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When I first got my car, I had to have the brake lines replaced because one broke. Given the following situation, do I need to replace them again or can I just change the fluid and visually check the system for issues?

Brake lines were replaced 16 years ago and DOT 3 fluid was used.

Since that time, I might have 300 miles total on them. Car has sat for at least 10 years, having been moved back and forth from it's resting spot occasionally.

I have a feeling the consensus will be to error on the side of caution and replace them again, but maybe I am underestimating the straight of these lines...my '66 Cadillac still has it's original lines and I have never changed the fluid. It still stops well with no issues (yet).

WHY did the brake line break????? Let me guess. It was rusted thru.

I think your 66 Cadillac, as well as my 56 Executive, 88 Ranger, former 73 Impala and a countless list of other cars we've had answers your question. There is no reason to replace them.

A visual external inspection is good enuf. If thet're not severely rusted then they should be ok.

I did have to replace several over the years. But those showed extreme rust. On one pickup that was only 12 years old.

Visual inspection is the key. One must be reasonable and keep things in perspective.

Thanks PackardV8! I wasn't expecting that. I have been told that brake fluid absorbs moisture and it rusts the lines from the inside out. That is why you are supposed to replace the fluid. I have not seen that in my experience though. That's why I asked the question. I would rather hear from people with experience rather than possible urban legends.

The 43+ year old lines at the time on my Packard were very rusty. I'll look again next time I am under the car, but they seemed in good shape still.

I wouldn't replace them unless they were rusty or leaking. Inspect them carefully especially where they pass through a hole in the frame or where they lay in the frame. Those are favorite places for rust to take hold.

Since you only have a single master cylinder it pays to err on the side of caution, but you will see bad rust years before the line actually blows.

Might be a good idea to flush the brakes. Just bleed the brakes and keep refilling the master cylinder until the fluid comes out clean. Get all the old brown stuff out of there. It's a good idea to do this every 2 years but hardly anybody ever does.

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I disagree. As long as your car has been sitting it's only common sense to replace everything that has to do with your only means of stopping the car effectively.

I've had brake lines that looked perfect but have rusted from the inside out and had them blow on me losing the brakes. Luckily, it was a Hudson and I had the mechanical reserve to get the car stopped.

It's now standard operating procedure to replace everything that has to do with the brake system before I start driving the car anywhere, whether it be down the driveway or around the block.

I concur with turbopackman, steel brake lines can rust from the inside out; especially true if the car has been idle for very long periods of time. Since water is heavier than brake fluid, rust if it occurs normally happens at the lowest point of the system which is usually the wheel cylinders, but it doesn't have to be.

The condition of the fluid should be pretty telling as to the condition of the lines. If the fluid is rusty, thick, or other wise nasty looking, then that would be due to moisture that is attacking both the fluid and in turn the inside of the steel lines.

Dont just go by what it looks like in the master cylinder, flush out all the fluid and look when it is coming out to see if there is any difference in color. If there is any difference it could be a bad area in one spot or more in the system, while the fluid in the master may still look good.

Thanks guys...seems like a split decision here. I like BigKev's idea about looking at the fluid. The very least thing I should do is change the fluid. I know the old fluid will be a little darker than the new stuff...but, if I see any changes in the overall color, that would tell me rust is a problem.

How does moisture (water) get in a sealed system anyway?

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Because brake fluid is hygroscopic and absorbs water from the air, it's a natural occurrence for all brake fluid except DOT 5 Silicone, IIRC.

AND, because the system isn't sealed. There is a vent hole in the filler cap to allow air to enter and leave as the fluid level rises and falls in the hydraulic chamber. That's how the air (and moisture) gets in there in the first place.