The Stovebolt Site Forums The Shop Area Engine Shop Should I flush the brake lines? Or leave them alone?

I was going to flush out the lines on our '62, because the brake fluid looks like it might be 40 years old. But after the warnings I got about running Mobil 1 in a 235 engine and the leaks I might cause, I'm wondering if I should do it.

If I put fresh brake fluid in all the lines am I going to start having leaks? Like in the wheel cylinders?

Thanks in advance.

Sorry for the extra post....

Brain is apparently still not fully engaged with fingers!

Flushing the brake system with new fluid is a good idea.Make nsure to use only D.O.T.3 or 4(5 is a silicone based fluid and not compatible with the other fluids)
MAKE SURE you do not get the fluid level too low in the master cylinder or it will get air in the system.Just keep addind fluid or checking the level after letting fluid out through the bleeder valves at the wheels.
when you think you are finished, do not completely fill the master cylinder as the level needs to only be 1/4 in from the top or the fluid will not have the room to come back from the wheel cylinders after you step on the pedal to stop and your brakes will not release

Thanks Mechainiac.

Any risk of making the wheel cylinders leak from the new fluid?

There's always a risk of making the cylinders leak. Cause of the leak is usually from corrosion due to dirty brake fluid. If they do leak, they needed replaced anyhow.

Brake manufacturers are now recommending flushing the system every year. Personally, I think that's overkill, but I won't tell someone not to do it.

The best thing to use to flush out the brake lines is rubbing alcohol. Squirt it in the lines, let it sit a few minutes and blow out the lines with air. Repeat and let air dry and reassemble.

'52s method works best on a brake system that is totally dissasembled for major service.

In your case, just connect a clear hose to the bleeder screws. Put hose in mason jar to catch old fluid. Pump and add fluid to M/C until clear fluid comes out at each wheel.

Moisture in lines and lack of use will kill a brake system the quickest. I had rebuilt the rear brakes on my '54, and then it sat up. When I got her going again, the new wheel cyls were ruined from sitting.

good luck

chip

I have to disagree on the rubbing alcohol unless the system is disassembled and you can be sure everything is dry. Problem is the water content of most rubbing alcohol is 30%, and brake fluid absorbs water. That's why denatured alcohol is recommended. While not completely water-free, I'm thinking its water content is less than 2%. I agree with the brake fluid flush. And don't save a can of fluid with just a smidgen in the bottom. It will absorb water. I buy a new quart of DOT3 for a flush, and save the leftovers for paint stripper on model trains.

Wouldn't it be better to go ahead and take the system apart, flush it and fill with DOT 5? Silicone won't absorb water, will it? I think most military and goverment vehicles that may only see occasional use, or long storage periods, spec DOT 5. I've been using it in a couple of my old cars for 5 years+ without problems, and the brakes are about the only thing that will work after I leave a car set for over a year. (I'm not smart enough to start them occassionally)

No, don't use dot5 with a system that has not been rebuilt with new seals and hoses. Dot3&4 make rubber swell to keep the seal, and 5 doesn't, so the old seals will start leaking. Dot4 done annually is great.

howziit guy!

JMO, flush with approved fluid, and replace components, as needed.