So... How do you CCOMPLETELY flush a brake system?

[Deuce Rails]

Gary55 posted an interesting question about DOT-5 brake fluid.

When you look at the boiling points and the lower tendency to absorb water, this stuff seems like it's the stuff for car guys. Especially if you tend to let a car sit.

But it definitely does require a full change of the fluid.

From you guys (like C9) who have actually used the stuff, how far do you have to go in order to do the conversion from DOT 3/4? Would you replace lines? If not, how would you fully flush an existing DOT 3/4 system?

Thanks in advance,

Matt

[SKR8PN]

Flush all the lines with brake cleaner a couple of times and DRY them with compressed air.. I pull and dissasemble all the wheel cylinders,clean them and re-assemble with new parts,including the master cylinder and the proportioning valve. Add new fluid,bleed and drive. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[TagMan]

Yeah, what SKR8PN said!! Just make sure you use NEW rebuild parts. Don't use any NOS or NORS rubber stuff you find at swap meets that may still be in a sealed box that's 50 years old. Rubber deteriorates even in the box. That includes m/c, wheel cylinder & hoses.

[bigron]

i have flushed motocycle brake lines with alchohol and used comp air to dry it. never had a problem.

[BigChief]

I've used DOT-5 in restored show cars and cars with expensive paint only...done it for many customers but I don't like it....here's why. DOT-5 will airate and generate foam under hard repeated use (like in road racing applications). The foam compresses and you loose brake pressure. Its also a real bitch to get all the air and foam out of a system when your bleeding it. Also DOT-5 does not absorb water. Good because it doesn't draw moisture into the system but bad because when moisture enters the brake system - as it always does - the moisture beads on the inner surfaces. The water corrodes these areas badly. The worst part is that when you heat the brakes up the water generates steam pockets....again crating a compressable gas bubbles and you loose brake pressure.

So, regardless of the brake fluid your using you need to flush often (atleast every other year) to avoid brake system problems. Based on the fact that you can get 600+ degree DOT3 and DOT4 fluid and you should flush regularly anyway there is no good reason to use DOT-5....unless you have a show car with very expensive paint and a highly detailed engine compartment/undercarriage that would be damaged by momentary contact with conventional ethylene glycol based fluids.

-Mike.

[bigron]

harley davidson's come with dot 5 from the factory. i'm thinking like for ten years or better

[Chuck Fish]

H-D's been using Dot-5 since the late 70's.