78 Bronco

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Broncobuster

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I have replaced the powerbooster, master cylinder, lines (all), wheel cylinders, calipers, and the proportioning valve. I bled with helper "working pedal", gravity, and with a vacuum bleeder, to the tune of 5 qts. of fluid. Put on another set of wheel cylinders, checked engine vacuum (20"), put on another master cyl., took to a garage. They bled it and said "$35 please.". The pads and shoes are new, so are the rotors and drums. I still can't "lock em up"! The pedal is mushy. It stops, but I know I should be able to get a stronger pedal with less effort. Any suggestions? What am I missing?

 

4xfan78

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When you replaced the brake lines did you put the little brass washers on the lines? should be 2 on each caliper. If so I would check all the joints and make sure they are tight.

 
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Broncobuster

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Did you manually adjust the rear shoes?
18808[/snapback]

Thank you for the reply. Yes I adjusted them to the point of drag, when spun by hand with tires off. Then I adjusted out more to the point that the rears would lock up (too far out), and the front wouldn't. I even adjusted the plunger on the booster to factory specs. It seems like I'm not getting enough line pressure

 
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Broncobuster

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When you replaced the brake lines did you put the little brass washers on the lines? should be 2 on each caliper. If so I would check all the joints and make sure they are tight.
18812[/snapback]

Thanks for the reply. Yes, I even tried two different thickness of washers. Ialso checked the attaching bolts to make sure that the through holes weren't obstructed.

 

RTM

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What about the front lines themselves?

 
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Broncobuster

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What about the front lines themselves?
18821[/snapback]

Replaced all lines. I ordered my proportioning valve from LMC Truck....it was supposed to be adjustable from 100-1000 psi, but I found no way to adjust the pressure.

 

texan79&96

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you might want to try upgrading, i found a really good write up about a guy with the same problem as you (i also have this problem with my 79). he discovered that for a 78 a powerbooster from a 2 or 4wd 78 f350 is a bolt in replacement,(79 you can only use 2wd) the master cylinder also routes the lines away from the motor and looks a little neater. the next part of the upgrade is steel braided lines for the lift so they wont expand. then you run big ford car calipers (78 thunderbird) these are also bolt in use the same pads as the d44, fit in 15 inch wheels, and have more clamping power than the dual piston dana 60 caliper (supposedly, i havent tried it yet) you do have to convert the plumbing using 3an fittings. this will make your breaks very strong to where fade is now an issue. run some slotted rotors and you should be locking up 35s all day long!! im also doing rear disc with the tsm kit soon i found some 85 el dorado calipers with all the parking brake stuff for $20 its gonna be sweet. i hope this helps let me know how it goes if ya try it.

 

BASE861

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Have you tried disconnecting the booster all together and running it? That will tell you if it's working. I put a larger bore master cylinder in my 79 Bronco to help cure the same problem and it did fine. I would definitely go for the rear disc conversion also. I did so on my current early bronco and it seems to be doing a lot better now. Make sure you adjust the brakes and bleed them before you tighten the e-brake just so there isn't anything pulling on the shoes when you fine tune them.

 
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Broncobuster

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you might want to try upgrading, i found a really good write up about a guy with the same problem as you (i also have this problem with my 79). he discovered that for a 78 a powerbooster from a 2 or 4wd 78 f350 is a bolt in replacement,(79 you can only use 2wd) the master cylinder also routes the lines away from the motor and looks a little neater. the next part of the upgrade is steel braided lines for the lift so they wont expand. then you run big ford car calipers (78 thunderbird) these are also bolt in use the same pads as the d44, fit in 15 inch wheels, and have more clamping power than the dual piston dana 60 caliper (supposedly, i havent tried it yet) you do have to convert the plumbing using 3an fittings. this will make your breaks very strong to where fade is now an issue. run some slotted rotors and you should be locking up 35s all day long!! im also doing rear disc with the tsm kit soon i found some 85 el dorado calipers with all the parking brake stuff for $20 its gonna be sweet. i hope this helps let me know how it goes if ya try it.
18825[/snapback]

Yeah, I figure I'm going to upgrade. Are you saying to use the powerbooster AND the cyl. from the F-350 as a pair?

 
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Broncobuster

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Have you tried disconnecting the booster all together and running it? That will tell you if it's working. I put a larger bore master cylinder in my 79 Bronco to help cure the same problem and it did fine. I would definitely go for the rear disc conversion also. I did so on my current early bronco and it seems to be doing a lot better now. Make sure you adjust the brakes and bleed them before you tighten the e-brake just so there isn't anything pulling on the shoes when you fine tune them.
18841[/snapback]

Larger bore? Do you have a part # or is this from F-350 as above?

 

texan79&96

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yeah you have to use the matching master cylinder its only $15 at orileys. i can get you the part number tommorrow.

 
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Broncobuster

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yeah you have to use the matching master cylinder its only $15 at orileys. i can get you the part number tommorrow.
19106[/snapback]

Good enough. Thanks! I'll get the pair and give it a whirl, before I get the rear disc set-up, etc.

 

Broncoholics

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I'm sure you did this but did you bleed the master cylinder? You have to crack the lines where they enter the master cylinder as air can get caught in there when replacing with a new unit.

 
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Broncobuster

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Hey! guys....I found the prob. They just printed an article in 4wheel & off road that reminded me to put it in here.

I had to pull the pin on the prop. valve, then bleed....works like new.

Thanks again for the tips. Disc. mods coming after body work.

 
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