1973 Master cylinder (1 Viewer)

[cruiserguysc]

My 73 fj40 break master cylinder has failed. I’m planning on converting the front from drum to disc. Should I go ahead and replace MC with mini truck MC since I plan on eventually doing the conversion?

Recommendations? Thanks

 

[charliemeyer007]

Put a kit in it for now. Start Kroil all your fittings now. $50

 

[pb4ugo]

I think the later model m/c has a smaller piston diameter for discs brakes and may not work properly for four wheel drums. I think drum brakes uses a larger 1" cylinder. You might consider rebuilding yours to get thru until you make the brake swap. Are you going to be swapping to Toyota disc? That might make a difference too. Im pretty sure @cruiseroutfit has rebuild kits and can answer any questions.

 

[cruiseroutfit]

I think the later model m/c has a smaller piston diameter for discs brakes and may not work properly for four wheel drums. I think drum brakes uses a larger 1" cylinder. You might consider rebuilding yours to get thru until you make the brake swap. Are you going to be swapping to Toyota disc? That might make a difference too. Im pretty sure @cruiseroutfit has rebuild kits and can answer any questions.

We have rebuilds kits:

Brake Master Cylinder Rebuild Kit - Fits 7/1970 - 1/1975 4x/5x Applications - (BMK35010K)

Toyota Land Cruiser Brake Master Cylinder

cruiserteq.com

Or complete new drum/drum or disc/drum or disc/disc brake master cylinder options too!

 

[Grayscale]

Put a kit in it for now. Start Kroil all your fittings now. $50

Nah, not necessary. Do it like I do it, with a pair of wrenches, one for flare-nut, the other is vise grips. Hold both wrenches at once to break anything free. It keeps the 10mm wrench from loosing shape, with torque, and rounding-over the hex on the flare-nut. I forget if it works with impact (hammer) but, I've never stripped my hydraulic lines.

That master cylinder looks rough. I'd really consider checking the bore for rust pitting to see how bad it is. I ran my '73 with pits in the wheel cylinder (after honing), but, I'd worry that the rust will wear out the new seal, as much as it might or might not leak after the rebuild.

If you must swap-out your drum brakes, I'm interested in the spare parts.

 

[rainingagain]

We have rebuilds kits:

Brake Master Cylinder Rebuild Kit - Fits 7/1970 - 1/1975 4x/5x Applications - (BMK35010K)

Toyota Land Cruiser Brake Master Cylinder

cruiserteq.com

Or complete new drum/drum or disc/drum or disc/disc brake master cylinder options too!

Put a kit in it for now. Start Kroil all your fittings now. $50

Yeah - I would just rebuild this one and do the conversion when you are fully ready. Rebuild is trivial as long as you didn't get water intrusion and rust.

Now - I must say, and no offense, but that thing looks like it failed a looooooong time ago. Do a full flush of your system.

 

[Pighead]

I kept my original '74 brake MC through the Toyota front disc conversion, then the Poser rear discs before finally swapping in the 80 series non-ABS MC with a new City Racer booster. I always had good brakes. There are bore size and stroke volume differences between disc and drum that I didn't notice.