Thread: Brake bleeding....booster under floor

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I'm having just a bear of a time bleeding the air out of my '53 brake lines. It is a power brake booster and master cylinder under the floor in the stock location. I have been using different methods. Those being a mity-vac brake bleeder, and even pumped it with my foot and manually released the valve at the brake. However, I am not getting ANY air out of the system, well I was initially, but not anymore. Still, the pedal has that feel that there is just a bit of air in the lines.

I have disc brakes in the front, and drums in the rear with a proportioning valve and the proper check valves all plumbed inline. I just keep being told that these under floor models will take some work to get them right. Is that so? Maybe these brakes aren't supposed to feel like the "new" cars? The system is funcional, but doesn't have that "stop on a dime" feel like most any other car. Any tips/suggestions are welcome. I got my rebuilt tranny back in and I should be up and rolling finally by next week. Oh, also, my engine vacuum is about 13-14 so that shouldn't be a factor, I'm just throwing that out there if anybody is interested.

Did you bench bleed the master cylinder? If not, you can bleed till you own the brake fluid company and it may not have a hard feel to the pedal.

We bled 3 quarts of fluid thru the rock crawler Willwood system and it still didnt firm up till we bled the m/c......

if there is any air in the lines, after you pump up your brakes and then take you foot off of the pedal, wait a min. and mash the pedal down again, if the pedal goes way down then you have air. if they stay about the same place every time then there is no air. it could be the shoes just need to seat in.

I use a pressure bleeder, works best especially when the master cylinder is mounted below the level of the calipers.

i had a heck of a time also bleeding my brakes and getting the air out of them . finally made a little vacume bleeder the hooked onto the brake bleeder scew and it still took a long time to get the air out . seems to have something to do with the mast cyl lower than the brakes, or that you start with a dry syst.

Well, the pedal wouldn't return and I called the manufacturer said to install a pedal spring. That sort of burns me right there because of how much money I spent to begin with and they didn't even supply one, and I don't think I should have to use one....but none the less....I put one in, now it returns very nicely.

If I pump the brake (2-3 pushes) it will firm up. If I try it within a couple hours, it is almost as firm as it was before, probably within 85% of the firmness as it was the before.

I do have a vacuum bleeder, at least that is what I think the mity-vac does. It has just been sucking out clear fluid with no air.

Thanks for the links and suggestions and I'll keep you guys updated. If all goes right, I'll be taking it to the alignment shop next week.

Nothing worse than getting that first ride in a hot rod and having your tranny take a dump! That's what happened to me at the end of last summer. 16 miles and the tranny went bye-bye. I've been itching to start tweaking with all the little engine adjustments and such.... hopefully next week it will finally be on the road.

53 you shouldnt have to use one. most brake pedals don't come with a spring because it shouldn't need one to help pull the pedal back. if you bench bleed you master cylinder you know how hard the piston was to push in and that should be enough to push the pedal back up. if it want push it back up, then it sounds like your pedal might be to tight or the rod is adj. out to far or something. wouldn't hurt to check on that. most of the time the extra spring is for anti rattle or to take the play out of the pedal. but if i had to put a spring on mine to get my brakes right id find out why. the spring in the master cylinder should push it back.

Did you bench bleed the MC? If not then you should take it off and do that and refill it back up. Let it gravity bleed and then manually do it. You have the pressurized bleeder so that is even easier so do that instead of manually. They should work after that... If it still doesn't work then check for leaks on all the hoses and fittings, etc.

I just bled my under the floor booster too. For one thing, I took a bath in brake fluid while lying on the ground trying to get the thing in place after bench bleeding it. I guess I should have plugged the holes, but the level in the res. stayed high enough so that air didn't get back down in there anyway.

I was having trouble at first too, I was just pressing down on the pedal one time and holding it. The drums bled ok, but the discs weren't. Then I talked to an older guy and he told me to pump them 4 or 5 times and then hold it. That worked.

Under floor masters are a real B**ch,,,,rent yourself a pressure bleeder,,,,,and like everyone else is saying,,,,,bleed out the master first,,a quicky way to do this,,,have the wife or girl friend pump the pedal,,while you get underneath and crack the rear lines first,,then the fronts on the master cylinder,,,,tell the wife/girlfriend/buddy,,to really step down and hold it there,,,,you want to open the lines on the downstroke,,and then tighten before the upstroke.( you only have to do this for two strokes)
Also,,,,the proportioning valves also act as a pressure resevoir for the front discs,,(dont forget,,the fluid has to travel uphill before it reaches the front disc brakes,,it might be a good idea to open ahead of the proportioning valve on the downstroke too.),,,,,,,after you have bled the master cylinder,,,then attatch the pressure bleeder to the system and bleed away.
attach rubber hoses to the bleed nipples and route them into small pop bottles,,to save the fluid, ( warning!!! do not re-use afterbleed fluid for a period of 24 hours until all the airiation is gone) persistence pays off in the long run.

If you had to make a choice of these two $20 bleeders which one is better?

http://da.harborfreight.com/cpisearc...eder&Submit=Go

The MC on my 53 F100 is also under the floor. Although not power boosted, I bled it successfully with a "one man bleeder" that uses one clear plastic tube to the fluid cylinder and one in a jar with enough fluid in it to cover the end of the tube. You then just start at the farthest wheel, pump the pedal up, open the valve and let fluid out untill no bubbles, close valve and go to next farthest cyl. I believe it took two trips around, but worked well.

under the floor units are no differant than any other system,what system are you using? how big of a rotor? have you adjusted the rear brakes yet? if not this could be the problem with the mushy feel and brake pedal return.hope this helps .Tim

Realy the only way to do an under the floor is with a power bleeder There getting harder to find but worth the effort. Somehow I wound up with two Wagner power bleeder balls.

Originally Posted by 34fordcoupe

If you had to make a choice of these two $20 bleeders which one is better?

http://da.harborfreight.com/cpisearc...eder&Submit=Go

Im only asking about these cause I have tried using a clear silicone tube from the wheel cyl. into a cup, but this want work due to air being sucked back in around the bleeder nut. In other words a one man job.