Bleeding Brakes - A Beginners Question

[Mike Bonkalski]

I know how to bleed the brakes to evacuate air in the lines.

Start at the caliper farthest from the M/C, have partner pump brakes, hold pedal to floor, open valve, let air bubble escape, close valve, move to next caliper. All while keeping the fluid level in the M/C acceptable.

My question deals with a complete fluid change over. Do I just go to the farthest caliper and start pumping until I see a fluid color change (going from gold to blue), then repeat with the other calipers?

I just want to make sure I am doing this right.

[RANDY P]

Yep. However be careful if the MC is old. Pushing on the cylinder past it's travel may cause internal leakage in the MC.

Check out the Motive Power Bleeder sold on this site. Easiest way to avoid issues.

rjp

[masraum]

Yes, that's exactly how you do it.

There is the general consensus here that using the method above can damage the piston seals in your m/c. Under normal conditions the piston only moves so far into the bore, so anything past that can collect gunk and become rough, by pumping the pedal all of the way to the floor you can damage that seal which will then require a rebuild or replacement. There are several other methods that are prefered, vacuum, like the mightyvac, pressure, like the motive, and even gravity bleed.

[Mike Bonkalski]

Thanks for the info. I had the brakes lines disconnected for rear monoball installation and proceeded to bleed the brakes with the pedal pumping method. Now my M/C is not happy and needs a rebuild. Nothing like the feeling of the pedal going to the floor when you are approaching a RR crossing with the gates going down. YIKES!! I quess it is time to buy a Motive.

[Jim Sims]

From an old post; probably too much detail:

Here's what I do (for cars with each caliper having a single bleeder valve):

Gather tools and materials: floor jack (with wood piece on lift pad), jack stands(4), soft socket for wheel nuts, 100 ft-lb torque wrench, 1 liter Ate brake fluid (in a different color than currently in car), Motive pressure bleeder, small 7 mm and 8 (or 9?) mm box end wrenches, 8-10 " length of clear hose to fit over bleeder valve nipples, rubber cap or bit of rubber or plastic hose with one end plugged (golf tee, etc.), container to receive old brake fluid (small glass jar), metal can for old brake fluid disposal, cardboard box lined with plastic trash bag sufficient to hold motive bleeder, small stand or box to set glass jar on, old newspapers, paper towels and hand wipes. One may also consider having a spare bleeder valve available (some car use two sizes - front and rear can be different) and new rubber bleeder valve dust caps.

Place car with adequate space to work around vehicle (no tight garages). Loosen wheel nuts. Jack car up, place on jack stands and remove wheels. Put newspapers under each wheel position. Remove bleeder valve rubber dust covers and clean if reusing. Clean dirt off bleeder valves as required. Open front hood.

Brake fluid will be handled after this point; DONT GET IT ON YOUR PAINT! It will damage the paint and attempting to wipe it off will make the damage worse. Some attempt to blot or wash it off but the damage will still occur. Take your time. Wipe up spills (on floor, non-painted car chassis surfaces and tools) immediately and thoroughly. Watch your hands, clothes and shoes. Clean your hands often and don't touch or lean on the car (the reason for not having a tight garage).

Remove MC reservoir cap (debris screen under cap may be left in place) and vent hose (take care that you don't snap off the integrally molded hose barb) and install vent cap or bit of hose with golf tee or other plug. Place new fluid in Motive pressure bleeder (PB) tank, place bleeder in plastic trash bag lined box and place in front trunk area next to MC reservoir and attach Motive PB cap to MC reservoir. Pump up PB (follow instructions on PB) to around 10 psi (higher pressures may run the risk of blowing out the rubber bushings which seal the plastic lines from the MC reservoir to the MC. If you can't hold pressure check for a leak (MC reservoir cap, vent line hose barb plug, PB tank lid). Look for leak from MC area; if the plastic line to MC joint rubber bushings are bad there can be a leak from MC.

Starting at the wheel position furtherest from MC (RR in LH drive cars) place wrench over bleeder valve hex and attach clear hose to bleeder valve nipple. Place hose in jar (I sit the jar on a box or stand of some kind so it is at a convenient height). Open bleeder valve (take care to pull the wrench in the correct direction; the bleeder valves are on the inside of the calipers so one can get mixed up). If bleeder valve won't open and shows rust or corrosion spray the base of it where is screws into the caliper with "Kroil" or other penetrating oil (not WD-40) and wait 15 minutes and try again. The hose will want to twist as the bleeder valve is opened so take care that it stays in the jar and doesn't tip the jar over. Allow the brake fluid to flow until one obtains a full transition to the new brake fluid color. Close the bleeder valve; don't over tighten - I use small combination wrenches to limit my ability to over torque. Remove hose and wipe up any spilled fluid. Look for leaks from bleeder valve; if leaking tighten a bit more. If no leaks, install cleaned or new dust cap onto bleeder valve. Repeat at other wheel postions working towards MC (LR, RF and finally LF). I empty the jar of old brake fluid after each wheel position. If you put the full liter of brake fluid in the pressure bleeder you should have plenty of fluid to bleed the entire system but check that you always have enough fluid in the PB tank to keep its intake well covered (one can tilt and shim up the cardboard box to force the fluid to the intake side of the tank). Also check PB pressure; my experience is that I don't have to repump it much if at all. I usually make a second pass around the wheel positions to ensure I have exchanged as much fluid as possible in the wheel calipers.

When finished with all wheel positions depressurize the Motive PB by unscrewing ITS lid (follow instructions). DON'T UNSCREW THE MC LID FITTING FROM THE MC UNDER PRESSURE! Check brake pedal for firmness (CLEAN HANDS, CLOTHES AND SHOES! Wife or girlfriend in clean attire is useful for this task if they know what the brake pedal should feel like). Check all wheel positions for leaks. If needed add fluid to MC reservoir, replace MC reservoir cap (check cap for cracks and gasket if equipped with one). Remove vent cap or plugged hose piece and reinstall vent line. Remove Motive PB from trunk and remove surplus brake fluid from Motive PB and wipe it out with clean paper towels. Secure old brake fluid and surplus new brake fluid. Pick up newspapers under wheels. WASH HANDS!

Close front hood. Remount wheels, install lug nuts by hand and seat them well by hand using soft socket and using the cross-wheel tightening pattern. Lower car and torque wheel lug nuts to 50 ft-lbs using cross-wheel tightening pattern, repeat but torque to to 94 ft-lbs.

Test drive, starting out carefully as if you have no brakes. Test brakes with a gentle stop in driveway. After test drive look for leaks. Good Luck! Jim

[Mike Bonkalski]

Jim,

Wow! I didn't find this post during my original search.

Thanks.

[Neilk]

If you disconnected your brake lines or are changing master cylinders, buy some cheap brake fluid to do your initial flush. Once you get a good pedal feel, rebleed your brakes with the good stuff. It can take several liters of fluid to bleed a new system. No point in wasting $12/ltr fluid just to bleed your brakes.

[84toy]

Before you start bleeding, suck out all the old fluid out of the M/C and replace with new. This way you will know as soon as the new fluid arrives at the caliper and it speeds up the process and you won't keep mixing with the old fluid

[911pcars]

If you're just beginning, you don't need to purchase all the paraphanalia. Just get a couple of box wrenches for the bleeder screws and a length of PVC hose from the hardware store that fits snugly over the bleeder screw. With the hose attached, open one bleeder and watch the fluid drain through the hose into a waste container.

Watch the master cylinder reservoir level as it almost bottoms out, then add fresh fluid. When you see new fluid in the tube, close the bleeder and repeat at each caliper.

If there are air bubbles in the system, you'll see them exit through the hose.

Next time, if you want to do this faster, buy the pressure bleeder. However, some manage to use more than 1 liter with a pressure bleeder. Minimum waste with gravity.

Sherwood

[rickeolis]

What do you guys think of the little bleeder style valves that don't allow air to suck back in?

I ask because I just ordered a set...

[aigel]

Rick:

The speed bleeders are great, but you will still potentially wreck your M/C by pedal pumping.

George

[JeremyD]

I am a big proponent of the speedbleeders - just use short choppy strokes of the brake pedal. as others have said - long strokes tend to rip the MC seals...

[rickeolis]

Got it, thanks guys-

[Grady Clay]

I like to use gravity for initial movement of fluid.
A little grease on the bleeder valve threads prevents air from entering there. It also allows you to open the valve next year.

Many have air in the system and get no pedal pressure. Here is a solution:

With the reservoir full, flick the pedal down an inch or so several times. This helps open the inlet valve.

Open a bleeder valve at a caliper while the pedal is still “up.”

Depress the pedal no farther than normal (I agree about MC damage.)

Re-seal the bleeder.

Let the pedal back up.

Repeat.


If a master cylinder leaks, the first symptom is brake fluid in the rubber bellows. Stick your proctological finger behind the brake pedal and massage the bellows. Any sign of brake fluid is a concern. The next is finding consistently lower level in the reservoir. You never want to get to the final symptom – NO BRAKES!


Best,
Grady

[MY83SC]

GREAT post Jim!