Bleeding Wilwood brakes

[Rian_Colorado]

I really thought I was done with this part, but alas......

So I'll start from the beginning. Several months ago, finally got my calipers/rotors, so installed and hooked everything up.
"Bench bled" the MC's in the car (supply and outlet ends into a reservoir higher than the MC's).
Then installed all of the fittings, and gravity fed as much as I could.
Next used a vacuum pump to pull fluid through to each caliper (in proper order, furthest to closest).
Rears still has SOME air that I couldn't seem to get out - but small amount so moved to the fronts
Fronts went pretty seamless, and had constant clear fluid.
Pedal was a little soft, but not bad - figured that was the air still in the rear lines.
Checked everything for leaks and all of my brake lines were solid (At this point, I'm thinking I'm a damned good builder!)
Figured I would finish bleeding them the ole 2 man method to get remaining air out of rears / final bleed before I installed panels around the foot boxes.

Then 2-3 months went by - and now I'm finally ready to install the panels, so I had my dad come by and help me do the final bleed.

Started with the rear. Rear brakes bled pretty easy, no air in the lines really. Figured I would make sure the fronts were also 98%, then come back and do all 4 corners one last time. Brake pedal is nice and hard at this point.

Open the bleeder screw on right side front caliper and begin bleeding that one..... hummm..... little air (more than I was expecting). Keep going through 10-15 cycles - getting MORE air than we started with? Now the pedal is SOFT. Making sure we always had plenty of fluid in the reservoir.

Scratch head for 10 minutes.

Start over on the fronts by pulling fluid through until little to no air. Pedal is firm (maybe not as good as the first go round, but 80%). Go back to open-pump/close release. Little air..... turns into MORE air..... Air is getting INTO the system, but no fluid is escaping anywhere other than the bleeder? Double checked all of my fittings from the reservoir to the MC and repeated. STILL air getting in.

I've gone through about 5 containers of fluid........ somethings not right!

Is it possible that if I didn't bench bleed the MC's right, that I could get this outcome? Bad Master cylinder? Rian is a dumbass and is missing something simple? .......now I'm thinking I'm an idiot builder.

My build is using a hydraulic clutch from Mike Forte, so I DO have a MC for the clutch that is installed but not in use yet (all 3 are 3/4", and I believe identical) - I suppose I could "trial and error" using that one. I have to admit that I'm feeling a little sketched out, and that's not a good feeling when assembling brakes....

Time for a beer brake and seeing if the forums can steer me - yet again - in the right direction!

Thanks all.

RR

[edwardb]

You don't mention it, but I'm assuming you're using the top bleeders on the Wilwood calipers. Assuming you never let the reservoirs go dry and don't have any leaks in the system, hard to know where air might be re-entering the system. There have been several reports of defective Wilwood M/C's (I was one of them) but don't see how that would cause air to come back into a system that previously had bled OK. Maybe someone sees it differently. The method you used for bench bleeding is the same as most of us, and has always worked for me. You've run enough fluid through there that all air should be out of the M/C's. I will only add that I've used pressure bleeding exclusively, and it's always worked with just a few bleeding cycles. There are commercial products (like Motive) but I just use a temporary cap on the reservoir with a Schrader valve and 5 pounds or so of pressure. No pedal pumping. Just keep the reservoir from running out, replace the pressure as needed, and go around following the usual pattern at the bleeders until no more air.

[F500guy]

If your reservoir is above the caliper, try cracking the bleed valve and let gravity do the work and drain thru the vent, no tubing on the vent and no brake pedal, let it drip and see if that works. Also ensure the balance bar is centered and you are not pushing to much on the rear compared to the front. That is my secret Miata bleed procedure

[Rian_Colorado]

Thank you both for your input!

Paul - yes, I'm bleeding via the top bleed screws, and I've checked for any leaks dozens of times (heck there would have to be fluid EVERYWHERE at this point - right!). Really, the only way that it's ever bled OK, is if I'm pulling fluid through. I don't have a system to push fluid from the reservoir, but I'm thinking about doing that for sure!
I'm at a loss as to where air could be getting into the system in such a way that fluid wouldn't be escaping? Granted, only things on the caliper side of the MCs is really "under pressure". Anything between the reservoir and the MC might only experience vacuum, but I would think that fluid would escape and leak anyhow if air could get in that way? That really only leaves the MC as a possible failure point, but it still doesn't make sense to me that air could be introduced without fluid also escaping.....

Sent an e-mail to Wilwood as well, we'll see what they think

Rian

[edwardb]

Thank you both for your input!

Paul - yes, I'm bleeding via the top bleed screws, and I've checked for any leaks dozens of times (heck there would have to be fluid EVERYWHERE at this point - right!). Really, the only way that it's ever bled OK, is if I'm pulling fluid through. I don't have a system to push fluid from the reservoir, but I'm thinking about doing that for sure!
I'm at a loss as to where air could be getting into the system in such a way that fluid wouldn't be escaping? Granted, only things on the caliper side of the MCs is really "under pressure". Anything between the reservoir and the MC might only experience vacuum, but I would think that fluid would escape and leak anyhow if air could get in that way? That really only leaves the MC as a possible failure point, but it still doesn't make sense to me that air could be introduced without fluid also escaping.....

Sent an e-mail to Wilwood as well, we'll see what they think

Rian

Just remembered from some threads on this topic in the past, FF and Wilwood suggest bleeding two wheels at a time with the Wilwood balance bar/dual MC setup. https://www.youtube.com/watch?v=jELllXdtjdc. I haven't done this since the pressure bleeding technique I use seems to work OK. But something to take a look at.