Replacing Brake fluid

[Toms007]

Gentlemen, I am going to be in Tennessee the first week of August. I have decided to drive the Vette so I can do the "Tail of the Dragon". With this planned, I am figuring that I should probably change out the brake fluid in my car. I want to completely flush the system and put in DOT 4 fluid. My question is; How do I completely flush the system out? I can pretty much suck out all the stuff in the master cylinder and the lines and calipers, but what about the ABS?

Any one have some suggestions/tips/helpful advice on how to accomplish this?

Oh the reason for wanting to do the DOT 4 stuff is that I am planning on tring some autoxing and have been advised (by several competent sources) to do this first. And I figure that the "Dragon" will probably test the system as well.

 

[fatboyreyn]

fluid change

I had an 82 before my 86, and had a hell of a time bleeding fluid after full brake job. Tried power bleeding, vaccum bleeding, and still had to do it the old fashioned way with somebody pumping the brakes. I would suggest power bleeding the system, ( connect a jug of fluid to brake resivoir, pressureize jug, then bleed all four brake lines untill jug is almost empty. There should be a bleeder at the ABS station too. Good luck.

 

[c4cruiser]

One easy way to flush and refill the system is to purchase a set of "Speed Bleeders". These bleeder screws replace the existing bleed screws on your calipers. Find the ones for your car here: http://www.speedbleeder.com/

Speed Bleeders have a small check ball and a spring inside. Once installed, you simply loosen the bleeder about 1/4 to 1/2 turn and begin pressing the brake pedal. The spring behind the ball allows the ball to close the hole in the bleeder when brake pressure is released; no air gets in.

Once you have the Speed Bleeders installed, use a common turkey baster to suck as much fluid out of the master cylinder reservoir as possible (don't allow fluid to uncover the ports to the master cylinder piston) and refill with fresh fluid.

Connect a length of plastic tube to the bleed valve and put the other end in a jar. This simply allows the old fluid to be collected neatly. Begin pressing the brake pedal (have the motor running as engine vacuum helps with pedal pressure). When you see clear new fluid coming out, simply close the bleeder and go to the next bleeder using the proper bleed sequence.

It will take about a quart of fluid to do a complete exchange of fluid. As far as the ABS unit, the only way to flush it is to have a GM Tech II Scan Tool. This scan tool along with the brake system module, will provide power to the ABS pump and fluid will pass thru it.

But every time you start the engine and the car moves foward thru 3-4 MPH, the ABS does a self-test (the buzzing you hear behind your head!). This test will move a small amount of fluid through the ABS system and lines so it is self-bleeding in a way.

Unless you have some high performance or close to race-level brake pads, good DOT3 fluids should work for autocross. A-X events don't typically have speeds high enough or braking efforts like say a track day that really warrants DOT4.

Look for the wet boiling point of brake fluids. That is the true indicator of a fluid's ability to handle heat.

A good DOT3 fluid is the Ford MotorSports Heavy Duty fluid. Castrol LMA is another good DOT3 fluid and both have wet boiling points at the top of the DOT3 range. Valvoline is another good fluid.

For a good DOT4 fluid at a reasonable price, get some ATE Super Blue. This fluid has a wet boiliing point of 392 degrees and runs about $12 per liter. This fluid is blue in color so you can easily tell when your flush is complete for each brake line. ATE also has Typ 200 fluid which is the same as theSuper Blue except it's a golden color. Swapping these two between flushes allows you to tell when one fluid is out of the system by seeing the color change.

 

[milehigreg]

Braking

I agree with C4Cruiser as far as the need for DOT 4. My experience with autocross ( one day ) is that you use your brakes minimally. In fact , the pro who walked us around the track made the statement that we should use our brakes as little as possible. The brakes slow down the car much faster than the engine speeds it up. It about a good line and being smooth. On the other hand, at the track ( again one day ) braking was at a premium. I went to the closing weekend of 2nd Creek raceway here in town and did several 20 minute sessions. HARD braking required at the end of straights. I did not change my brake fluid prior, it was a last minute deal. As soon as I pulled off the track after each session the brake fluid would boil.

 

[Toms007]

Well, I'm off to find the highest "wet boiling point" DOT 3 fluid I can find to replace the old stuff with. I'm going to trust you guys on this one.