The Stovebolt Site Forums The Shop Area Driveline Brake bleeding

Can't seem to get a hard pedal after pumping the pedal. Get a few drops of fluid coming thru the hose. Set up is disc front, drums rear, prop valve, master cylinder and booster under cab floor. Have a #10 residual pressure valve to the rear and a #2 valve going to the front.

Some proportioning valves have a special tool that disables them for bleeding. It also helps if you bench bleed the MC before you put it in. I'm guessing the air bubbles are having a hard time getting past the proportioning valve.

What kind of tool 4 on the floor?

Just curious....what type of proportioning valve are you running? Was it part of a kit that came with a master cylinder/booster? Was it a salvage component? Some prop valves have an internal pressure differential valve that has to be centered before you can bleed properly. Some have a little knob that you use a notched tool to pull out when bleeding.

I ran into the same problem when trying to bleed the system with a salvage m/c and (multi-line) valve....now I use the Wilwood Adjustable proportioning valve from Summit Racing ($39.00) on the rear circuit. It has an "in" and an "out" and I can regulate my rear brake bias as well as bleed without problems.

There is a lot of good brake info on the following sites:

http://www.ecihotrodbrakes.com
http://www.mpbrakes.com
http://classicperform.com

Give us a little more info please.

Dave

It was a kit from JPL in Aliquippa, Pa. The residual valves are Willwood. Not sure about the master and booster. They put the parts together when we bought our TCI mustang II kit. The prop valve has a rubber cap on what I believe is an adjustment screw on the back of it. Haven't tried to adjust the prop valve though. No matter what method we try, we can't seem to get a hard pedal. Even went out and bought some of those speed bleeder valves. I think we may just pull the master cylinder off, and bench bleed it again and start over from the beginning.

I never pull a m/c to bench bleed. Simply crack the fitting with a rag underneath. 99% of the time gravity will make the bleed. If you have to, someone can push the pedal.

Here's a neat idea for a pressure bleeder, which can help with the difficult jobs.
http://www.myoldtruck.com/forums/showthread.php/homemade-brake-pressure-7011.html

Fred T, Which fitting should I crack loose if I don't remove the m/c. That is the way I would rather go than removing the m/c. Also, are you saying loosen the fitting, leave loose and bleed while the fitting is loose. My 75 corvette will gravity bleed with no problems. Didn't think the truck would gravity bleed because of the residual valves.

Not an expert by any means, but coulda swore ya needed more residual for discs than drums becasue you have the adjusters on drums where discs just float.

ANYway,... When I was puttin together my lil beast of a car, I had a similar issue. Turned out my master cyl just didn't have the volume to push the discs, so I never got a proper pedal feel untill I upgraded my M/C to something made for discs. If you were given a M/C with too small a bore that may be the issue.

What he's saying, if I read him correctly, is to loosen both the front and the rear fittings at the master cylinder (before they get to the residual valves). One thing you have to be sure of is that the master cylinder is level...you may need to loosen your mounting bolts and then I would tap on the M/C to dislodge any air bubbles that might be trapped inside. I wouldn't pump the M/C as it will suck air back in past the loose fittings....just let gravity and a few light taps do the work.

If that doesn't resolve the problem, you might be wise to pop it loose, put it into a vise (level) attach the bleeder hoses so they are under the fluid level and start back at step one. Either way, you're going to have to bleed the entire system as the fluid between your M/C and the residual valves will gravity drain out when you loosen the M/C fittings. Hope this helps.

Dave

Dave is on the right track. Yes, I meant the brake line fittings on the m/c. You should be able to loosen them and let a small amount of fluid flow out by gravity. Then tighten the fitting. Leveling the m/c is not required unless it sits at a horrible angle.

If the fluid doesn't flow, treat it just like a bleeder valve. Fill the reservoir. Have someone push down the pedal. Crack the fitting until the pedal is down, then tighten before the pedal is released. You should only have to do it once.

Thanks Fred will give it a try. Didn't work on it today, temps in the single digits. We use a kerosene heater, works only fair in these temperatures.

Thanks FredT and Dave. Got the brakes bleed today. Did what you guys said loosened the two lines at the M/C, let some fluid drain out . The rest was easy. Thanks again. Coach Frank