These pix are from under my 2003 V8. In crawling underneath I see a couple rubber hoses going from the center, near the gas tank, to each of the rear wheels (bottom pix). I've not noticed these before. They are different from the hydraulic brake lines.

And I notice there is something oozing out of the start of both lines, where they connect near the gas tank (top pix).

I'm having an issue with brake fluid leaking from the master, but I've been unable to locate the leak - what are these lines and do they have anything to do with the brakes?

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Those are the parking brake cables. They run from the parking brake pedal, thru the bottom of the center console and come out where you see in that first picture. So yes, they are part of the brake system but are purely mechanical.

The ooze that you see appears to actually be from your driveshaft, which is flinging extra grease out and it just so happens those 2 parking brake cables exit the body at the same point.

Thanks! I thought it might have something to do with parking brake . . . And an interesting coincidence with the shaft grease!

Any ideas where the brake fluid could be going? I've checked all 4 wheels and see nothing, and don't see anything near the master.

Start following the brake lines, both hard and soft. Remember, there are 6 total soft lines to check - front wheels, behind gas tank to axle and both rear wheels. If any of the hard lines are leaking, you should be able to find a wet spot somewhere underneath.

Had not known to look after the gas tank for flex lines. I've added maybe a quart in the last month. Seems like with that much leaking it should be obvious.

Have you checked the back of the master cylinder under the dash were it comes through the firewall and connects to the brake pedal, you may have to pull back the rubber boot to see if it's leaking out of the back of the unit.

I looked, but I'm not sure how to get to it and don't see a boot to pull back.

I haven't look under there on a 4Runner, but you should find a "rod'", coming from the firewall and connecting to the brake pedal assembly, try and feel the rod as far back toward the firewall as possible and see if you find it wet with brake fluid, it should be dry, if wet then there a leak out the back of the master cylinder, most all master cylinders that I have ever dealt with have a rubber boot, here a link to the master cylinder for 4th Gen 4runners, there a sorta exploded diagram and you can see the rubber boot on the right side of the diagram, you can also see the "rod" in between.

47025-35070 - Master Cylinder - 2004-2008 Toyota 4Runner | Boch Toyota South

Thanks. Not real easy getting into there . . . I did manage to get my fingers into the area a little, and there does appear to be some fluid. I'm taking it in Friday to have it checked, as we have a trailer trip coming and can't afford to keep messing with it - especially not in the mountains!

So I took it to the dealer (the one in Scottsdale is renowned for great, honest service) and they said it was due to the rear shoes being so far down, and that the fluid was going into the rear pistons. They said they found no leaks including at the master cylinder. The pads were down to needing replacement, so I had them do it and turn down the rear rotors (first time).

So I'm wondering about two things:
1. Why would I have to add fluid twice in about a month? I've certainly experienced where pads wearing cause the pistons to use more fluid, but why would it be down twice in several weeks, to the point that the light came on both times?

2. I had the rear pads changed at 198k and now have just under 235k, so why would they need changing again? I was in the mountains when I had them changed last time (198k) - do you think that mountain shop perhaps used really cheap pads?

I had always seen 2-3 times the time between changing rears as I have fronts. But the service writer was telling me the the electronic proportional braking system may actually have the rears engage a couple nano-seconds before the fronts, to keep nose dive at a minimum. And supposedly, because I tow a trailer occasionally, the system might apply more power to the rears. But to have them needing replacement after about 37k doesn't make much sense to me . . .

What do you make of that?