I have an interesting problem. I think I have the wrong vacuum booster in my 87 4x4 Pickup... I can't find any writing or numbers on it except:
"Bendix License
Master Vac
JKC or JKO"

Talking to NAPA, they could not imagine that a Bendix booster would be used on anything as small as a Toyota 4x4. And what he described to me an oversized booster would do to my brakes is what my brakes do... Very easy (soft) pedal that grabs and locks the brakes really easy. I have been chasing brake problems on this truck since I got it (about 2 years). I have replaced almost everything except booster, portioning valve and lines... I have replaced all the hardware in the wheels. When I was checking out the master cylinder the push rod was cranked all the way in so tight I was afraid it was going to sheer off when I tried to adjust it. Who ever worked on this truck really messed it up!

Has anyone ever seen a Bendix booster on one of these little trucks?

Does anyone know where I can find the numbers on this Bendix booster to see what the proper application of this booster is supposed to be?

I'll take any help I can get on this,

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I wonder if that booster is intended to work with the larger bore master cyls like on V6 trucks.
I read that if you change to the larger bore master without the larger booster the brakes become harder to push.
Sounds like you have the opposite problem. Do you know which master you have? I believe they are marked with the bore size cast in it.

 

I had to replace the master because the one that came with the truck was faulty, had no rear brakes at all after a complete rear axle rebuild, hand priming the master just in case and setting the push rod. So the master I have is what Oreilly's version of what is supposed to be on there...

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I happen to think of where i could get the information. Both the current MC and the one I replaced are 13/16. The original was an asian with "R" and the number "52" on it.

The new questionable MC has 13/16 and "R" on it.

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It is a Toyota I have seen very interesting Repairs?? over the years.

As long as the (part?) repair gets the vehicle up and running or able to move under it`s own power all is good

Booster failure in the middle of No Where ! Correct part a week or better away !! This here should work been sitting here for years .

Installed and on the way till you need to replace it .

Decide what year you want get a Booster and Master Cylinder to match would no doubt be the quickest hunting for a unknown booster as you are seeing