Options for master cylinder replacement.

[archie73]

So both master cylinders are leaking into the cab on my 73 40. The booster is making a hissing sound. I’ve converted to mini disc up front and rear discs are somewhere in the distant future. I understand the T100/fj80 brake master combo is a solid replacement. I’ve rebuilt masters in the pass, with not much success, so I’m wondering about the easiest/best performance upgrade on the master cylinders?

 

[ToyotaMatt]

Agreed , Rebuilding is a waist of time

 

[TimeIsMoney]

I have city racer's booster. Works great.

 

[bikersmurf]

JDM 80 Master and Booster with Toyota 4 piston Calipers in front and GM 3/4 ton brakes in back. It has a gobs of braking power to stair. It’ll stop a 4700 lb truck towing a 4000 lb trailer straight as an arrow with minimal pedal effort.

At 30mph, on dry pavement, it’ll easily lock all 4 10” wide wheels with the pressure of two fingers.

 

[cruiseroutfit]

We use one of the 80 Series cylinders for 4x/5x/6x/7x upgrades, they work quite well!

 

[C6H12O6]

Any hint as to which 80 MC? I'm guessing one of the non-ABS models, but even then, there are several. Wires off the cap? Off the bottom of the reservoir? Piston size? I'm stumped.

 

[cruiseroutfit]

I'm pretty sure our part# BKN60570, that would make it 47201-60570. I'd have to double check that tomorrow

 

[FJ40Jim]

So both master cylinders are leaking into the cab on my 73 40. The booster is making a hissing sound. I’ve converted to mini disc up front and rear discs are somewhere in the distant future. I understand the T100/fj80 brake master combo is a solid replacement. I’ve rebuilt masters in the pass, with not much success, so I’m wondering about the easiest/best performance upgrade on the master cylinders?

Both master cylinders are leaking?
Simply replace the clutch master w/ a1978 type and bend a new M10 Hardline to fit.

On the brake master there is not a performance upgrade available. There are different bore sizes available. The stock MC is 1" bore. Replace with any 1" master to keep the current pedal effort. To increase pedal effort use a 1-1/16" MC from a T100.
For decreased pedal effort, use a 15/16 or 7/8" MC from a mini or disc brake FJ40.

If the brake booster is hissing, check the pedal height, pedal freeplay and MC freeplay first. If nothing is holding pressure on the booster, then it needs replaced. There are many replacements available from later model Cruiser or minitruck.

HTH

So both master cylinders are leaking into the cab on my 73 40. The booster is making a hissing sound. I’ve converted to mini disc up front and rear discs are somewhere in the distant future. I understand the T100/fj80 brake master combo is a solid replacement. I’ve rebuilt masters in the pass, with not much success, so I’m wondering about the easiest/best performance upgrade on the master cylinders?

 

[toyotaspeed90]

Larger bore will shorten the pedal throw, but lower the pressure in the system. Smaller bore will increase pressure in the system but will require a longer throw in the pedal.

In the performance/racing world, it's a fine line - but generally most people like a shorter throw and go with a larger bore MC.

Whatever you do - replace it with an aluminum master. Usually rebuilds fail, on cast units, because moisture in the fluid pits the bore of the master cylinder, and fluid gets trapped in the pits when pressure is being applied, and will stay behind the seal when the pedal comes back - eventually dumping into the booster/cab of the vehicle.

I have a supercharged Previa master with a non ABS SW20 (2nd gen MR2) booster, and it works for my setup just fine.

 

[archie73]

Not to sound wimpy, but I’m looking for best performance with an eye toward ease of installation. The rest of the truck needs attention, so if there’s an easy button on this I’d appreciate it.
For the clutch master- sounds like a 78 fj40 master is what I want. Will this play nice with the Chevy clutch(350/sm465-stock Toyota slavecombo)?

 

[FJ40Jim]

Brake 'performance' is not well defined. If higher effort & shorter travel is desired, go bigger. If current config is good, stay the same size. If lower effort & longer travel is desired, go smaller. For ease of installation, look for a Toyota 4-bolt MC that has the same line orientation as what's on there now.

No, the later clutch MC will not work as well as the current early clutch MC. The Chevy setup requires a longer throw and the high volume early MC is just enough. Changing to the smaller bore later MC will probably not give enough travel at the clutch fork without also changing the slave cylinder to a later type.

 

[toyotaspeed90]

I had a 76 master bolted to the MR2 booster (same bolt pattern) and then replaced it with the (used) aluminum Previa master cylinder - which really only required some bending of the lines. The lines were already not original, but they were originally created for the 76 master.

 

[C6H12O6]

Sorry to hijack, but let me throw a question out there that seems to be related. My drum/drum master on my '74 is shot. Trying to get the truck up and running, and need a master to get this thing moving. A disc brake upgrade is on the short list, and I was looking at one of the non-ABS 80 masters. I'm wondering if this new disc/drum master will work for the current drum/drum setup for a few months until I can sort out the rest of the disc upgrade stuff.

Can I run the disc master with the old drum booster?

If I replace the booster and master together, can I still run the new disc/drum MC+Booster with the drums up front for a while?

 

[FJ40Jim]

The 80 MC is 1" bore, so it will feel/work the same as the stock 1" bore MC.

The new MC will bolt to the original booster, but pushrod depth is slightly different on the 80 master, which will require grinding about .100" off the booster pushrod.

HTH

 

[C6H12O6]

Thanks, Jim.

If this is all it takes to make the stock booster work, is it still necessary to go to a dual diaphragm booster if only running front discs?

 

[FJ40Jim]

It's not necessary to change the booster, but the early booster does not have as much assist as the disc booster, so expect to use a little more leg power for serious stopping with the discs.

Anecdotal data: my FJ45 has front disc swap with bigger 4runner front calipers, and the common GM RDB swap, with cheap, aggressive pads on both axles. It stops OK with a 1" MC and no booster. A smaller MC or a power booster would decrease pedal effort further, but I can live with the current config indefinitely.

 

[archie73]

No, the later clutch MC will not work as well as the current early clutch MC. The Chevy setup requires a longer throw and the high volume early MC is just enough. Changing to the smaller bore later MC will probably not give enough travel at the clutch fork without also changing the slave cylinder to a later type.

I should of asked this earlier- part of my thought was to get a clutch off a newer application for availability down the road. I’m 90% happy with the stock setup, but if there is a newer application that’s a oem I’d prefer that. Aftermarket parts have less interest to me. So has anyone found an easy bolt up clutch master cylinder from another car or truck?

 

[FJ40Jim]

The 75-85 FJ40/60 slave is common & reasonably priced. Aisin CRT012 is $18 at rockauto.

The 75-80 master is also pretty common, and is an easy retrofit to all earlier FJ4x and FJ5x, so it continues to have good availability.

 

[roadstr6]

If you use an early 80 series brake master (disc/drum) on a four wheel drum truck, you will likely need to plumb a residual valve into the front circuit. If you don't, you'll have to double pump the brakes to get the drum fronts working. Drums need that 3psi residual to hold the pressure.

 

[FJ40Jim]

The FJ80 1" MC does not have an RPV in either outlet, so it might be more economical to get a '74 or ' 75 1" MC with RPV in both outlets, if RPV is desired.