Bleeding Brakes

I replaced both front calipers. While picking up the new calipers and dropping off the cores, I am quite sure the reservoir drained out. I filled it back up and began to bleed the two front calipers. We pumped over 32 oz's of fluid total through the system, but there were still very tiny bubbles visible in the clear vinyl tubing as the system was pumped. There was allot of pedal until the engine was started. The vacuum assist pulled the pedal almost to the floor. The car was drivable, but the pedal just traveled too far. I decided to bleed all four corners, starting with the one farthest away from the master cylinder and working my way back. My son pumped and pumped the pedal as I watched the tiny bubbles pass through the tube. We kept the reservoir full. I did all four corners, but there was always very tiny bubbles visible through the vinyl tubing. We have gone through almost 64 oz's of fluid, but still the pedal still seems to travel too far to the floor. (With the engine running).

My guess is that the master cylinder has air trapped in it since I let it drain out. I noticed two bleeder screws on it. Do I bleed the master cylinder just like the brake lines are bled?

Is there any significants to the fact that without the engine running, the brake can be pumped to a point where the pedal does not travel far? When the engine is started, the pedal travels much farther with the vacuum assist?

Regards

Well not knowing what make/model automobile you are even working on doesnt help much.

You can bleed out the master cylinder.
But how are you bleeding them brakes exactly?

If you are just using a hose in a container of fluid,
thats not the best way to bleed them.

To realy draw the air out you need a vacum pump w/resivoir for best results.
And you should not bleed them with the car on or running.

I thought I had the information included. Must have overwrote it as I was proof reading. Sorry. '92 Grand Am SE. 3800 V6. Front Disc, Rear Drum. Antilock Brakes. Thanks for the feed back. Anymore information will be appreciated. Advance Auto has a Loner Tool Program and they do have a manual device available. Maybe I will try this.

I've done this before, but never had a problem. I am bleeding the brakes by attaching a clear tube to the fitting and watching the fluid flow by as my son pumps the brake pedal. The hose is routed to a bottle of brake fluid and is submersed at the end. The tiny bubbles are always present. Lots of them the size of a pin point. While he is applying pressure, I close the bleeder. I did all four corners starting with the one farthest away from the master cylinder and working my way forward. With the car not running, there is allot of pedal. When I start the car, the pedal travels much farther, but does not bottom out. Way too much pedal.

Sometimes you can help this with new pads.
Since the calipers have to close and move farther. New rotors and such help. If they are a bit warped they push the caliper or slave cylinder apart further and you have to push further again to return to the drum or disc. Also adjusted drum brakes reduces the throw the pistons have to move too.

It will move some as the boost assist moves but you say way too much.

The problem of air is when your just sitting and the pedal seems spungy, goes to the floor, or if you pump till its firm, quit pumping and then start pumping again you have to pump them up again.

You may still have air and may have to re-bleed using your procedure carefully and slow.


Good Luck

New calipers, pads, and rotors on the front. Did not disassemble the rear drums. I bled the master cylinder per an AutoZONE procedure and there were a few bubbles out of the "rearward" bleeder (of the master cylinder), but none out of the "forward" bleeder. There appears to be no bubbles coming out of the Rear Right and Front Left corners. However, I continue to get bubbles from the Rear Left and Front Right corners. Mostly out of the Rear Left. I bled and bled many oz's of fluid through the system. Still bubbles persist. When I stop and check pedal travel, everything feels fine. But, when I start the engine, the pedal travels almost to the floor before stopping. What am I missing?

Please continue to comment. Thanks!

Could be your master cylinder is bad.
Seen any fluid leaking around the booster ?

Your bleeding procedures may not help get the bubbles all out.
Need to close the bleedr valve and then pump them up,
then release the valve(while the pedle is held down) with the hose connected as you were doing , close the bleeder and repeat pumping.
The pressure from pumping should help push the air out it.

hope that helps!

Could be that air is being trapped in the solenoids or accumulator of the ABS system. Use a bi-dir. scan tool to cycle these through to loosen up that air.