Hello gents. I'm going to post this in the 67' - 72' forum as well but I want to do so here since it is topical.

I have a 72 F250 with power assist brakes. Disc front and drum rear. The Master cylinder went bad. I replaced the master ( I didn't bench bleed the master as I didn't have a vise big enough to secure it ) The truck also has a trailer brake system and this has a line running from the resevoir for the rear brakes ( brass fitting w/ 2 outlets ) to the switch box in the cab.

I bolted the master on and hooked up all the lines and proceeded to bleed all four wheels hence, bleeding the master in the process. Or so I think? The only line I didn't bleed is the trailer brake line as I couldn't find anywhere to bleed it ( no bleeder screw? ).

The brakes work but the pedal does not come back all the way and when applied the pedal is almost to the floor.

One thing I noted when doing the bleeding was the rear resevoir would actually " geyser " fluid up when the brake was pumped. The front resevoir did not do this.

I went through bleeding all four wheels 3 times in this sequence: Right rear, left rear, right front, left front.

So my questions are ,

Should I disconnect the lines and try to bleed just the master and then go through all the lines again?

Should I just disconnect the trailer brake line and plug the port?

Should I try bleeding the trailer brake line by unscrewing the end that goes into the switch box? ( messy ).

I'm thinking the trailer line is the culprit but since I didn't bench bleed the master and it is doing that geyser thing maybe that is the problem.

Considering the pedal is so lame I'm wondering if that 3 foot line from the rear resevoir to the trailer brake box is really an issue? I know it really should be bled, it's just odd how there isn't a bleeder screw.

FWIW, The trailer brake switch box has a **** on it that moves left to right when the brake pedal is depressed and it does do it now.

 

If you don't use the trailer brake controller I'd plug the line. You should have the geyser in both reservoirs, sometimes its hard to see unless the fluid level is low.

 

Thanks Bashby. I am going to try that. I was hoping for more responses figuring someone could I.D. what is probably going on.

To add to my explanation: I took out all the bleeder screws and wire wheeled them and cleaned out the drain holes. I also pulled out the lines from the master to the proportioning block? and snaked those.

I really need to get this truck back on the road since, ironically my brakes in my daily driver went out last week. I know that is not going to be a simple fix as I have already determined it isn't something I can easily diagnose ( if at all ).

The weather here was crappy yesterday and more scheduled for today so I probably won't be working on it until Wednesday.

Thanks for any help you guys can provide.

My worst case scenario is the master I bought is bad which is really going to drive me to drink since when I got it I degreased the outside and cleaned it ( I kept all the plugs in ) and shot it with chrome paint. Looks real purdy. They probably won't take it back now if I need another one.