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[Millardo]

Because my ‘72 FJ40 only gets dug out of my garage every couple years for a show, it rarely gets driven. I start it on the regular and jack it up and rotate the tires to avoid flat spots.
I pulled it out yesterday, braking several times and noticed brake fluid on the driveway.
I lost about 1 1/2 ounces judging from the reservoir levels…
Fluid was dripping from the spot indicated by the photo, where the brake master cylinder meets the brake boost assist. I wiped it clean, messing up the paint. There seems to be an indentation marked by the arrow which was the source of the drip. I rebuilt that master cylinder 15 years ago but can’t recall much about the assembly. Do those cylinders get pitted with time as it sits with fluid in them? Consequently allowing fluid to get past the plunger?
I wiped it clean and let it sit while I went through the repair manual. A short time later I had my wife come out, started it to activate the vacuum assist and had her pump and stand on the brakes. NO more leak.

I don’t have time to mess with it until after the car show on Saturday… But I am interested in how it might have stopped leaking for now.

Anyone have any insight?

 

[charliemeyer007]

Brake fluid (DOT 3) will pull water out of the air, the contaminated fluid will allow corrosion to start. A little rust bubble could allow fluid out past the seal. Working the seal back and forth a few time might polish off the imperfection and make the leak go away.

 

[Millardo]

Brake fluid (DOT 3) will pull water out of the air, the contaminated fluid will allow corrosion to start. A little rust bubble could allow fluid out past the seal. Working the seal back and forth a few time might polish off the imperfection and make the leak go away.

Thank you for the reply, and that is what I was hoping to hear! Fingers crossed. I didn’t want to dig in to it and find myself waiting on parts, as I only have a few days before the car show.

 

[brian]

I certainly would not drive it till after it was addressed.

 

[charliemeyer007]

Well I would invest an hour and some brake fluid to bleed the entire system.

 

[Mark Jennings]

What I’ve seen in your circumstance, clean dry storage for extended periods, is the seals (cups) have a tendency to shrink allowing a small amount of leakage…..could be water contaminated….but probably a small amount of cup leakage…..

The next time you park it, when you rotate your tires, pump the brakes several times to keep the cups expanded, no need to run the engine, just push a bit harder on the brake pedal.…..I would also pick up a brake fluid moisture probe from Amazon….just to check fluid condition.

One of my vehicles, that sits for extended periods (winter storage) has an oozing caliper, rebuilt it several times….doesn't leak all summer when driven, nor get spongy like air in the system, but parked for several months, I see a little dribble on the rotor. So if I can remember, I get in and give it a few pumps.

I your case to save the paint, a diaper under the dribble would help when up for storage.

 

[Pighead]

I bet @cruiseroutfit has that rebuild kit in stock, might overnight it to you if you ask nicely. It's a half-day rebuild.

 

[cruiseroutfit]

I bet @cruiseroutfit has that rebuild kit in stock, might overnight it to you if you ask nicely. It's a half-day rebuild.

Absolutely and absolutely:

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

Toyota Land Cruiser Brake Master Cylinder

cruiserteq.com

Can ship as soon as tomorrow morning.