Bleeding the Brake System

Project At A Glance
Time 0:30 Recommended Interval 2 years or 30,000 miles
Total Time 1:20 Standard Tools turkey baster, 10mm combination wrench
Difficulty 3 of 5 Special Tools n/a
First-Time Cost $60 / $300 Parts  brake fluid (1/2-1 liter), speed bleeders (optional)
Subsequent Cost $0 Service Manual Pages 19-10,11
People Required 2 (or 1 w/ special tools) Prerequisites jack car, remove wheels
Notes: If you track the car, you should bleed the brakes before and/or after each event.

Why Bleed?

 The NSX, like all modern cars use a hydraulic system to operate the brakes. For  a hydraulic system to function it must be closed and completely filled with  fluid, and leak-free--no fluid out or air in. In a closed, properly sealed  hydraulic system, the following law is true: fluid cannot be compressed to a  lesser volume, no matter how high the pressure. We call this hydraulic fluid  "Brake Fluid". Unfortunately, no brake system is completely closed and  eventually air, which contains water vapor, mixes in with the brake fluid. This  is bad news because it lowers the boiling point of the fluid. Boiled fluid  leaves behind tiny gas bubbles which are compressible and gives us that initial  "mushy" pedal feel. In bad cases, this "air" in the lines  can severely limit the amount of hydraulic force available to stop the car! It  is wise then, to replace this contaminated fluid; the service manual recommends  every 30,000 miles or 2 years. A good DIYer will bleed the system at least  annually. Tracking the car demands perpetual replacement of the fluid. A street  driver will want to pay close attention to the Wet Boiling Point properties of  the fluid, a tracker will only be concerned with the Dry Boiling Point  properties as they will be changing the fluid before it has time to absorb  water.

Use a DOT 3 or DOT 4 fluid only, DOT 4 is preferred. DOT 5 is silicone-based and is incompatible with our brake system. Try not to mix brands of fluids.
Brake fluid is an excellent paint remover. Immediately flush with water if you accidentally get some on your car.
Wear gloves and safety glasses to avoid an improper relationship with the fluid.

Dan’s Recommendations
I Use Motul 600, ATE Super Blue (Let’s support our NSX vendors!) or a similar high-temp fluid, speed bleeders and the Griot’s Garage bleeding bottle. I track my car so using a good high-temp fluid is mandatory. Griot’s bottle is only $35 and is worth the price. Speed bleeders make the job a quick one-person operation and are reliable and inexpensive. Even if you don’t’ track your car, you should still use brake fluid that meets DOT 4 specifications for wet boiling point (311 F).

CAUTION: [BZ] Keep the brake fluid away from powdered pool chlorine. When mixed, it will spontaneously combust after about 30 seconds.

[AWN, BSD, HS] The reason for bleeding fluid out of the brake system is that brake fluid can absorb moisture even when it is in the system. As this happens, the fluid becomes less resistant to boiling. Bleed your brakes at least once a year, or before (and maybe during and after) a track session. Only use brake fluid that hasn’t been previously opened.

Jack up car. Remove wheels. Start at the corner furthest from the master cylinder (right-rear for most of us). Remove plastic or rubber cap over bleeder valve in caliper. Use box end wrench to loosen bleeder valve.

Instead of using a “catch pan”, use a bit of surgical or aquarium tubing that fits the bleed nipple tightly, make a vertical loop with the tube so fluid stays up in it – or keep the end submerged in the old fluid. If you do this, you’ll drastically reduce the chance of air getting sucked back in. I use a 1-pint plastic OJ bottle with a bit of wire around the its neck — the wire will let you hang the bottle on a nearby bit of hardware.

Make sure that the end of the hose is always immersed in the fluid in the bottle. Immersing the end of the hose in brake fluid will keep air from being sucked back into the system. If you use the bottle, you don’t need to close the valve after each pump, you can just let your wife pump the pedal until you get a steady flow of bubble-free fluid into the bottle. When you see that steady flow, have her hold the pedal at the bottom of its travel, then close the bleeder valve, let her release the pedal, and move to the left rear, then right front, then left-front wheels (in that order).

By the way, Carroll Smith and Mac Tilton say that the brake-pedal pumping must be done GENTLY so as to prevent the fuid from cavitating in the system, so ask your wife to press the pedal BY HAND. On the RR caliper do about 8-10 pumps, the others only need 3-4.

Do NOT get brake fluid on paint. NEVER bleed the brakes with the brake pads removed.

Bleeding the brakes never means “emptying” them.

There are really two different things to do with brake fluid: bleed and flush. Bleed is where you replace a little of the fluid. This may be done after a brake pad change or after boiling the fluid in the calipers.

Flushing the system is where you replace all the fluid in the system. This would be done on a yearly or bi-yearly basis or after major brake system work.

The procedure for both of these is to remove fluid from the brake caliper bleeder valve and:
1) open bleeder valve
2) press brake pedal and hold down
3) close bleeder valve
4) release brake pedal
5) repeat

(Have an assistant do the brake pedal pumping.)

You keep the brake fluid reservoir from going below the “min” line during this procedure by adding brake fluid after 8 pumps or so.

Both bleeding and flushing the system are often referred to as “bleeding” because the valve on the caliper is called a bleed valve.

Only when doing a caliper rebuild would you worry about “lubricating” anything with brake fluid. When replacing the piston(s) in a caliper, most systems instruct you to lubricate the caliper bore with brake fluid before inserting the caliper. Do not put in any other lubricant unless the instructions specifically require it. I am fairly sure the NSX instructs you to use brake fluid as the lubricant. The pistons sit in brake fluid their entire lives anyway.

[GL]  One thing to be careful of when bleeding/flushing brake fluid is to not push the brake pedal further than what you
normally do during braking.

Pressing the pedal farther than normal could cause a leak in the master cylinder. To prevent this, try putting a piece
of wood block under the brake pedal to limit the travel.

You can also bleed the system using a handheld vacume pump. After flushing with the manual pump, I’ve found that it
requires a final manual bleed to remove small air pockets.

Other than that, it is pretty straight forward, refer to the service manual for bleeding sequence.

[HPA] 1. Brake fluid is an excellent paint remover;  2. NEVER shake a container of brake fluid irregardless of type. The
fluid won’t compress but the tiny air bubbles will.

[BSD] When you get back in the car, you will have to pump the brake pedal a few times to get the fluid back out to the caliper.

[DO] Brian points out a VERY important step. I forgot this step ONCE, backed out of my garage and almost (within 6″) into my house. Needless to say, I ALWAYS make sure I have a firm pedal after I do any kind of work on my breaks.

[MBA – 99/8/21] The way I do it is to remove, either by bleeding or by sucking out (you should buy a 3 dollar turkey baster) all the fluid in the reservoir until you can see the intake opening at the bottom of the reservoir. I leave just enough fluid to cover the holes. Then slowly, as not to mix the fluids more than necessary, I fill the reservoir with new fluid to the very top and then drain, only by bleeding, about half this new volume out, then top up. IMO, only the most minuscule amount of the old stuff might be left behind.


[CA] I just called and ordered a set of 4 speedbleeders! Check out their web site at

These are pretty cool and are getting rave reviews from all the magazines from motorsports to cycle world. They eliminate time consuming and messy brake bleeding, simply install, and loosen 1/2 turn, slowly step on the brakes about 4-5 times, tighten and your done, this bleeds the brakes without allowing air back into the system using a spring check valve! simple, ingenious! COST and TIME EFFECTIVE!

Call 630-739-4620 ask for Mike and tell him you are an NSXCA member and recieve 10% discount. Cost should be 6.50 each x (26.00 ) – 10% = $23.40 +$2.00 SH

TOTAL of 25.40!

The right size for the NSX is 10mm x 1.25 or part number SB10125.

[GL] Regarding the bleeders, I’ve experienced very minor leaks around the threads of the bleed fittings after bleeding the clutch and the cooling system. This also happens on the brakes of my Honda motorcycle. Not sure why Honda’s do this. What I’ve found to work is to loosen the fitting and let some fluid out and retighten it. If this doesn’t work, remove the fitting and wrap a small layer of teflon tape around the threads. Make sure you route the tape in the right direction so the tape does not strip off when you tighten the fitting down.

[AC] I wanted to give my endorsement to Speed Bleeders. I was originally sent the wrong size but a Saturday call to Mike Sulwer (630-739-4620), he not only got the correct ones in the mail asap, but also established the size of the clutch bleeder as well.

At Mike’s suggestion, I tried one of the undersized brake bleeders in the clutch and bingo! Here’s the part numbers:

Brakes require SB10125 while the clutch takes SB8125

Total cost for the 5 bleeders was $34.50 including shipping and a 10% discount to list members. They work as well as advertised and IMHO better than all the other options I’ve tried over many years and various cars.

[DO] I installed my speed bleeders yesterday. I bled the brakes and clutch according to the service manual, and all seemed to go well…until I got in the car (still on stands fortunately) and tested for a hard brake pedal. The pedal was pretty hard, but then it slowly sank to the floor, I tried it a few more times and it did the same thing. When I got out of the car I had four nice puddles of brake fluid on my nice clean garage floor. PISS! So I went around the car and torqued the bleeder screws (which were already pretty tight) a little more. But they still leaked a little fluid. So I tightened the hell out of the valves and they finally stopped leaking.

I know these are tightened *way* beyond spec torque. The clutch valve seems to be working just fine with the spec torque. I have installed “Speed Bleeders” made by Russell on other cars without this problem.

[SS – 99/3/3] If these things aren’t the cat’s meow, I don’t know what is. I have wondered for years why brake bleed screws don’t have check valves inside to make bleeding fast and simple. Speedbleeders are exactly that. These replace your existing bleed screws, and once you get them seated, open them up 1/4 – 1/2 turn, push the pedal a few times, and you are done. A one person, very fast job. Part number for the NSX is SB10125, cost $7 each from

The only bad thing about them is that they do not come in metric nut sizes. The threads are metric, but the nut is 3/8″. This is also the only bad thing I can say about the SS/Kevlar hoses, as the nut to attach the hose to the line is 11/16″