Sounds weird but it worked first time for me.

[CraigS]

D thanks for bringing that up. Often the balance bar can not provide enough angle if you blead just a front or just a rear. The MC that is not being bled and the balance bar will not allow the MC being bled to move it's full travel. So the MC you are bleeding only goes maybe 3/4 travel and bubbles can stay in that 1/4 travel space that is never bled. Bear, you probably already know this but if you get an extra person they may be new to the procedure. One key is that they never do anything that you haven't told them. Especially guard against a bleeder still being open when the brake pedal is released.

[RoadRacer]

I’ve always bled both ways, but backwards gives best results in the 33. Ie push fluid in the caliper - it bleeds the mc that way.

[runamuk]

Did you bench bleed the master cylinders?

I hooked up lines from both of my master cylinders and then ran them to the reservoir and just dropped them down into the fluid, then pumped the brake pedal until air bubbles stopped appearing. Then I reconnected the brake lines to the master cylinders and bled the brake lines.

[BEAR-AvHistory]

Did you bench bleed the master cylinders?

I hooked up lines from both of my master cylinders and then ran them to the reservoir and just dropped them down into the fluid, then pumped the brake pedal until air bubbles stopped appearing. Then I reconnected the brake lines to the master cylinders and bled the brake lines.

The car has been in use since 2015 with sub 100ft stops. have done a number of pad changes in the past without causing a problem. This time did a 4 wheel caliper replacement when this issue popped up. Can't bench bleed the masters as they are in the car & would be a major adventure to try to get them out. Was reading the suggestions the guys posted & found this today on a FFE chassis with dual masters.

Looks messy but might work. Otherwise will have to search out fittings to bleed back into the revivors as you have done. Have plenty of tubing so that would not be a problem


https://thefactoryfiveforum.com/forumdisplay.php?2-Roadster&styleid=1

[runamuk]

The car has been in use since 2015 with sub 100ft stops. have done a number of pad changes in the past without causing a problem. This time did a 4 wheel caliper replacement when this issue popped up. Can't bench bleed the masters as they are in the car & would be a major adventure to try to get them out. Was reading the suggestions the guys posted & found this today on a FFE chassis with dual masters.

Looks messy but might work. Otherwise will have to search out fittings to bleed back into the revivors as you have done. Have plenty of tubing so that would not be a problem


https://thefactoryfiveforum.com/forumdisplay.php?2-Roadster&styleid=1

Sorry, I didn't realize your car had been on the road for a while. It sounds like you have a caliper or two that just needs a little more bleeding.

BTW, I "bench" bled my master cylinders installed in the car, I did not remove them.

[BEAR-AvHistory]

Sorry, I didn't realize your car had been on the road for a while. It sounds like you have a caliper or two that just needs a little more bleeding.

BTW, I "bench" bled my master cylinders installed in the car, I did not remove them.

No problem. Just posted that so any suggestions that might be posted would realize the history of the system. Have run almost a gallon through the calipers with a power bleeder thats why I think it maybe the master cylinders. My son in law will be over on Saturday so we can try some two person stuff to see if we can clear the air out. That's why I was looking for suggestions. I know myself & a number of others have had problems bleeding the Wilwood units.

The bleeders on the calipers seem to be good as there is no leakage of air back into the calipers from them that I can detect. If I run the power bleeder then no bubbles come out. Also the brake fluid coming out of the bleeders changed from dirty to clear early on. The bleeders are also dry after sitting for a few days.

That said will run through all the connection points to insure they are air tight.

[Fixit]

If I run the power bleeder then no bubbles come out.

My best guess is you've got a high spot (in a chamber/void of some sorts) in the brake system. If there is a "chamber/air dome" in a MC or Caliper the power bleeder will just compress the air, and shove the fluid right on by. Remove the fluid pressure, the air expands and mushy pedal.

Bench bleeding in the car may not have been ideal. "True" bench bleeding gives you the opportunity to have the MC tilted at a (sometimes severe) angle to ensure the reservoir inlet and pressure outlet are "up" enough for air to be pushed out of the cylinder, and clean fluid sucked back in.
Also, a key element of the procedure is "slow & steady wins the race". Very slow compression & very slow release of the MC piston. (You want to push the air out with the fluid, not trap & compress it.

[Jim S]

I too had problem getting all the the air out of the lines in my build. A few things that I did that helped that I didn't see posted here and would apply equally to your situation with new calipers:

1) I have the IRS rear with Mustang GT brakes. The FFR mounting brackets position the rear calipers so they are almost parallel to the ground. This doesn't position the caliper bleeder screw in a good position. I removed the forward mount bolt and tipped the entire caliper back so it was nearly vertical. Getting the bleeder screw positioned at the highest point made a big difference. You need to put something between the brake pads if you are going to bleed by pumping the brake pedal. I had my calipers tipped back far enough that the rotor was no longer sandwiched by the brake pads.

2) Use a dead blow hammer to tap the calipers. Surface tension in the brake fluid can trap the air bubbles inside the caliper and not allow them to travel to the bleeder screw.

3) If you make use of a hose and catch bottle partially filled with brake fluid attached to each bleeder screw such that no air is sucked back in when the pedal is released, you can rapidly pump the brake pedal using short strokes. This method will help break up surface tension in the MC and the brake lines themselves allowing the air to move to the calipers.

The Wilwood method (link in one of the previous posts) is a good idea when bleeding a system with dual MCs. You can do it by yourself if you use a hose / catch bottle on each wheel cylinder right side / left side pair. Just make sure You start off with the hose covered by brake fluid in the catch bottle so no air is sucked back into the caliper when you release the brake pedal.

I hope this ideas help you out.

Jim

[BEAR-AvHistory]

Going to try a longshot. Can't get a wrench onto the outlet ports of the master cylinders. That said I do have two unions both not far from the master cylinders. Intend to use my catch bottles at the unions. Will use the dead blow hammer on the master cylinders with a piece of hard wood as the striking face. If I can clear the masters will do the calipers again to remove any air I might let in opening the brake lines.

[BEAR-AvHistory]

Long shot raised the pedal & can lock front wheels as compared to a long stop. Son in law helped as chief pedal pusher. Will let it sit for a day, started to rain, do it one more time. After that will do each wheel to be sure I have not let any air in below where I opened the pipes. Last step will be to set the balance bar. Hope to be done this week.

Thanks all for the input.:D