leaking hydraulic brake booster

[MadCityRich]

So I noticed a little puddle under the 4Runner today. Checked underneath and it appears that there's brake fluid leaking from somewhere in the hydraulic booster area. I'm wondering if there's a typical failure point or good way to confirm the issue.

This is for a 2002 model with about 188,000 miles on it. Last summer I went from the 199mm tundra brakes to the 231mm tundra brakes. I anticipated some potential for developing an internal master cylinder leak, but this is clearly an external leak. The brakes feel good.

The reservoir is just a bit over max. The fluid is fresh from this summer. It's not leaking out of the top of the reservoir, but it is technically a little over full. I don't know if that could cause a pressure related leak under the reservoir or not.

The 4Runner is no longer my daily driver. It's been too cold to do much in the way of diagnostics, but I was going to get the booster to cycle and see if I could find the source of the leak.

Any guidance or experience would be helpful.

Thanks much,
MadCityRich

 

[nissanh]

If you see brake fluid right under the master cylinder/brake booster, try simply loosing and turning the 12 mm nuts 2 or 3 rounds so as to give some gap between the master cylinder and the booster. At this moment, if you notice oil coming out, the brake washers in the master cylinder has gone bad.

Having fluid above the max mark should not spill oil, have slightly above max and no spills.

 

[MadCityRich]

I'm digging into this, but am not quite clear on which nuts you are referring to. There are a number of brake lines that connect to the MC and red one that seems to go between the MC and booster. Is it one of those or something else?

I'm seeing a couple of possible fluid sources right now. One is from the rubber end of the MC that you can see in the engine bay, another is from the banjo bolt that connects one of the brake lines. Or perhaps something else I can't see. And the fluid could be getting spread around a bit from wind in the engine bay.

Thanks,
MadCityRich

 

[nissanh]

Can you please post a picture where the MC it mounted to the booster?