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Old 05-30-2013, 07:13 PM
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Rezarf Rezarf is offline
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Default FJ40 Brake Booster Options?

So, my pedal has been getting squishy as I sit at a stop light. It has a really slow leak that begins to drop the pedal to the floor slowly and steadily. If I can sit there long enough the brakes start to lose grip... pump a quick half pump and they are tight again... booster right? Its been more noticeable since it has become hot.

I haven't lost a drop of fluid and during normal driving it brakes straight and quickly.

I have a mini-truck booster in there now, but I was wondering what might be my best option for performance? I am most likely going to do the rear disk swap with a proportioning valve as I have slowly collected a lot of the parts over the past few years since running the trailer.

Can I use an 80 booster? Any other good/available options? Treeroot, did you just do this conversion? Was it plug and play or was there any fab work?

Thanks!
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My rig... "Maude"
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Old 05-30-2013, 07:21 PM
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I run a 3rd gen 4runner booster out of the junk yard. It is a bit larger diameter and covers one of the mounting bolts for the clutch slave - but it works great. I have disc brakes all around. I believe a booster is a booster. It is the brake master where things get to be important with regards to disc brakes and propotioning valves.

If the mini truck booster has served you well, get. A new one to replace it, install it and run it.
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Last edited by RicardoJM; 05-30-2013 at 08:36 PM.
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Old 05-30-2013, 07:46 PM
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I've got an extra mini-truck booster taking up space in my garage. I pulled two when I had to replace mine so I didn't have to go back. If you want it, let me know.
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Old 05-30-2013, 09:19 PM
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I've run the Geo Metro conversion in the past with 32's, discs up front, and drums in the rear. Now the rig is SOA, has 35's, discs x4, and a proportioning valve installed but I haven't run it down the road yet. The BB is very compact & fits nicely but I'm curious about the stopping power with all the recent upgrades. Seems like Ricardo's suggestion would be the easiest, especially if it had adequate stopping power when working proficiently....
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Old 05-30-2013, 10:00 PM
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treeroot used an 80 booster in his 40 and seemed to be very happy with the result.

http://www.risingsun4x4club.org/foru...t=18565&page=3
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Old 05-31-2013, 07:09 AM
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I am running disk brakes on all fours, an 80 series master, and a booster from an 82 Celica. Backing spacer is from a minitruck. I had to go with the smaller diameter booster from the Celica because of space issues on the firewall of the early '73 fj40. I had to make no adjustments to the push rod.
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Old 05-31-2013, 09:07 AM
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Quote:
Originally Posted by Rezarf View Post
So, my pedal has been getting squishy as I sit at a stop light. It has a really slow leak that begins to drop the pedal to the floor slowly and steadily. If I can sit there long enough the brakes start to lose grip... pump a quick half pump and they are tight again... booster right? Its been more noticeable since it has become hot.

I haven't lost a drop of fluid and during normal driving it brakes straight and quickly.

I have a mini-truck booster in there now, but I was wondering what might be my best option for performance? I am most likely going to do the rear disk swap with a proportioning valve as I have slowly collected a lot of the parts over the past few years since running the trailer.

Can I use an 80 booster? Any other good/available options? Treeroot, did you just do this conversion? Was it plug and play or was there any fab work?

Thanks!
You don't need a booster, you need a master that isn't leaking past the piston seal. Just because it isn't leaking to the outside world doesn't mean it isn't leaking inside. The symptom you wrote about has nothing to do with how well the booster is working, in fact it sounds like your booster is fine, but your master is leaking inside.
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  #8  
Old 05-31-2013, 03:33 PM
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Default I'll agree with what Zepp said

I had this exact thing happen with my 40. I thought it was the booster...it was, in fact, the master. IMHO I'd start with that...
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Old 05-31-2013, 11:34 PM
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Well, that's an easy fix with new seals right? I think I rebuilt my master back in the days when I first got it.
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Rezarf <><
My rig... "Maude"
1976 FJ40 with some stuff and some leaks.

2001 Sequoia Limited with heated seats

My camping trailer build up thread.

"You 80 guys are just a Sawzall away from nirvana." -Red Chili
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Old 06-01-2013, 05:43 AM
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If you hone the bore of the cylinder, the seals will work better and last longer.
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