Front Disc Brake Conversion | Questions After Reading Posts and Watching YouTube

[SLOWnEASY]

Thanks that makes sense now and definitely something sounds wrong. When you pull the master cylinder off again you should be able to remove the snap ring from the pushrod end and pull the piston out of the master cylinder. Lay the parts on the bench in the order they are removed and if necessary take a picture for reassembley. Then you can inspect the seals and the bore for damage or machining junk.

 

[jscheier]

Vs. just tossing it into the trash I will most likely pull it apart just to satisfy my curiosity. I've NEVER had any brake system fight me like this one (well, other than plumbing 1995 Cobra ABS into my 86GT... but most of that was trying to get the ABS brick to bleed).

 

[SLOWnEASY]

Lol yes, just to satisfy your (and our) curiosity to see if you can find a torn seal or something.

 

[jscheier]

Wilwood stuff showed up last night, so I got to work. Pulled the old MC, lines to prop valve and the prop valve itself. Disconnecting the prop valve rear line (going to the rear brakes netted no fluid leak. Disconnecting the front prop valve line (going to the front brakes) yielded fluid. Pulled the brake switch and could see the valve and it looks to be centered in the hole. Started installing the Wilwood MC, adjustable prop valve and the frame mount for the lines. Hope to get the MC bled tonight. The included bleeding instructions are pretty thorough as are the pedal height adjustment instructions.

Gotta get it stopping tonight as I need to get another car on the lift tomorrow.

 

[JeepGuy]

If you plugged both/all holes on the MC and pushed the brake pedal down, you should have had very little to no movement at all. But it sounds like you did have movement and the pedal eventually went all the way to the floor. Sounds to me like a bad MS. I'm still curious where that fluid was flowing with the holes plugged and pedal being depressed.

 

[Bruners4]

This might explain it best.

Can a Master Cylinder Fail Without Leaking? Symptoms, Causes & Repair Guide

A brake master cylinder can fail internally without visible leaks, causing spongy pedals, sinking pressure, and unsafe braking. Learn the causes, warning signs, and how to diagnose this hidden failure. CHBRAKECYLINDER master cylinders use Datwyler seals, anti-corrosion finishes, and 100%...

www.cnbrakecylinder.com

 

[jscheier]

Well, good news! Got the Wilwood stuff installed yesterday. Was immediately able to gravity bleed all 4 corners without issue. Locked it all down and then did the old 3-pump-dump with my son on the pedal. 4x at each corner and the pedal was rock-hard. Topped off the fluid, started the engine and the pedal felt great boosted. Cleaned it all up and left it on the lift overnight.

This morning I wrapped up installing the line brackets and cleaned up the mess from all the brake bleeding. Installed a few other items while it was still on the lift (gas & clutch pedal boots). Dropped the lift, hopped in and took it for a drive up and down the street. Made some minor prop valve adjustments and grabbed my wallet. Went for a 30 minute drive and man, the brakes feel great! Might need to make another small adjustment, but amazed at how well the disc brake setup is.

Should also note that the front steering is greatly improved with the kingpin replacements. New Warn hubs work great and the twin-stick is engaging the front axle. Overall, a great outcome for 'simple' projects

I've got a pretty big dad-do list for tomorrow, but I plan on pulling the MC piston out to see if there is any visible damage.

Thank you for all of the help, suggestions & humor! Greatly appreciated!

Next up, power steering (although after driving with good brakes, the lift kit (with new shocks) might be the the smarter project to undertake next).

 

[jscheier]

This might explain it best.

http://[URL]https://www.cnbrakecylinder.com/can-a-master-cylinder-fail-without-leaking-full-guide/

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So... when I was testing the old (but new) MC on the car, there was a significant amount of fluid movement in both front and rear reservoirs. With the issue seemingly relegated to the front reservoir (rear brakes), I wonder if that movement was from the bypass. The new Wilwood MC has minimal to no visible fluid movement when working the pedal.

 

[jscheier]

Sooooo..... I pulled the piston out of the first MC this morning. Looks like there was a bunch of debris in the cylinder (magnet would not pick it up, so I'm going to assume aluminum from the casting & machining process). Some light scoring of the piston, seal, and cylinder as well. I didn't take any photos (too much brake fluid everywhere. I see it in my dreams). I have packed it up and will be shipping it back to the vendor for them to inspect. I'm not expecting much in return.

I gotta say, man, these brakes feel awesome!

 

[SLOWnEASY]

Glad you got it worked out. That sucks about the machining debris. But at least now you know what caused the issue and that it wasn't caused by something you did or did not do.