FJ80 (3FE) brake booster replacement question (1 Viewer)

[ashooter]

Anybody know if you can replace the brake booster WITHOUT disconnecting the hard brake lines from the master cylinder?

I watched the OTRAMM youtube video on replacing booster in an FZJ80... Looks like my FJ80 has more room to maneuver, but I don't want to break/crack a brake line trying to move the master cyl out of the way. Not sure how much flex I have to work with, so if anybody has experience, your input will be greatly appreciated!

 

[Rusty Marlin]

I did this job last fall without removing the hard lines, it's a little tight, as shown in the video from OTRAMM; but worked fine. Helps to have another set of hands when putting the new one in through the firewall.

 

[LC1979]

I also did this about eight years ago. I don't remember it taking but 20 minutes to complete. I did not remove the hard lines from the master cylinder. I think i disconnected everything needed under the dash, unbolted master cylinder and moved booster up and out.

 

[ashooter]

I also did this about eight years ago. I don't remember it taking but 20 minutes to complete. I did not remove the hard lines from the master cylinder. I think i disconnected everything needed under the dash, unbolted master cylinder and moved booster up and out.

FJ80 with 3FE... or FZJ80?

 

[LC1979]

FJ80 with 3FE... or FZJ80?

92 3fe FJ80

 

[SaturnAscends]

Check out Timmy the Toolman’s brake booster video. They manage to move the master cylinder and brake lines out of the way without taking them out. That’s on a 94 though, so I’m not sure if it’d be any different on a 3FE truck.

 

[Kernal]

I did this a few months ago (well almost) but the question about moving the Master cylinder is yes, you can gently pull it forward and slightly toward the intake just a bit, enough to get the old booster out and the new booster in.

IME however it was also a very tight fit getting the booster in and out past the intake manifold (FZJ80).

My attempt failed however as I was out of town trying to do this in a hotel parking lot and could not get the four booster studs through the holes in the firewall by myself.

So assuming the brake booster and brake pedal bracket are similar in the FJ80 and the FZJ80, this is what I found:

The reason that the booster studs would not go through the firewall holes is due to the bracket for the brake pedal assembly/arm which bolts up to the cabin side of the firewall. It uses the same four holes as the brake booster studs so if those eight holes are not lined up it is impossible to get the booster studs through, IME.

The fix as mentioned above is to have someone inside the cabin pushing on the brake pedal bracket to keep the four holes in it lined up with the four holes in the firewall. That should allow the four studs on the brake booster to go through both the firewall and the bracket. It's a very tight fit for the studs, there's almost no slop between the booster studs and the holes in the firewall.

Having said all that and after watching the videos on you tubby myself, no one mentions what I found in their videos (having to line up the brake pedal bracket holes with the firewall holes). They either skip over that part or just wiggle the booster until they get lucky and studs go through, likely because their brake pedal bracket is still lined up with the holes in the firewall and didn't slip out of place when the booster was removed.

FWIW

 

[rghouse]

just did this on my 92 3FE. yes it is no problem at all without disconnecting hard lines, and disrupting fluid. Just make sure and adjust the pedal arm under the dash to the stock placement. Unless you want different brake travel

 

[Godwin]

Whenever I replace a master cylinder or booster I always pull the MC because I want to take the time to check the booster push rod depth. Sometimes it needs no adjustment but often it does. This cheap tool makes checking and testing the adjustment easy Power Brake Booster Tool - https://www.classicchevy.com/power-brake-booster-tool-57-397920-1.html?adpos=1o5&scid=scplp57-397920-1&sc_intid=57-397920-1&gclsrc=aw.ds

 

[BILT4ME]

Whenever I replace a master cylinder or booster I always pull the MC because I want to take the time to check the booster push rod depth. Sometimes it needs no adjustment but often it does. This cheap tool makes checking and testing the adjustment easy Power Brake Booster Tool - https://www.classicchevy.com/power-brake-booster-tool-57-397920-1.html?adpos=1o5&scid=scplp57-397920-1&sc_intid=57-397920-1&gclsrc=aw.ds

I couldn't find that when I was going to do mine (and I was too stupid to realize I needed it) and apparently I wasn't searching by the right name or something.

Thank you for providing this tidbit!