Billman250

Wanted to revise my Brake Fluid Gravity Bleed procedure, to prevent ingest if air, and speed process. Gravity bleeding has added benefits over conventional methods, and prevents unwanted mixing of the new and old fluids. Also allows one-man operation. No pumping of the brake pedal will be needed. you won't even need to touch it.

Brake fluid should be changed every 2-3 years for normal drivers, more often for track and autox. Brake fluid that is left untouched will eventually concentrate with enough moisture to cause major rusting of the braking components internally. This can cause hundreds if not thousands of dollar in damage over the years. I have already seen S2000 calipers PACKED with rust and sludge. One was a 2004, 90k miles, original brake fluid.

This job is best performed while the brake fluid is warm/hot. A good spirited drive with lots of braking will warm the fluid and help it drip twice as fast.

The procedure should also be done on a very dry day. No rain or moisture around.

Return from your drive, safely get the car on stands and pull the wheels.

I recommend ATE Super Blue Fluid for all applications. 1 quart bottle of ATE Super Blue is surely enough to do the entire car. You'll use 3/4 -7/8 of the container.

1- Empty the master with a turkey baster. You will get all of the rear of the master empty, and some of the front brake fluid will be trapped. If there is any residue in the bottom of the master, use as piece of paper towel on the end of needle nose pliers to clean out the sludge/dark stuff.

2- If possible, adapt a smaller tiny line to the turkey baster. Use it to sneak in to the front part of the master cylinder res, and empty that last part that you could not reach.

3- Fill the master to the very top with ATE blue. Keep it full as the gravity process runs. Fluid is weight, the fuller you keep it the quicker you will be finished. Leave the cap off for the duration of the process.

4- By trial, I've found the best sequence is RF, LF, LR, RR. Start with the right front bleeder. Attach a 12" clear hose to the bleeder screw (10mm), running DOWN to a container below the level of the brake caliper and let it gravity bleed till it turns blue (no need to sumbmerge the line in brake fluid)
5- . This allows independent scavenging of that LAST BIT of fluid that remained in the front of the master. If you do the LF first, old fluid will move front the front part of the master to the rear, causing unwanted old/new mixing. THIS is why starting with the RF is key

5- gravity bleed the left front wheel until it turns blue. This wheel will go fast.

6- Do the rear wheels, both these can be done at the same time with two clear hoses and two containers. let them drip until they turn deep blue. At this point, let the master cylinder drip down to the full level, and close the last bleeder. Re-cap the master.

You'll have such a great brake pedal from the gravity bleed it will feel like the pedal is welded to the car

I have used this procedure on countless s2ks.

afzan

approximately how long does the actual gravity bleed take (the time from opening RF bleed screw to capping off the MC). Just curious how it compares to using 2 man method/using a bleeder pump/etc

Billman250

If the fluid is warm, it will complete in approx 1 hr 10 min average time start to finish.

Yoohoo

I was always told to have fluid at the bottom of the bleed container and to make sure the tubing is always submerged during the process. Is this detail necessary if you're never touching the brake peddle?

s2000maniac

Chris_Lum

i would like to know too. i assume you don't let it submerge as that will have a neg effect on the scavenging process?

Billman, also another question. for those of us with BBKs, where there are two bleeder valves on a single caliper, does it matter which we do first (inside or outside)?

Sellout

You don't need the tube to be submerged in fluid. It doesn't pull air in because you're not allowing the brake system to come under negative pressure.

dwight

On a technical level, I disagree with #3.

I'm not sure to what level does Billman mean by keeping it full. I top it off after each wheel.

The difference between half-full or full is insignificant. The pressure driving the through the brake lines is a function of the density and the difference in height between the bleeder and the level of the fluid in the reservoir. I estimate that this is about 17", and the difference between constantly keeping the reservoir full is about 1", making it about a 6% difference in pressure. As a result, how full the reservoir has almost no effect on the speed at which fluid will flow.

INDYMAC

Why pull the wheels?

Thanks for your method Billman. Is the bleed order specific to the S2000, or is it a good order for any vehicle?

Sellout

For all intents and purposes, this bleed order will be specific to the S2000. Not all vehicles have the reservoir divided the way it is in the S2000, which is what makes this bleed order more efficient.