Help with braking issue. PLEASE. I am stumped at this point.

[73pony]

Help/Suggestions needed. 73 Mustang. Running 4 Piston Wilwood up front drums in the rear. Original disc brake car. After approx 500-750 miles on this set up the front right caliper hangs up after about 20-40 miles of driving. Park for a bit and it is fine until after another shortish drive. This was happening and I was troubleshooting this and had just replaced the MC about two years ago hoping this was the issue. Motor blew shortly after so I didn’t know if it fixed it or not. Well got the new motor built and in and sure as shit it is still happening. Wilwood has been zero help. Any suggestions on where to look or troubleshoot? I really want to get this resolved this week as I have been busing my ass trying to get it back on the road for this Saturday for a huge mustang show at Brownells. Thanks in advance.

 

[Bentworker]

How old are your brake hoses?

 

[Mac]

There is a master cylinder for cars with disc brakes and a different on for cars with drum brakes. Happened to me years ago. The parts store gave me one for drum brakes where as I have disc. Both look the same on the outside. Difference is internal where the disc brake one has a check poppet to relieve pressure. When you have a drum brake master cylinder on a disc car the pressure can’t be relieved, instead continues to build to where eventually the brake pads lock up on your rotors and brings you to a dead stop.

 

[73pony]

The hoses are new from Wilwood with the brakes. SS hoses. It is the correct Master. Verified the part number. Also it was doing it with the original master as well.

 

[boilermaster]

73pony,
Wilwood part number of your kit and Wilwood master cylinder number would be extremely helpful.
A few things come to mind here, what combination valve or proportioning valve ?.
Is it possible you have the right front caliper plumbed to the port intended for the rear brakes ?.
Also have you swapped calipers from side to side to see if the caliper swap makes the left side stick .
Also as a last resort, one could actually measure each piston ( fully compressed) to rotor surface (brake pads also removed) to see if you have equal spacing and that your piston bores are perfectly squared to the rotors surface.
How full do you keep your master cylinder and is there enough room for fluid to return when the pedal is released, and the brake fluid is hot ?.
Boilermaster

 

[Stanglover]

I'm just going to through this out there. When I did my front brake conversion, drum/drum car, I installed the SSBC 4 piston Kelsey-Hayes style front discs because they are a direct swap on drum spindles and also fit 14" wheels.
This kit came with a rear brake variable control valve and master cylinder. This bypasses the combination valve completely so it just becomes a junction block for the front brakes. The rears are totally separate.
Maybe splitting the system like that might help??

 

[MikeGriese]

How are your wheel bearings?

 

[Fabrice]

Not sure what you mean by hang. You mean it still stick/drags?
If of any help and applicable, have you lubed any guide/pin if any in these? Also if you used shims to center the calliper, you have the exact same amount on all guides around the pads?

 

[mrgmhale]

How are your wheel bearings?

No matter how they seem to be, it is good to pack them, and replace the grease seal, any time you do any kind of brake work. They are too often overlooked and taken for granted. Then the day comes when one seizes or blows apart... Go ahead, ask how I know this... heh heh...

https://youtu.be/pePLDeD2DMo

https://youtu.be/z_RwCz21LT4

 

[73pony]

Bearings are new and fresh packed. By hangs I mean it doesn't release all the way. The MC is a stock MC and stock proportioning valve. The car was original disc brake car. Wilwood Kit is 140-13477-D. 4 piston calipers. These were centered properly at install and rechecked when the problem started.

 

[boilermaster]

73pony,
Still thinking that you should swap calipers (and hoses) side to side to see if that will make the left side bind up.
That will break the issue in half and you will at least know which direction to work.
how old are the hard lines from the master cylinder forward ?.
any chance of debris in a hard line limiting return ?
same goes for the combination valve.
If it were mine and a caliper swap did not change the issue right to left, I would look at rebuilding or replacing that combi valve.
Boilermaster

 

[73pony]

My initial thought was that the braided line to the caliper is collapsing. I have a new set of those coming. I will try the Caliper swap if the problem persists after the line swap. All of the hard lines were flushed prior to installing the new kit.

 

[Bentworker]

How much pushrod play do you have between the booster and the MC?

 

[73pony]

How much pushrod play do you have between the booster and the MC?

About 1/16 ish.

 

[Bentworker]

Might be worth posting some pics of your brake setup to see if one of the forum eagle eyes spots an issue.

 

[73pony]

I will get some pics tomorrow on my lunch when I can get over to my shop.

 

[Stanglover]

About 1/16 ish.

It's not going to cure the problem, but I thought the push rod to MC was supposed to be 0 to about .010" clearance.
Just something I remembered about when I did my disc brake conversion. At first I installed nice shiny SS braided flex lines, but they didn't work worth a damn and I switched back to new rubber lines. Not had a problem since............. and that reminds me, time to do a front brake check.

 

[tony-muscle]

What brake pads are you using? Some of the racing ones tend to drag a bit after seeing some action.

 

[73pony]

What brake pads are you using? Some of the racing ones tend to drag a bit after seeing some action.

I am running the BP-10 compound.

 

[73pony]

OK Thought I would update this thread. I was sick for a couple days, so nothing was getting done. Felt better yesterday and decided to do some additional testing. Got the car up on the lift and the front tires off. Got in and pumped up the brakes. Cracked the bleeder screw on driver side, no squirt. Repumped for good measure and cracked the bleeder screw on passenger side. Lots of pressure. So IE there is something with caliper or the line that is holding pressure. Pumped up again and this time cracked open the fitting connecting the soft line to the hard line. No build up of pressure. IE its either the flex line or Caliper. Cracked the caliper side of the flex line and lots of pressure. Removed flex line completely. tried to snake a wire through it. Got about 3" from the caliper side and stopped. Tried to force it and could tell I was pushing into something. Pulled wire back and it had a small amount of soft rubber on it. Installed a new flex line and bled the brakes. Took out for a test run and NO ISSUES!!!! So I decided to wash it up last night as it was covered in over 2 years of dust etc. Ready for the IMU (Iowa Mustangs Unstabled) show this Saturday!!! I did do some careful examination of the old like and did not find any crush marks on the old hose but it was hard in the spot where I ran into the blockage. I will cut it open when I have time to see what it actually was.