Technical Just another idiot with tools....

Good morning, I’ve been struggling with getting my brakes to actually lock up when I fully press the pedal. It’ll stop under normal circumstances, if I press the pedal and then start the pickup the pedal sinks.....

- I’ve bleed them with a Motive vacuum
- I’ve had a shop (while getting it dyno tuned) vacuum bleed it with a Mighty Vac
- I’ve pump pump pump hold crack etc.....
-I’ve added a vacuum tank....that didn’t work. It barely started, drove the truck down the street and when I tried to lock up the brakes the truck died.

So yesterday I made a longer rod between the booster and MC. It was about 3/16” longer and when I bolted the MC back onto the booster I could tell it was slightly too long but I could still spin the front drivers wheel.....thinking the brakes were loose....I took off down the street and after about a mile of pressing the pedal and speeding up I let off the gas pedal and I noticed the truck would nose dive a little. Well that’s not right so I turned around and could feel the truck being held back.

I haven’t put any wood to cover the bed and I kept looking over my shoulder because I could smell something “burning” ya know like brakes. Well shit here we go. I could see smoke, then sparks then flames coming off the passenger caliper. I made it home and ground off the 3/16”........ back to “normal” but not fixed.

I’ve decided to stop being lazy bastard and bleed my system until my own fingers bleed! I’ll also recruit my Dad when he’s visiting this week to pump pump pump pump....

The best part was hearing my 8 year old son recount the story to my wife over the phone! I’m glad he didn’t repeat the part where my language went from shit shit shit shit to f*ck f*ck f*ck......

Anyways that’s how my Saturday went, just trying to burn my truck down


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Well, your clearly Shooting in the Dark. Were I to guess I'd say you bought into the aftermarket Brake suppliers line of "Here is a Kit for ya" and you didn't know they were pumping you full of Shit just to raid your wallet. Once owning and installing things your now on a mission to make it work and you don't have a Clue. I've been on the H.A.M.B. for 18 years and you are just another repeat story of the other Hundreds just like it. If you really want some help you need to bring those that can up to speed as to just what parts you have mixed-n-matched together. Your exact symptoms have been talked to death here and just hitting the search menu will bring up lots of info, however you still will need to weed out the Stuff that isn't going to get you anywhere. List your parts and let's see where this goes.

 

You might try starting with putting a pressure guage on your master cylinder and finding how much pressure its putting out. You didn't say whether the pedal sinks all the way to the floor or just sinks a little. I would also add a
temporary vacuum guage so you can see what happens there. You can always take an old brake drum and cut the face of it out with a torch. Then you just have an open faced ring. Slip it over the rear brake, and when someone steps on the brake you can see what the brake on each wheel is doing. Once you know the rear brakes are functioning properly,
then move to the front system.

 

I have to ask this after reading your opening line;

Did you install the check valve in the Booster. If not every time you start the Motor you have to re charge it. Doing that will cause the pedal to move.

 

When you installed the longer rod it prevented the master cylinder from retracting fully and opening the port to the reservoir. That means the pads can't retract. They get hot, brake fluid expands, pressure increases, everything gets hotter and pretty soon...poof.
regards,
Phil

 

What kit did you buy?
What calipers are you using?
Metric? Low drag ?
Master cylinder bore size?
Booster size? Duel?
Check valve ? Correct hose? Not collapsing?
Wheel cylinders?
Check valves?
Prop valve?
And bulkhead fittings?
Under floor or fire wall mount master?
Pedal used?
Tuna sandwich or salami on rye?
We need more info and pics of the install would be great.
Neat looking truck !

 

I’ve assumed the port in the booster where I connect the vacuum line has the check valve....after I drive the pickup around I pulled the line off the carb and it hissed like it was holding pressure

 

Video was a little bit interesting but... hasn't the guy ever heard of bench bleeding the master cylinder and putting some plastic/rubber hose on the wheel cylinder bleed valves when bleeding th brakes? And I was taught to bleed the various wheel cylinders starting with the furthest from th master and making my way to the closest.

 

This result means the check valve isn't doing it's job.

This is pretty basic knowledge for those of us that already know. Sounds like he may never have been exposed to how things are done and would like to know. Weren't you there at some time? I know I didn't come along already Smart.

 

Sounds like you need to make sure your starting and running issues are a separate issue. Were it me I remove the 3/8" hose that goes to the Booster at the manifold and plug that port. Now start the motor and make sure things there are doing what there supposed to do. Next reconnect the hose. If the problem returns you have a Booster or connecting line issue. Rule of thumb for me is to not have more that 6" total of rubber hose doing any single job connected to the Motor.

 

I can see the problem from here, he needs to be working on his AVATAR car.......................................

 

Brake systems that are set up right are easy to bleed, there's no need to bleed over and over again.

Like he said, more info about what parts you have on the truck, would be a big help.

 

You have a beautiful truck.
Hope you get it figured out. There's a lot of knowledge here.

 

What you are describing sounds a lot like a bypassing lip seal in the master cylinder. One of the checks I've done for years is to make a hard application, vehicle setting still, then slowly start to release the pedal pressure. If the pedal drops, it's got to be the seal in the master cylinder bypassing. Just diagnosed a bad clutch master in my buddies 34 using this method. Found a deformed seal when we disassembled it.

 

And did you adjust the rear brakes?

 

Are the lines ran to the appropriate reservoir, do you have residual pressure valves, what kind of proportioning valve, is your booster/master frame mounted or firewall ???
So many thing you left out.

 

I'm not big on the "one size fits some" brake kits. I go with factory stuff like masters and a booster if I need one. Right off Rock Auto sometimes. I used to do front disc swaps 100% out of the junkyard and they always stopped well. Proportioning valves/distribution blocks, real simple too. I used an aftermarket CPP one from Summit on my car. AND I keep the rear drum brakes. If my car came with all the front drum stuff, I may have kept it drums. I used a kit to convert to front discs... a real crappy kit that I had to make it work.

 

Good morning, I’ve worked with the tech’s at Wilwood and I’m still having the same poor brake performance.

I currently have:

Stock mustang II single piston calipers that are 2.5” diameter on the front

A SSBC “kit for a 10/12 bolt Chevy” that consists of a 1994-2000 mustang rear disc caliper that is a single piston with a 1.5” diameter

I have 3/16” brake lines everywhere and a coupler going to the front passenger side and another coupler going to the rear before it T’s and a T-block in the rear splitting left and right.

I have the Wilwood proportioning valve hanging off their master cylinder.

I removed the 2lb residual check valves when I moved the pedal assembly off the frame and up onto the firewall.

I have a firewall mounted Wilwood pedal with a 6.5:1 ratio and have used a Wilwood 7/8” bore and a 1” bore remote reservoir master cylinder. I no longer have a vacuum booster as I was only getting 10” of vacuum off the manifold...I’m running a Weiand 177 blower. So I have full mechanical brakes....

When I bleed the system I get a good stream of fluid and I push at least 6oz of fluid through each caliper which is past having air bubbles but I’m paranoid....


So, with a frame mounted pedal/vacuum booster along with an electric vacuum pump pulling 18” - 20” of vacuum and a stock GM corvette style MC....then I changed to a Wilwood 1” bore remote MC.....then I figured out I could only push the rod into the MC roughly 5/8” instead of a 1-1/8” because the pedal couldn’t swing that far....I changed to the Wilwood 6.5:1 firewall mounted pedal and per their advice used a 7/8” MC .....that didn’t work either so they said try a 1” MC........I still can’t “stop” I can barely slow down. In fact when on jack stands and my wife holding the pedal down I can with all my might spin the wheels.


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Has this been on the car the entire time? Seems like you have changed everything else.

 

I had a frame mounted JEGS block before

 

This won't help the OP specifically , but here's a thought. I'm a huge proponent of simplicity , saying that ; if you use mustang II calipers , why not use a mustang II master & pedal ratio & combo valve & rear brakes , match the parts of the system like the OEM did ,or at least match up the bore sizes . I know the "in" thing is disc rears but drums work just dandy unless you're on a road race track . KISS principle , just makes life easier ( and. safer)

 

Yes sir....I attempted to follow the OEM design by having Wilwood dictate the MC size as it compares to my calipers...at least that’s what they said to do.

What they kept telling me was the diameter of the caliper pistons was HUGE and it was going to take a lot of volume. I’m wondering if I went to a smaller 4 position caliper up front it would help..??..but that’s a whole lotta money to gamble with!

 

I have learned most of the time, Wilwood's default go to size seems to be 1". When you receive their product the little fine print will say that they will not be held accountable for any info given from tech over the phone.

I would do what is suggested in post #3, get a pressure gauge and get some pressure readings. Yes, it's a pain but should give you a better understanding of what's going on..................................

 

Just re-reading this thread and saw your reply. I believe my comment about the sequence was directed at the video not the OP. As to coming along smart I came out of the womb a smart ass!

 

Mustang II MC bore size is 15/16" , if yours is larger it will take less movement & more foot pressure applied than stock. What are your rear calipers from ?

 

Smart ass is better than a dumb ass! These damn brakes make me feel like a dummy

 

A 94-2000 mustang rear disc....must have been the cobra or Shelby series.

 

Have you adjusted the rear calipers? They have to be close to right to work at all.

 

Yes, I have. I don’t currently have an emergency brake hooked up but I pulled the arm out on each side until the pads wouldn’t move in any more

 

Wilwood said I should be creating 1000psi with a 1” bore MC. Is that divided by 4..??..or should I see 1000psi at each caliper?