Dual diaphragm brake booster install (1 Viewer)

[cheeese]

Hey Mud, this is a quick walk thru for installing the City Racer dual diaphragm brake booster in your FJ60. There's a posted installation guide for the FJ40, which serves as a general guide for the swap. OTRAMM also has a useful 80 series video on their channel. I'm doing this specific swap for the first time due to a failing OE booster— I'm not an expert. Chime in below if I've missed something or done something wrong

You'll need:

• ratchet with a U-joint, a short and medium extension, and 12 and deep 13mm sockets. Wobble sockets could be used if you have those
• Needle nose pliers or a pick for the spring cotter
• Screwdriver and adjustable wrench for the yoke and jam nut
• Pliers and the above wrench for the output acorn and jam nut
• 13mm offset combination wrench or ratcheting wrench if you don't have a deep 13mm
• Calipers (optional, but recommended)

Follow the steps in the above guides to remove the 4 12mm nuts holding the master to the booster, I also needed to remove a 12mm bolt on the firewall that retains 3 of the brake lines to allow for enough freedom to gently flex the master toward the front of the truck. Then go into the driver's footwell area and locate the connection between the pedal and the booster input rod:

Remove the spring cotter, then push the connecting pin out of the yoke. The booster can now be removed from the firewall. Measure the distance between the firewall mounting surface and the yoke-jam nut interface, in this case mine was 4 1/2". Transfer the existing yoke to the new booster and set it at the same measurement. The City Racer booster is supplied with a spacer, but on the 60 it doesn't appear to be required, nor is there enough input rod to reach the matching measurement. I removed it.

Next you'll need to adjust the booster output rod to master interface. Appendix 2 and 3 in the City Racer install guide lists procedures to do this. I opted to use a digital caliper and method 3. The critical dimension is the booster/master mounting surface to the tip of the booster rod, which must have 0.1–0.5mm of clearance to the master input piston.

First measure the max depth of the input piston to the extended nose on the master:

Then the distance between the mounting flange and the extension:

Subtract the second measurement from the first to get the rod extension. In my case it was 8.6mm. Then I adjusted the booster output rod to be 8.7–9.1mm from the mounting surface of the booster. To minimize slop in the brake pedal, try to keep the measurement closer to the low end of the tolerance spec.

 

[cheeese]

Now you're ready to install the new booster. I transferred the heat shield from my old booster and realized the arrangement of the 4 mounting holes and input bellows meant the new booster installed with the vac connection 180º from the old booster. Note the center hole is closer to the top two holes than the bottom two. Ensure when you dry fit the booster against the firewall that the yoke fits over the brake pedal, the pedal connecting pin fits in its place without depressing the input rod, and the brake light switch operates correctly— if the yoke is too far down on the rod, the brake lights will be on in rest position. The switch itself is adjustable if you need to tweak this, but I adjusted the yoke position on the input rod until the pedal sat softly against the stop. Remember to re-tighten the jam nut.

The new mount hardware is 13mm rather than 12mm, but otherwise it installs the reverse of removal. You might need a deep socket due to the longer studs on the new booster. I used a combination wrench.

Note on the vac routing on the new vs old booster: the guides say to install in the same orientation as the old one, but there's only one orientation of this part where the studs and input bellows will align with the holes in the firewall. So if you have the arrangement shown on the right, you can delete the U-shaped pipe that loops below the master and connect the main vacuum line directly to the check valve on the left. On my truck that vac hose is quite stiff and is taking a lot of gentle persuasion to fit over the plastic vac nipple.

Once that's connected, gently guide the master back into position and reinstall on the booster. If you're using adjustment method 1, or if you want to double-check your output rod clearance, now is a good time to have a helper press on the pedal while you hold the master in place. If you immediately feel the booster move, you need to shorten the rod by 1/4 turn or more. Remember to re-tighten the jam nut if you adjust the output rod.

When you're satisfied with everything, reinstall the four 12mm nuts for the master, and gently work the brake lines back into their original positions. If you removed the firewall retainer, reinstall its 12mm bolt. You're almost done!

As with any brake service, take extra care during the first run in case something isn't right. In this case you haven't opened any of the hydraulics, so as long as the mechanical connections between the pedal, booster, and master are correct and tight, you will at least have some brakes. But keep a hand on your emergency brake anyway

Hope this is helpful if you're considering this part for your 60

 

[SteveH]

Any thoughts on how well it works, or if it's mower powerful than stock?

 

[cheeese]

Technically without altering any hydraulic components, the actual braking force and proportion thereof is unchanged. However, the pedal force required to apply that force is definitely less. On a test drive the new one feels like it has improved modulation as well. Partly this is comparing from my old booster leaking vacuum and not functioning as designed.

 

[4runner2FJ60]

Older thread, but I am now confident my booster has not been installed upside down for over 2 years! My rig came without working brakes or booster, so it is hard to compare to anything, but the brakes have been very grabby at times and can lock up if needed. I have the stock side master with 4runner front calipers and am very happy. Is the grabby feel a possible mis-adjustment of the booster rod length? I have had no leaks or issues other than the passenger shoe getting over adjusted. I performed the fix in one of these threads. Thanks!