Brake bleed wilwood pedal box

[cfriedman67]

Hi all,

Im having some issues bleeding my brakes. I have a willwood pedal box, factory five rear brakes and rebuilt 13 inch 1996 mustang cobra fronts. The only brakes i have bled have been on a rebuilt 1978 honda cb750. What I have done is fill the brake reservoir with fluid, cracked the bleeder valve on one of the wheels, attached a hand held brake bleeder and vacuum pump. Although I seem to be creating a vacuum the level in the reservoir does not move. I've read about bench bleeding the MC, not sure how to do that or if it is necessary. If any one has some ideas it would be very welcome.

Thanks
Craig

[edwardb]

Bench bleeding is a bit of a misnomer because it can be done on the car. In fact that's how I prefer to do it. Less I handle brake fluid the better as far as I'm concerned. I'm not sure it's necessary for your vacuum setup. But I've not done vacuum bleeding and bench bleeding isn't hard. So it would be easy enough to try it and see what happens. Disconnect the brake line from one of the MC's. Replace it with a short piece of brake line that feeds into the open top of your reservoir. Then pump the brake pedal until you get a solid flow of fluid into the reservoir. Replace the brake line and do the same for the other MC. You should get a solid flow of fluid in each with just a couple pumps as the air is replaced with fluid. Then try your bleeding process.

[Railroad]

Make sure your master cyl push rods are adjusted to completely release the pistons in the master cylinders.
Most factory systems will gravity bleed. I have not tried the Wilwood, yet.

[RickP]

I had a heck of a time getting my brakes to bleed properly all the way around. In an attempt to do it myself, I first used a Mityvac handheld. That somewhat worked. I then purchased a vacuum type bleeder that I could hook up to my air compressor. I had better luck doing that but still the pedal was "squishy". I then replaced the bleed screws with "self bleeders" and had my GF operate the brake pedal while I held a hose in place. That turned out to be a disaster. "Honey, pump the pedal to the floor", "ok", "are you pushing the pedal in?" "oh, you me now", "yes dear, now". Yadda.

Paul's instructions on how to bleed the master(s) while installed in the car is exactly what I did before trying to bleed out any of the brake lines and in the end, I borrowed my buddy and got it done without any fancy bleeder tools. A piece of hose, two people, and some patience is all you need. Be sure you have you have NO leaks at any joints and then stick with it until that pedal is solid under your foot. Get a buddy to help and this task will be a simple one.

[cfriedman67]

Many thanks to Edward, Railroad, and Rick. I will follow your advice and hope for a successful outcome.

[GoDadGo]

I've had good results by simply doing an extended gravity bleed.

1. When I did the rear I did raised the front of the car a pretty good bit and started with the longest run.
2. Once I completed both the front and rear, I then did a regular (Pump It) bleed and the process was complete.
3. I did not bench bleed anything, including my hydraulic clutch set up.

Good Luck & Happy Brake Bleeding!

[CraigS]

One other trick w/ the Wilwood setup is to bleed one front and one rear at the same time. If you just do one, you often don't get a full stroke at the MC. The balance bar gets cocked and binds up the MC travel. This is more common after you have one system all bled so that the MC doesn't move very far and that restricts the travel of the other MC. A problem w/ vac bleeding is that the threads on the bleeder screws are usually a loose fit in the caliper. So you are sucking more air around the threads than fluid through the bleeder. I prefer pressure bleeding. I have a compressor and a pressure regulator so it is easy for me. W/o that, you can buy a small fish tank aerator pump and figure a bunch of hose, caps etc to connect it to the top of the reservoir. I use a 2 inch piece of radiator hose that fits over the reservoir and a couple of plumbing dept caps that fit inside the rad hose and get me down to a diameter that the air hose will fit onto.

[cfriedman67]

I was able to get the front brakes bled by using the power of gravity. The issue I am still having is with the rear brakes. The rear willwood MC filled up with brake fluid but will not travel any further. I removed the hard brake line from the MC to see if the fluid would come out when the brake was pumped but no luck. I looked at the master cylinder to make sure it was fully engaged when the pedal was pressed and as far as I can tell it was engaged. Is it possible the MC is no good?

[Duke]

^^^ I doubt you have a bad MC. I'm not sure I'm following how you are gravity bleeding as I haven't heard of that before. With pressure in the system, are you getting fluid out of the bleeder valve when cracked open?

I've seen a lot of comments and different approaches to bleeding brakes on this forum and I'm honestly not sure why. What I was taught and what I have done on dozens of different cars, hot rods, and race cars I always thought was pretty standard:

- Two people, a clear hose, wrench, cup, and fluid.
- Start on one bank (usually rear). Open the reservoir and fill it with fluid.
- Starting with the caliper furthest from the MC (usually passenger rear), have one person push the brake pedal all the way to the floor and hold it.
- Second person has a hose over the caliper nipple drained into a cup. Crack the bleeder open 1/4 turn. Close it.
- Driver releases the brake pedal, pushes it back to the floor and holds it. Crack bleeder, close, release brake.
- Repeat until solid stream of fluid without bubbles.
- Move onto the next caliper. Repeat.
- Move to the next bank (front) and repeat.

On my car it was about 10-12 full pumps to get fluid through the system. Craig's spot on with the wilwood balance bar. In a dry/new system it's not uncommon to go back around on all 4 corners after you've finished just to confirm the bar had enough stroke to push all the fluid/air out.

[CraigS]

.. I removed the hard brake line from the MC to see if the fluid would come out when the brake was pumped but no luck. I looked at the master cylinder to make sure it was fully engaged when the pedal was pressed and as far as I can tell it was engaged. Is it possible the MC is no good?

It is certainly possible but not too likely. I have two ideas for you; 1- check all the joints in the hard lines and soft lines MC to calipers. I just changed my rear MC to a different diameter and made a rookie mistake of not fully tightening a union on the hard line. I had run over a can of fluid through the rear system and had a puddle only 4 inches in diameter. Seems it sucked in more air than it leaked fluid out. 2- Get a short piece of hard line and some clear plastic tubing to make a bench bleeder line. Just 2 inches of hard line so you can make a near 180 degree bend and then a few inches of the clear tube to go back into the fluid in the reservoir. This allows you to easily see fluid and bubbles. Pump until there are no more bubbles which may be a LOT of pumps.

[cfriedman67]

hi CraigS and Duke, thanks for the advice as i will try that next weekend or two. My last question/comment is that I originally tried to bleed the rear as Duke suggested but noticed that I had a leak in the front driver side connection which I tightened and fixed. I then proceeded to finish the front bleeding. When I returned to the rear I still had no luck. I will go back and check the rear connections to make sure they are all tight as CraigS suggested. When pumping the brake pedal and detaching the hard line from the MC shouldn't brake fluid be forced out of the MC if it is working correctly? That is the only reason I had thought maybe the MC is bad because nothing comes out of the MC when the brake pedal is pumped and the hard line detached.

[Duke]

Make sure you have the cap off the reservoir when you are bleeding. That may be your issue with the rear. You could be creating a vacuum that is not allowing the fluid to move, and with a few air bubbles in the line you most likely won't get any fluid out of the MC when pumping.

[cfriedman67]

Thanks, I will try that as well. I might have had the cap on.

[edwardb]

When pumping the brake pedal and detaching the hard line from the MC shouldn't brake fluid be forced out of the MC if it is working correctly? That is the only reason I had thought maybe the MC is bad because nothing comes out of the MC when the brake pedal is pumped and the hard line detached.

Yes. If there is fluid in the reservoir and properly connected to the MC, the brake line disconnected, and a temporary line from the brake line connection back into the open top of the reservoir (better known as bench bleeding) you should get a solid stream of fluid into the reservoir when you push the brake pedal. I've never had it take more than a couple strokes to prime and start working. If it's not working that way, something isn't right.