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Discussion Starter #1
Ok, here is my brake problem. I have a 69 FJ55 that has a chevy 350 and a holley carb. I am now on my second booster and can't seem to get much power assist. The other really troubling problem is that sometimes I have great brakes, without assit and other times I get no brakes at all also with no assit. Like on Tuseday I pull my truck out of the driveway and have no brakes, pedal goes all the way to the floor. Back into the driveway and good brakes. Go back out to the street and around the block nice and slow good solid braking with no assist. Then stomp on them and get a small fron end lock up.

The truck has 36" tires on a dana 44 front with disks and a dana 60 rear with drums. I have replaced all the brake parts and ran all new hard lines and new braided at the ends. Any ideas would be greatly appreciated I am stumped. Thanks
 

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I might be wrong but if you have no booster assist, the you would have a very hard pedal and you will have to push the crap out of the pedal to stop(this is what my fj80 did when the booster went out) if assit is working it will be softer pedal and will be easier to get braking.

maybe the check valve on(or by) the booster is not working.

John H
 

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Bleed ,bleed and rebleed. And the vacuum check valve as landpimp said. Are you getting good vacuum to the booster? Just asking, but did you bench bleed the MC before you installed it?
 

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sounds like you have two problems, #1 your master cylinder sounds like it is crapping out, #2 your power assist has problems.

The dying master cylinder is the more critical of the two obviously.
 

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Discussion Starter #6
I did bench bleed the master prior to using it and it was new along with the booster. I am using a master I bought from a Hod Rod shop online so I don't know what it orignaly came from. I now have a junk yard booster from a mid 80's Suburban and the master bolted right up indicating the master is a chevy product??

I do have two problems but would really like to solve atleast why the brakes sometimes work and sometimes don't. I will check the vaccum to see if I can get some assist but what really troubles me is why sometimes I have great, no power assit brakes and other times the pedal goes al the way to the floor with no resiatance at all. Thanks for all the help.
 

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calfj60 said:
I did bench bleed the master prior to using it and it was new along with the booster. I am using a master I bought from a Hod Rod shop online so I don't know what it orignaly came from. I now have a junk yard booster from a mid 80's Suburban and the master bolted right up indicating the master is a chevy product??

I do have two problems but would really like to solve atleast why the brakes sometimes work and sometimes don't. I will check the vaccum to see if I can get some assist but what really troubles me is why sometimes I have great, no power assit brakes and other times the pedal goes al the way to the floor with no resiatance at all. Thanks for all the help.
Guestion? why are you running the unknown Chevy(or whatever) master booster?

I would think unless your running something other than Cruiser brakes/axles(and this I don't think really matters) then you would be best running a Cruiser(or other Toyota) master/booster. The motor really doesn't have anything to do with the braking system AFAIK. I don;t know jack about chevy motor conversion maybe the Toyota master/booster doesn't fit and this is why you changed. I'm just thinking not trashin on you, as I'm not an expert

How about the push rod from the pedal to booster, then rod to the master if these are out of adjustment then this is gonna make the brakes do wierd stuff.

Seeing how the booster/master is new than more than likely this isn't the probem(unless they arn't matched to your brakes, but I don't know much about this)

Or there is air someplace and it needs to get blead out.

Just thinkin out loud :)

John H
 

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Discussion Starter #8
Thanks for all the ideas guys, please keep them coming. i really want to drive my truck again real soon. Can I buy a longer push rod for the booster to the M/C somewhere like Napa? Thanks and I will see if I can round up a buddy and try to bleed then brakes again tommorow or tuesday. thanks Tim
 
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