As I wrote about back in April, when I went out to my rented warehouse space in Monson for my long-delayed post-winter visit, I found that all my cars needed something. The most trivial was the Bavaria’s dead battery, discharged to nine volts even having been left disconnected. The worst was the Lotus actively leaking fuel. Somewhere between was Louie the ’72 2002tii (the Ran When Parked car) whose brake fluid reservoir was virtually empty. Because the brake reservoir is also used by the clutch hydraulics, and because the line feeding the clutch master cylinder is a tap off the side of the reservoir, if the fluid level is even with the clutch port, it means that the leak is in the clutch hydraulics, but if the reservoir is empty, it’s a brake leak. There was no question this was the latter.

The funny (yeah, ha ha ha) thing was that this had happened before. Last summer was a blur due to family health issues, resulting in the cars in Monson barely getting used, so I believe I first saw this when I went out there two springs ago. At the time, I searched underneath the car and didn’t see any puddles of brake fluid, looked on the insides of all four wheels and tires and didn’t see anything running down the sides, and looked at the hoses under the reservoir feeding the master cylinder and didn’t see them obviously leaking, so I refilled the reservoir, mashed the brake pedal a bunch of times, assured myself I wasn’t about to lose the ability to stop the car, drove it home while stopping repeatedly at rest areas to check fluid level (which remained fine), and tried to find the cause.

Puddle-less brake fluid loss usually means the fluid is either going into the power booster (or, in the case of clutch leakage, the pedal bucket), but I checked the first by snaking a zip tie down into the booster and it came up dry, and there was no fluid in the pedal bucket. After a bit of head-scratching, I pulled off the rear wheels and found a tiny amount of dampness at one wheel cylinder. I ordered cylinders for both sides, but when I used the car that summer, there were no dramatic changes in brake fluid level, so I never installed them.

This really did appear to be an almost insignificant amount of wetness.

Fast-forward to now. I was looking at exactly the same set of symptoms, so I did exactly the same things. Again I looked for fluid dripping under the car or running down the wheels and tires, and found none. Again I pulled off the brake booster hose and slid a long zip-tie down into the booster, and again it came up dry. I also gave a look at the cloth-braided rubber hoses connecting the reservoir to the master, and nothing looked obviously wet. I was about to jack up the car so I could pull off the rear wheels and see if the rear wheel cylinders had unleased a gusher when I got stopped by the train-wreck of cars in my tight garage taking up both the mid-rise lift and the level floor (yeah, I know, happy problem). So I instead took my plastic ramps, stuck them and Louie in front of my house, drove it up on them, and had a look underneath to see what I could see.

The ramps really do come in handy for these just-need-to-get-under-the-nose sessions.

Bingo. There was brake fluid running down the left frame rail.

To channel George Takei, oh my!

The fact that brake fluid is highly corrosive and eats paint was dramatically depicted by the Agave green strip hanging from the side of the frame rail. On the one hand, the photo below isn’t quite what it appears, as it’s not completely-eaten-off paint but a rust-inhibiting coating with a thin layer of paint on it, but still, yikes, right?

Yikes! Oh, I said that.

So where was the brake fluid coming from? I gave a more careful look at the cloth-braided rubber hoses fed by the reservoir, and now could see that the forward hose was darker than the rear one, indicating that brake fluid was permeating through it. There was also was some wetness on the front section of the master cylinder itself.

Gotcha. Maybe.


And looking underneath the master cylinder, I saw that one of the metal brake lines was wet, as was the top of the frame rail.

Gotcha. Definitely.

Clearly the forward braided cloth brake hose was leaking and needed to be replaced. These hoses are a push-fit onto barbed fittings under the reservoir as well as the fittings emerging from the rubber seals at the top of the master cylinder. When I tugged the bottom end of the hose, it was still held fast to the barb, but I found that I could easily rotate the hose around the fitting with absolutely no resistance, so apparently it was leaking both from the lower fitting as well as through the hose itself. I had a vague recollection of having replaced the other hose (the one that wasn’t leaking) when I resurrected the car in Jake Metz’s pole barn in Louisville seven years ago. Although it was still okay, I replaced both hoses. I refilled the reservoir, verified that things appeared tight, then unloaded the better part of a bottle of brake cleaner both onto the frame rail as well as inside it before rinsing the area thoroughly with water.

When I have the chance to get the car up on the mid-rise lift, I’ll likely shoot either some oil-based rust inhibitor or Waxoyl into the frame rail to ameliorate whatever corrosion the brake fluid has wrought. And I’ll pull the rear wheels off to assess the condition of the rear wheel cylinders.

I’m relieved to have finally found and fixed this problem. Of course, given the historically long cycle time for the reservoir to drain itself, I guess I’ll really only know for certain after I’ve let the car sit over the winter.

Rob Siegel


Rob’s newest book, The Best of The Hack Mechanic, is available here on Amazon, as are his seven other books. Signed copies can be ordered directly from Rob here.




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