Brake MC failure?

[Kivyee]

Hello Forum,
I decided to bleed my brakes last night - Wilwood pedal box with wilwood dual MCs for the brakes. I was going to do a gravity bleed but then use a hand vacuum bleeder to help increase the speed - after buttoning it up I found that the pedal would get firm about an inch down but would continue to go all the way down with firm pressure. Tried it about 3 times pressing with probably 30% of the force of what I would consider "hard braking". Decided to involve my kids and do the regular pedal assisted brake bleed, from and rear brakes being bled at a time. When my son mentioned the pedal suddenly got easier to push, I buttoned everything up, and sure enough, the brake pedal now goes up and down with almost no resistance. No leaks anywhere.

All things point towards the MCs being done for, correct? 8k km on the car, built by PO in 2019. Now I have the fun job of swapping out the MCs with the body on - but the silver lining is that this happened in the garage and not out on the road.

Leaning heavily towards going towards the tiltons.

[cv2065]

Hello Forum,
I decided to bleed my brakes last night - Wilwood pedal box with wilwood dual MCs for the brakes. I was going to do a gravity bleed but then use a hand vacuum bleeder to help increase the speed - after buttoning it up I found that the pedal would get firm about an inch down but would continue to go all the way down with firm pressure. Tried it about 3 times pressing with probably 30% of the force of what I would consider "hard braking". Decided to involve my kids and do the regular pedal assisted brake bleed, from and rear brakes being bled at a time. When my son mentioned the pedal suddenly got easier to push, I buttoned everything up, and sure enough, the brake pedal now goes up and down with almost no resistance. No leaks anywhere.

All things point towards the MCs being done for, correct? 8k km on the car, built by PO in 2019. Now I have the fun job of swapping out the MCs with the body on - but the silver lining is that this happened in the garage and not out on the road.

Leaning heavily towards going towards the tiltons.

Definitely sounds like the MC if you've bled it out and it just goes to the floor. Even with some air in the system you should get a little resistance. If you didn't build it, I'd probably still go through your lines/fittings and ensure that there no smaller leaks that may prevent the system from pressurizing. Regarding the Tiltons, they are plumbed a little differently than the Wilwoods, so mileage will vary build to build around how easy they are to swap. Also, adjusting the clevis rod on the Tilton is not as easy as the Wilwoods as there is no flat spot for the wrench, and getting your hand up there will be challenging. I have a Tilton for my clutch and still not 100% sure how I'll get it out if it ever needs to be replaced. Just my two.

[M22_COBRA]

Is there a preferred method to turning the threaded rod? Mill a flat? Make a screw driver notch at the end of the rod? Triple jam nuts? Or just plain old by hand (grippy grippy)

[EK1965]

I was able to swap both the masters to Tiltons....some disassembly required! If I recall it can be done through the dash and cover. Lots of different wrenches (angles & lengths) needed to get into the space and turn nuts and the order of installation mattered as some bolts became inaccessible but of course I can't recall which became problematic and what order I used. After install I removed the mounting plate below that the pedal assembly attaches to because there was a leak & poor routing of the hard line, but it was not needed for the replacement. Good luck and keep some bandages handy. I also replaced the c-clip style pins with cotter pins at the pedal end of the masters and pivots (macster carr precisions pins) of the pedal assembly. Much much easier to install.

[EK1965]

Is there a preferred method to turning the threaded rod? Mill a flat? Make a screw driver notch at the end of the rod? Triple jam nuts? Or just plain old by hand (grippy grippy)

My Tilton rod had a milled notch inboard near the master end that fit a wrench

[cv2065]

My Tilton rod had a milled notch inboard near the master end that fit a wrench

Must depend on the model as the 75 series does not.

[rich grsc]

You sure you didn't pump to all the fluid? If the MC are leaking, there should be fluid inside the foot box?

[Mike.Bray]

You sure you didn't pump to all the fluid? If the MC are leaking, there should be fluid inside the foot box?

It's probably leaking internally, bypassing. Pretty common on the Wilwoods since the bore is just a machined aluminum casting.


https://youtu.be/Hz4AlAt7DJ8?si=SjJiIfOXIm0hOzYO

[Kivyee]

It's probably leaking internally, bypassing. Pretty common on the Wilwoods since the bore is just a machined aluminum casting.


https://youtu.be/Hz4AlAt7DJ8?si=SjJiIfOXIm0hOzYO

Yes I believe leaking internally - before it went completely no resistance, there was steady resistance while still allowing continued pedal movement, which to me indicates leak past internal seals.

[M22_COBRA]

Bores like this... That's how.
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[CraigS]

Both MCs died at the same time while they were being bled? Doesn't seem very probable to me. A couple of thoughts; -W/ the dual MCs it is usually suggested that both left sides be bled at the same time and both right sides at the same time. If you just bleed one wheel at a time, that MC may not go to full travel since the balance bar may be stopped by the other MC which isn't moving since none of it's bleeders are open. -When doing a 2 person bleed it is critical that the pedal be held to the floor until the bleeder is closed. I do a call out by both pedal man (PM) and bleeder man (BM) for each action. Especially at the beginning PM needs to pump the pedal several times not too quickly until he feels just a little resistance and hold it down. Now BM can open and close the bleeder. He should close the bleeder while there is still a trickle of fluid moving so a tiny drop of air doesn't wick it's way back into the bleeder. So it goes like this. PM says 'pumping' then he says 'holding'. Then BM says 'opening' followed by 'closed'. Once PM hears 'closed' he can start again with 'pumping'. Note that, at the start, PM will feel almost no resistance to the pedal since he is just compressing air. Hopefully, as the process goes on, he will start to feel some resistance near the bottom of pedal travel and that resistance point will keep getting higher off the floor. Best wishes to you.

[Kivyee]

Both MCs died at the same time while they were being bled? Doesn't seem very probable to me. A couple of thoughts; -W/ the dual MCs it is usually suggested that both left sides be bled at the same time and both right sides at the same time. If you just bleed one wheel at a time, that MC may not go to full travel since the balance bar may be stopped by the other MC which isn't moving since none of it's bleeders are open. -When doing a 2 person bleed it is critical that the pedal be held to the floor until the bleeder is closed. I do a call out by both pedal man (PM) and bleeder man (BM) for each action. Especially at the beginning PM needs to pump the pedal several times not too quickly until he feels just a little resistance and hold it down. Now BM can open and close the bleeder. He should close the bleeder while there is still a trickle of fluid moving so a tiny drop of air doesn't wick it's way back into the bleeder. So it goes like this. PM says 'pumping' then he says 'holding'. Then BM says 'opening' followed by 'closed'. Once PM hears 'closed' he can start again with 'pumping'. Note that, at the start, PM will feel almost no resistance to the pedal since he is just compressing air. Hopefully, as the process goes on, he will start to feel some resistance near the bottom of pedal travel and that resistance point will keep getting higher off the floor. Best wishes to you.

Yes I was doing the same side, FR, at a time, and the hoses were also pointing up and into half filled bottle so that only fluid would get sucked in if coordination was off. Brake fluid canister also never ran dry. Yes it does seem unlikely to have both fail at the same time, but I'm actually wondering if one might have already failed before I got the car.

[cv2065]

Yes I was doing the same side, FR, at a time, and the hoses were also pointing up and into half filled bottle so that only fluid would get sucked in if coordination was off. Brake fluid canister also never ran dry. Yes it does seem unlikely to have both fail at the same time, but I'm actually wondering if one might have already failed before I got the car.

I’d pick up a pneumatic bleeder and try that before I started swapping out MCs. As Craig said, it would be unusual for both to fail at the same time. Harbor Freight has a good one for $99.

[CraigS]

One other thought re caliper position. My memory isn't real strong on this so bear with me. There were some calipers where the bleeder should not be pointed up. A quick diagram
224508
Here you can see that the opening inside the caliper, at the bore circumference, that fluid flows to the bleeder through, is at the top but the bleeder is pointed sideways. I wish I remembered which caliper this applies to but I don't.

[magicmarto]

Look up 40 Watt Garage on YouTube. He did a complete series on this issue.....Very detailed and very good.
https://www.youtube.com/watch?v=uzE-3M8LZzc&list=PLGWYUGGhs7StsczTH-ybBxA9IGou_OpBc

https://www.youtube.com/watch?v=uzE-3M8LZzc&list=PLGWYUGGhs7StsczTH-ybBxA9IGou_OpBc

[Mike.Bray]

Look up 40 Watt Garage on YouTube. He did a complete series on this issue.....Very detailed and very good.
https://www.youtube.com/watch?v=uzE-3M8LZzc&list=PLGWYUGGhs7StsczTH-ybBxA9IGou_OpBc

https://www.youtube.com/watch?v=uzE-3M8LZzc&list=PLGWYUGGhs7StsczTH-ybBxA9IGou_OpBc

Pretty interesting. I didn't see him ever mention the mileage on the car, seriously doubt it's 100k+. Why would all three master cylinders fail? Things that make you wonder.

[Kivyee]

I’d pick up a pneumatic bleeder and try that before I started swapping out MCs. As Craig said, it would be unusual for both to fail at the same time. Harbor Freight has a good one for $99.

Yeah that's a good thought - worst case is I'll have a power bleeder for when I install the new MCs, which would probably be good to have anyway. Hopefully the 45mm caps on those pressure bleeders fit!

[Mike.Bray]

I made a cap for my Scott's reservoirs.

224523

[Ejzajac]

It appears is a popular brake bleeder system.
Does anyone know the correct cap adapter for the standard FFR reservoirs OR Tilton triples?

Ed Z

[cv2065]

You won’t need a custom cap for the HF version. It bleeds from the caliper and the reservoir just needs to be checked after each corner. I think I refilled front and back twice for the entire process.

[Mike.Bray]

You know on these cars, assuming the master cylinders have been bench bled, you can gravity bleed and get 90-95% there. Mother nature's gravity will do the work for you, just takes a few hours.

[OB6]

You know on these cars, assuming the master cylinders have been bench bled, you can gravity bleed and get 90-95% there. Mother nature's gravity will do the work for you, just takes a few hours.

I'll second that, and in fact for me gravity bleeding has been the most effective method in most cars I've done. On my old Miata, I'd just put a container under each caliper and open them all up at the same time. Same with my truck.

[cv2065]

For me, initial gravity bleed is too slow. The pneumatic bleeder is a couple of minutes per corner. All done in 15 and that includes refills. However, I do a double 'bubble' check with a small gravity bleed cannister at the end.

[OB6]

For me, initial gravity bleed is too slow. The pneumatic bleeder is a couple of minutes per corner. All done in 15 and that includes refills. However, I do a double 'bubble' check with a small gravity bleed cannister at the end.

It's indeed slow, but I just do it while I'm putzing around with other things in the shop.

[Kivyee]

Welp it looks like Craig called it and thanks CV2065 on the idea to pressure bleed them. After doing another bleed with a pressure bleeder I have regained my brake pedal. Looks like air was introduced somehow to the front and rear system at the same time. Apparently the PO didn't hose clamp the brake hoses going from the reservoir to the tee to the MCs, wonder if vacuum bleeding it sucked in air to the MCs?

Guess having my 12 and 10 year old to help w the bleeding might not have been the best idea despite my excellent instructions :rolleyes: I still feel some sponginess in the brakes so I'll probably try a "real" power bleeder next. I 3d printed a cap with a barb to get going, partly thanks to Mike's inspiration ;) I was paranoid about the rubber brake hoses blowing off so I made sure it stayed under 15psi. Yes that's an airline going to a digital tire inflator that has a pressure set-point. :cool:

224595

[Kivyee]

It appears is a popular brake bleeder system.
Does anyone know the correct cap adapter for the standard FFR reservoirs OR Tilton triples?

Ed Z

The FFR reservoirs should work with the common 45mm euro adaptors. There was some air leakage in mine but it was likely due to 3d print tolerances and not having the best gasket in mine.

[Mike.Bray]

Welp it looks like Craig called it and thanks CV2065 on the idea to pressure bleed them. After doing another bleed with a pressure bleeder I have regained my brake pedal. Looks like air was introduced somehow to the front and rear system at the same time. Apparently the PO didn't hose clamp the brake hoses going from the reservoir to the tee to the MCs, wonder if vacuum bleeding it sucked in air to the MCs?

Guess having my 12 and 10 year old to help w the bleeding might not have been the best idea despite my excellent instructions :rolleyes: I still feel some sponginess in the brakes so I'll probably try a "real" power bleeder next. I 3d printed a cap with a barb to get going, partly thanks to Mike's inspiration ;) I was paranoid about the rubber brake hoses blowing off so I made sure it stayed under 15psi. Yes that's an airline going to a digital tire inflator that has a pressure set-point. :cool:

224595

The instructions on the pressure bleeders say to do it wet, what a mess and waste of brake fluid. I did it dry with no issues, you just have to be careful and not run the reservoirs dry, do a couple of cycles and refill.

[cv2065]

Glad it worked out!

[Ejzajac]

The FFR reservoirs should work with the common 45mm euro adaptors. There was some air leakage in mine but it was likely due to 3d print tolerances and not having the best gasket in mine.

Thanks for the info on Motive cap adapters.
NO spare juveniles around the shop, so I probably need a bleeder sytstem.

Ed Z

[Kivyee]

So now that I have taken the cover off the brake MCs I see that the balance bar is screwed up. Looks like PO didn't rtfm and basically set the whole thing up with no spacing between the clevices and the pedal arm, let's alone .2". I've managed to disconnect the MC pushrod (also suspect it wasn't shortened) by unmounting the MCs. My problem now is that the clevice is stuck to the balance bar, and since everything is so tight it's jammed up. My original thought was to basically slowly rotate the clevice and balance bar (together, clevice alone, together...rinse and repeat) to eventually get to the right spacing. I removed the locking setscrew in the clevis, but the clevis seems like it's still "stuck" to the bar.

It looks like I might need a jamnut against the jamnut to rotate the balance bar. Question is, are the locknuts on either side of the spherical bearing at the pedal arm locking onto the balance bar?

Any ideas on a good way of getting the desired clevis spacing without hopefully disassembling more things in really hard to reach places?

Here's a picture of the unbalanced bar for your reference

224615

[jengum]

Pretty interesting. I didn't see him ever mention the mileage on the car, seriously doubt it's 100k+. Why would all three master cylinders fail? Things that make you wonder.

In Part 3 he mentions using fuel rated hose between all the remote reservoirs and MC's which was responsible for creating the gunky black mess. He switched out all the hoses to EPDM rated. Lessons learned.

[2nd2none]

I've managed to disconnect the MC pushrod (also suspect it wasn't shortened)

With the pushrod, do most people actually follow the assembly manual and shorten it by the 5/8" that it calls for? At the build school, I recall them mentioning they didn't cut it at all and if you do, only cut off about 1/4". Does this change if using Tilton MC's?

[rich grsc]

Well why would anyone follow the assembly manual for something like brakes ? :rolleyes:

[jengum]

I swapped out to the Tilton 75 series for all 3 MC's on my build. I compared the push rod lengths between the Wilwood and Tilton bodies and they were roughly the same. So I trimmed a heavy 1/2" off of all 3 Tilton push rods following the recommendations in the build manual to trim the push rods. This leaves 1-2 exposed threads for all 3 MC's past the clevis...the build manual recommended flush with the clevis. Currently the brake pedal arm is just behind the horizontal tube and the clutch pedal is roughly 2" higher than the brake pedal as the build manual recommends. I did not bleed the brake system yet. I did not attend the build school either so cannot comment on their recommendations.

[Mike.Bray]

I swapped out to the Tilton 75 series for all 3 MC's on my build. I compared the push rod lengths between the Wilwood and Tilton bodies and they were roughly the same. So I trimmed a heavy 1/2" off of all 3 Tilton push rods following the recommendations in the build manual to trim the push rods. This leaves 1-2 exposed threads for all 3 MC's past the clevis...the build manual recommended flush with the clevis. Currently the brake pedal arm is just behind the horizontal tube and the clutch pedal is roughly 2" higher than the brake pedal as the build manual recommends. I did not bleed the brake system yet. I did not attend the build school either so cannot comment on their recommendations.

I did the same with my Tilton 76 master cylinders and have about the same results.

[CraigS]

For others reading this thread about pressure bleeding this is my adapter air hose to reservoir.
224661
Make it from any rubber hose you have since all it holds is air. I happen to have a regulator to drops my normal shop 125# air down to 5# so that makes it easy. OTOH at a friends house we used a fish tank air pump which worked fine.

[Kivyee]

Here's an update - I finally managed to get the clevis spacing set properly on the balance bar - you basically have to remove both MC pushrods - the rear brake clevis has just enough room to spin around the balance bar, which then allowed me to spin the balance bar to gain some separation between the front brake clevis and the spherical bearing (which was originally jammed tight together). I also had to unmount both brake MC's to allow enough room to remove the pushrods from the clevis - as you can imagine this is lots of fun to do with the body on, but a 1/2" crowsfoot wrench was a huge help.

Now that my balance bar is properly adjusted, I can see that I still have an issue in the rear brake system.

https://youtu.be/m_OOocx2UVA

The front brake engages and the rear brakes continue to the end of the range - Getting someone to press the brake pedal, I can still spin the rears by hand, while the front is unmovable. Which leads me to think that
a. I either still have air in the rear brakes
b. My rear MC did fail

I plan on getting some more brake fluid and to bleed the rear brakes again. I suspect that the car has had a rear brake issues before I got it - there were some rust on the rear rotor working surfaces while none on the front rotors. I'm hoping to avoid having to get a brake pressure gauge (likely very infrequently used tool) so would appreciate any more troubleshooting ideas. Thanks!

[Kivyee]

Glad it worked out!

Was doing some more research and you are describing the same problem as I have

https://thefactoryfiveforum.com/showthread.php?30561-Rear-Brake-Problems&highlight=bleeder+screw

How did it finally get resolved? Did you swap MCs? I'm about to try bleeding the rears with the e-brake engaged and see if that helps.

[cv2065]

Was doing some more research and you are describing the same problem as I have

https://thefactoryfiveforum.com/showthread.php?30561-Rear-Brake-Problems&highlight=bleeder+screw

How did it finally get resolved? Did you swap MCs? I'm about to try bleeding the rears with the e-brake engaged and see if that helps.

Wow, totally forgot that. Great thing about this forum is the historical searches for just about anything you want. In that case, I ended up purchasing two new rear calipers, as the bleeding valves had excessive play and were leaking. FFR did send me a new MC but that wasn't the issue. Once the new calipers were in place, the pedal was rock hard. Can't recall if you have the mustang brakes, but something to check.

[Kivyee]

Apparently I have the 88 thunderbird calipers (what comes in the brake kit) I have pressure bled the system more, actuated the parking brake multiple times and also bled while the parking brake was engaged. Now the pedal is definitely firmer and the MC movement is definitely more normal. I am also now unable to turn the rear wheel while the brake is depressed. The brakes however still feel somewhat spongy.

I'm going to leave it as is for now, hopefully get some driving/braking in then come back to evaluate it.

[cv2065]

Take a blue shop towel and blot around the bleeder valves on the caliper after pushing in the pedal a few times and see if you have any weeping around the valve.

[Kivyee]

Take a blue shop towel and blot around the bleeder valves on the caliper after pushing in the pedal a few times and see if you have any weeping around the valve.
Did check this no leaks at all
It was interesting to note that my driver's side rear caliper bleed screw has a lot more "wiggle" once loosened vs all my other calipers. Another thing to budget for...

Here's an updated video for the current brake situation.
https://youtube.com/shorts/sDohOLyo5aA

[rich grsc]

Bleeders DON"T seal at the threads, they seal on the cone shape on the bottom

[Kivyee]

Bleeders DON"T seal at the threads, they seal on the cone shape on the bottom

Yes, my concern with a "wiggly" bleeder is that it is now easier to deform the threads and ruin the caliper while sealing the bottom cone.

[Kivyee]

Slight update is that I was able to get the car out around the neighborhood to test some braking, so unfortunately wasn't able to get too fast but from 30mph I am able to lock up the front brakes, and the rear brakes were working, as confirmed by my very scientific thermometer app on my phone (i.e. Front rotors temp were higher than rear, which were higher than ambient temp). I'm going to tweak the bias slightly rear and test again the next dry day, and then probably re-bleed everything once I get some additional miles on it.

So in summary:
1. The initial bleed introduced air into the system, potentially front and back, resulting in complete loss of pressure in both MCs.
2. My balance bar was completely out of adjustment with both clevises jammed tight against the spherical bearing. The jam nut was completely loose but I suspect the clevis spacing wasn't set properly to begin with.
3. After properly setting the balance bar, I was able to see that the front MC was functioning properly.
4. After rebleeding the rears with parking brake actuation (repeated actuation, bleed while engaged, some pedal pressure while engaged) the balance bar orientation relatively to the firewall was now stable while the brake pedal was depressed.
5. The brake still doesn't feel "rock hard" and has some sponginess, but it's a matter of tweaking at this point.

Thanks everyone for their help!