Brakes!!

Hey guys. Been a while since I've posted.  The brake saga continues.  To catch you up (fairly) quickly:

1986 F150 XL, 4X4, 300ci, 4spd manual, power brakes

Left rear wheel would slide on gravel when pushing in the clutch to shift at low speeds.
Rebuilt both rear drums - springs, shoes, wheel cylinders - all new parts.
Bled rear brakes (not the front since I never touched them).
Brake pedal was normally stiff during the bleeding process.
Started truck - brake pedal went to floor when pressed.
Bled rears again.  Same result.
Bled rears again.  Same result.
Truck sits in garage out of frustration for several months while I contemplate selling it.
Thought better of that a few weeks ago and...
Bled rears again.  Same result.  All air appeared to have left the lines every time I've bled the brakes.
I've probably ran a bottle and a half of brake fluid through the system now.

Per suggestions from a Bullnose page on Facebook - I probably need to bleed the fronts.  And get a new master cylinder.  I think I'm going to do this anyway but I though I would ask you guys since I trust you more.

Also, regarding the MC, the one I need is probably second from the bottom in the pic, right?


Screen_Shot_2022-06-07_at_8.png

It won't hurt to bleed the front brakes, but as it is separate in the system I don't think it will matter.  But I do think it is time for a new master cylinder.

I've included my own screen shot of that same Rock Auto page and included both the year/model info as well as all of the options.  And personally I'd go ACDelco unit at about half the price of that Dynamic Friction unit.

Just because the others don't say "4WD" they are.  Looking at the info on this site (Documentation/Driveline/Brakes) I see that an '86 takes the same master cylinder whether it is a 2wd or 4wd.  

Thanks, as always, Gary!!

I don't see in the list of work where the rubber brake lines were ever replaced. If you're going to do the MC and you don't know the last time the lines were replaced, I'd take the opportunity to do it. Old lines can swell internally and cut off the flow of brake fluid. That might mean that the fluid never reaches the calipers/cylinders, or that might mean that the pressure is trapped at the caliper/cylinder, making the brakes drag. Stainless braided hoses are a nice upgrade and not very expensive.

When I have to bleed the brakes, I get out the shop vac and some fittings so I can use shop-vac negative pressure to pull the fluid through. Works great!

I see you are in NE TX somewhere, so am I. If you're close enough I can bring the stuff over and help if you want. I'm in McKinney.

Pete -

I'm in Rowlett and I just may take you up on that.  

Gary Lewis wrote

It won't hurt to bleed the front brakes, but as it is separate in the system I don't think it will matter.  But I do think it is time for a new master cylinder.

I've included my own screen shot of that same Rock Auto page and included both the year/model info as well as all of the options.  And personally I'd go ACDelco unit at about half the price of that Dynamic Friction unit.

Just because the others don't say "4WD" they are.  Looking at the info on this site (Documentation/Driveline/Brakes) I see that an '86 takes the same master cylinder whether it is a 2wd or 4wd.  

Come on Gary have him bleed the rears again
I just went through this on my truck but lets back up a little.
When I got the truck on the road the master & booster I found were bad so they were replaced.
The new master was not good from the start as I was not happy how the pedal was.

I replaced the Ebrake cables and when I hit the pedal it went to the floor!
I did the bleeding front & rear a few times and still could not get the pedal off the floor
I bought a new, not a reman but new master, bench bleed and installed. I then did a pressure bleed the full system and the pedal has never been better.
I am with Gary replace the master.

Pete Whitstone wrote

I don't see in the list of work where the rubber brake lines were ever replaced. If you're going to do the MC and you don't know the last time the lines were replaced, I'd take the opportunity to do it. Old lines can swell internally and cut off the flow of brake fluid. That might mean that the fluid never reaches the calipers/cylinders, or that might mean that the pressure is trapped at the caliper/cylinder, making the brakes drag. Stainless braided hoses are a nice upgrade and not very expensive.

When I have to bleed the brakes, I get out the shop vac and some fittings so I can use shop-vac negative pressure to pull the fluid through. Works great!

I see you are in NE TX somewhere, so am I. If you're close enough I can bring the stuff over and help if you want. I'm in McKinney.

X2 what Pete said
Part of my 4 year truck rebuild was replace the rubber brake hoses.
Dave ----

Jmac1773 wrote

Pete -

I'm in Rowlett and I just may take you up on that.  

Just down the road! Be glad to help.