Brake Bleed Trouble

[Adam7118]

Alright, I'm stumped. Maybe someone can help. I'm in the middle of a bronco/Coyote build and I can't get these brakes to stiffen up. The front brakes are from a 74 (knuckle out). Drums in the rear. All new lines with a wildwood master (not hydroboost). I have a proportioning valve from Classic Performance. The pedal springs back up but I can't seem to get enough pressure from a bleed to keep it from going all the way down to the floor. I've bench bled the master multiple times, bled the brakes with a mightyvac, bled them the old fashioned way multiple times, I used a proportioning valve bypass tool, I've adjusted the linkage at the pedal and the length of the throw rod for the master. Nothing seems to be working. Has anyone ever had this kind of trouble? Any thoughts on this? Thanks!

 

[ba123]

I've used a lot of bleeders over the years and since the first time I've pressure bled, I will never use any other method. I used a Motive bleeder and buying or making a cap to work for you is easy.

But...sounds like you might have a leak somewhere letting air in but who knows. Are your lines new or old? If new, I would highly recommend loosening all the fittings and retightening back and forth 3 or more times. Loosen, tighten-loosen-tighten.

You could try capping off either the rear or the lines at a junction along the way and see if the fronts work or capping off the fronts and see if the rears work. If neither of those work, you could go line by line. cap them all and then attach one caliper/drum at a time.

 

[Adam7118]

I actually have a motive, power bleeder, but I’ve had some trouble finding the cap for the Wilwood. I called them to see if they offered one and Wilwood at least doesn’t. The master has two compartments as well. Do you know where you got the cap?

 

[ba123]

Yeah, the cap they make sucks. I bought it and returned it without even trying. The thought of using chains to wrap around my master, assuming I looked at it correctly, just made no sense to me.

So, I bought an extra Wilwood cap, drilled and tapped an air fitting into it where one of the air holes is, and sealed the other air hole (small weld but might work doing something else like drilling, tapping and locking thread seal).

 

[brncofinatic]

Have you actually taken the hubs off to look at the breaks? I had this problem and couldn't figure it out until I took the hub off and one side of the breaks had come off. Reinstalled them and put the clip back on and it fixed the problem.

 

[Apogee]

Wilwood provides a recirculation bleed kit with their master cylinders, and while that method can work, I would recommend doing a plugged-port bench bleed instead. This process not only tends to work quicker since it's bench bleeding under pressure, but it also provides feedback regarding the internal seals that a recirculation bleed does not. If you're not familiar with a plugged-port bleed, it's just like it sounds. Hold the master cylinder in a vice by the mounting flange just like you would for any other method, plug both outlet ports with inverted flare plugs of the appropriate size (3/8-24, 1/2-20 and/or 9/16-18 SAE inverted flare), fill the MC a little over half full and then slowly stroke the piston and allow it to fully release back to the snap ring, waiting 2-3 seconds before stroking it again.

• The stroke length will decrease as air exits the bore and returns into the fluid reservoirs, until it hydraulically locks with minimal travel (1/16" to 1/8" is typical).
• Once the unit hydraulically locks and the piston can no longer be stroked, apply moderate force to the piston and hold for 15-20 seconds. If the piston strokes at all, then the unit is internally leaking fluid past one or more of the seals.
• Install the unit on the vehicle with the plugs still installed and top off the fluid.
• Connect one of the brake circuits to the MC while leaving the other plugged, and bleed that brake circuit fully until you achieve an appropriately high, firm pedal for the brakes on the vehicle. Different pedal/master cylinder/caliper combinations can result in different pedal feels, but it shouldn't be mushy or inconsistent or "pump up" with repeated application of the brakes.
• Connect the other brake circuit and repeat. By only working on one end of the vehicle's brakes at a time, you reduce the number of variables in play should troubleshooting be required.

There are various methods to bleed brakes, so pick your poison, but I still prefer a 2-man bleed so that I can get feedback on both the pedal feel and fluid at the same time on the same bleed. That said, pressure bleeders are great for filling up dry systems and even vacuum bleeders and reverse bleeders can come in handy in certain situations.

Tobin

 

[DirtDonk]

No hydroboost, but is it vacuum assisted, or manual?

Since Wilwood, is the front reservoir to the front brakes, or are you using the original rear reservoir to the front brakes?

You said "knuckles out" but also "from a '74" so do you mean you have Ford disc brakes from a '76 and newer? Or are you using the conversion kits using different calipers?

Paul

 

[73azbronco]

Toughest and most aggravating bleed job I've done, wildwood MC, proportioning valve, and front disk conversion. I used stock bleeder valves, spring loaded ones, etc. I will admit to having the calipers on upside, which I solved in 30 minutes, but for the next two days, my wife got real good at surfing facebook in the drivers seat while I bled it out. I finally broke down and bought a motive and pressure bled which solved the issue in 2 hours.

Buy the bleeder, make sure the master is really bench bled out, I did that mounted on booster with hose returning to res, over and over, let sit, over and over.

 

[Fastracer]

Having done complete brake line replacement on hundreds of vehicles whenever I had a stubborn one I used this to determine where the issue was. It takes the guess work out of it and only cost a couple bucks to make. Start at the master cylinder and work your way out to the wheels.

 

[Adam7118]

BA123: You could be right about air getting in, but there aren't any leaks. I might bite the bullet and get the cap for the wildwood with the chains and try pressure bleeding. I would make one like you suggested but if it isn't the issue I'll be kicking myself later.
Apogee: I did use the recirculation bench bleeder kit multiple times. It seemed to work, but I'll try anything. I'll give the plugged port bench bleed a try. Thanks!
Dirtdonk: It is vacuum assisted. And because of the wildwood, the reservoir chambers seem backward. So the rear reservoir should be front brakes. You're right about the axles. It is not a conversion kit.. I believe the axles would be 76' or newer.
73Azbronco.: Someone else also suggested the possibility that the calipers could be upside down. I wouldn't discount it as a possibility. Will check tonight. Also, yes I'm going to buy the bleeder cap. I have the motive bleeder already. Thank you!
Fastracer: This is brilliant. I'm going to put one together. I appreciate it.

Thanks everyone. I'll keep you updated.

 

[ba123]

Brakes are so temperamental that you could have a leak where air is getting in or maybe no leak and air is just stuck somewhere and keeping you from building pressure and pushing or pulling the air out.

The reason I think the Motive or any other pressure bleeding works is that you are literally pushing EVERYTHING in the line outwards one by one starting with the furthest line and working inwards.

Here is the post in my thread where I did mine in my build and shows my cap (click that line)


Honestly, just do it this way, you will be happy. Maybe a tiny bit more work getting it ready but you will be glad you did once you do it. It was SO easy and my brakes have been rock solid perfect ever since.

 

[gnpenning]

I don't think I saw what calipers you are using and if they are new or rebuilt. May not matter, either way I would pull the bleeder screws and cover the seal portion with dykem and if you don't have that a sharpie would work. Bleeder screws not seating and thread issues has been covered on here before, especially for rebuilt calipers.

You have several really good ways mentioned on how to isolate the issue and is a good way to know when you are going the right direction. While it's possible you are having trouble with both ends it's not as probable. If you are having trouble with both ends the master cylinder is the first place I would start. The close bleeding method is a good start.

 

[Otis Campbell]

How much distance do you have between the brake pedal and the floor? If I remember right, my kit called for 6.5" or so. If you are lower, you're not getting the benefit of the complete range of the MC piston and the pedal will not feel as firm as it should.

 

[ntsqd]

What bore size is your wilwood master cylinder? This could easily be contributing to the pedal feel if it is too small.

My own preferred method for bleeding brakes is the "peanut-butter" bleeder.

Tall tube has it's end submerged below the fluid level and it's hose pushed over the bleed nipple. Short tube does not and is only used when using engine intake vacuum to help with bleeding the brakes.

Using it is simple: slowly push on the brake pedal with the bleed nipple cracked open. Then slowly release it. Can do this by hand while sitting on the ground watching the bubbles in the jar. When no more bubbles, close the nipple and move to the next one.

Top-TIp: use a little bit of silicone dielectric grease in the threads (ONLY!!) of the bleed nipples. This not only helps seal the threads when bleeding (no false air bubbles), but it also helps keep the bleed nipples from rusting solid in the caliper or cylinder body.

 

[ba123]

I think you guys are getting off track a bit.

It's not about feel...yet...he doesn't have any feel cause the brakes aren't bleeding.

 

[ntsqd]

I don't think we're off track at all. Too small of a m/c can make the pedal feel mushy even when not fully bled. Which is why I asked what size it is. Need to know if we're fighting one battle or two.

 

[Otis Campbell]

I think you guys are getting off track a bit.

It's not about feel...yet...he doesn't have any feel cause the brakes aren't bleeding.

You may be right, wouldn't be the first time I've been off track! Unfortunately, I know first-hand how an improperly adjusted pedal can mimic a brake system with air in the lines. I originally adjusted mine for my own comfort which dictated a much lower pedal. Then I spent a lot of time scratching my head and bleeding and re-bleeding the brakes wondering what the heck? Once I readjusted the pedal to the prescribed height the pedal no longer felt squishy. Anyway, I hope my experience can help someone.

 

[73azbronco]

no feel=air in lines.