So, I have changed all my lines, proportioning valve, calipers, drums, solenoids, booster, and master cylinder.

1977 F150 4x4

The brake pedal goes to the floor easily, too easily in my opinion. The brakes are working but seem really soft. Could it be a bad vacuum?

 

Assuming the MC was bled prior to installation, next easy step would be to measure the rod gap per the attached PDF.

 

sounds like your not done bleeding if you replaced everything chances are you still have air in the system

 

Are the rear brakes adjusted properly?

If you pump the pedal a few times quickly, does the pedal firm up?

 

I'll be checking this here in a bit!

 

Did you bench bleed the new MC before mounting it?

 

I did not, was going to but didn't have the old lines that matched up

 

Maybe I am an a$$ but you replaced "everything" good to know. I can go after this at many angles. First of all asking for help on a forum information is key and details are helpful. the more the merrier. Does the system have fluid? Refilling was never mentioned and/or confirmed. Is the system with proper fluid properly distributing fluid to all areas of brake circuit? Is there a brake controller involved and if so is it happen to be plumped into brake fluid circuit with fittings and additional lines? Are calipers properly sliding back and forth within caliper anchors? Is the engine holding steady vacuum? Remember folks, these brake boosters utilize only 2 cylinders primarily in order to feed vacuum to booster, and if booster happens bad, those cylinders lean out and if master bad then suck brake fluid and now 2 weak cylinders; furthermore vacuum will deteriorate and'/or even be non existent. I know. I just worked on this exact issue within the last month on a 1977 4x4 f150. No brakes. I believe it was an engine problem primarily. I was deemed stupid and all brake system parts went in trash and replaced... no change. Engine came apart and had 2 cylinders totally burnt valves; one on each bank. You can imagine my reaction and I now will no longer attempt to help this self proclaimed genius. After verifying/confirming these issues, Follow up and I will provide another list of DIY checks to attempt to narrow this problem down.

 

Wow! actually makes me a little happier that someone else has gone down the same road I am on. Let me see if I can answer the questions.

1977 F150 4x4,
ALL lines, calipers, pads, shoes, drums, solenoids, proportioning valve, master cylinder, booster REPLACED
I did not bench bleed the Master but, I did bleed the brakes with a bleed kit and I did get fluid from all four corners.
Bleeding starting points were as follows: rear passenger, rear driver, front passenger, front driver
I made sure the master never went dry or below the line holes and I filled it up after the bleed was what I thought to be complete
I also measured the plunger rod off the old booster and matched that to the new one.

You mentioned having a vacuum issue on yours and I am wondering if the vacuum on mine could also be less than what I need. I do not think the valves are bad or anything like that but I do think there is a possibility the vacuum is not hooked up correctly. This truck has had some "work" done to it in the engine bay (not by me) and I am fixing all of that now so it could be a bad vacuum.

Anyway, I really do appreciate all the help and support here in the forum guys so please keep it comin.

 

I think the big issues was not bench bleeding the master before bolting it to the truck.

My system was open for years as I rebuilt my truck.
I was using a used booster and master off a parts truck that "I thought" was good as the truck was being used when it rolled on to its roof.
Well I did nave issues trying to bleed the system but the problem really showed up on the first test drive......NO BRAKES!
Booster you could now hear leaking and the master went to the floor! None of this showed up in the garage or moving it in & out.

Got a booster and master cobo from the local parts store. It also had issues when bleeding, had a pedal but not really good but it stopped.
I had to replace the rear Ebrake cables as they were the wrong ones installed and when I got it back together brake pedal went to the floor!
I did nothing to the system that would have caused this. Tried to bleed the system and still vary low pedal?
I bought a new master, bench bleed and installed and got the best brake pedal the truck ever had.

BTW I was using a pressure bleeding system when bleeding the system each time after the 2 man bleeding did not work.
Yes I had fluid coming out at each wheel, no air, but a bad, low or no pedal at all till the 2nd new master.

With today's parts don't over look a "new part" being any good as lot are bad out of the box.
Dave ----

 

So, I'm not a brake guy and this question might be a dumb one.

If you don't bench bleed the master but bleed the system from each corner as you normally would, doesn't that mean the fluid is flowing as it should through the master?

 

That's a good question.

Yes, the fluid will flow, as you've observed, but if the MC wasn't bled, air could be trapped in it.

Same principle as bleeding the brakes.

MC needs bleeding as the very first job.

 

Measure the actual gap.

 

Going to borrow a digital caliper today

 

If you bleed brakes with a in use brake system, chances are the MC is full of brake fluid. If you are bleeding brakes after a new MC was installed, as you pump fluid through the lines, you also pump the air that was in the MC when it was made / rebuilt. You don't bleed brakes just to get fluid through, you bleed brakes until NO air comes through. Up at the new not yet bench blead master, you might be pushing fluid, but you are also pushing air bubbles that will continuously try to float back up, to be pushed into the line again. Brakes do not work on flowing fluid, they work using trapped fluid that is compressed, and any air in that fluid is far more compressible than fluid, so you get soft pedals at the floor or just a pedal on the floor.