2kturkey

Folks, I am in the middle of bleeding my brakes in order to get trid of the sponginess I have from boiling the fluid.

The problem I have is this:

1. My son pumps the brakes in tha car and holds the pedal down
2. I release the bleed valve and fluid full of air comes out, BUT, just before I retighten the bleed valve lots of air comes out.

I have now gone through almost 500ml (just under a pint) of brake fluid trying to bleed one brake. There is no longer any air in the fluid itself (i.e fluid is clear instead of opaque) but still I get this air coming out the bleed valve from somewhere.

Where is this air coming from? Is it normal?

I suspect I may have a blown master cylinder seal in which case air is being sucked in from somewhere - I just don't know.

Note I have the same problem regardless of whether my son pumps a number of times or just the once, pumps quickly or slowly.

Any ideas anyone??

CoralDoc

Yikes!

I'm not quite sure what you mean by "just before I retighten the bleed valve lots of air comes out". When I bleed (the old fashioned way before Speedbleeders), the procedure is:
1)Have assistant pump and push on the brake pedal
2)Open the bleed valve and let fluid drain into a container
3)Have assistant hold the pedal on the floor (don't let it up) while you close the bleed valve
4)After the valve is closed the pedal can be released and then pressure placed on it again
5)Proceed with 2)

If the pedal is allowed to rise up before the bleed valve is closed, air can be introduced into the system. It takes good coordination between the assistant and the bleeder, so maybe that's the source of the air?

Another source is letting the reservoir level get too low. When that happened to me, it took nearly a pint of fluid to get all of the introduced air out.

If the pedal isn't sinking to the floor when under pressure, I don't think the seals are blown. So, if air is still coming out, and if you're following the correct procedure keep bleeding. Make sure you have plenty of fluid on hand, and keep at it. Let us know how this turns out.

Pepe

Besides what Joshua said above I would strongly suggest that you get the Speedbleeders.

2kturkey

Thanks guys, I think I worked out what it was. My bleed kit I purchased has a rubber elbow which fits on the end of the bleed nipple. The plastic hose is then inserted in the other end of the rubber elbow. This hose to elbow connection is not a tight fit and I think what is happening is that once the pedal is depressed, the flow of fluid down the tube is sucking in the air from the elbow -hose connection. Needless to say, I am taking the kit back to the store and asking for a refund.

The good thin though is that my brakes are bled and the sponginess is gone - phew!!

Bad news is that I checked the pads and one is almost completely gone (no damage to rotor though)- I am going out this morning to buy new pads, but unfortunately here in Australia all I can get is the OEM pads. What I will do is keep my old backing plates and take them to a racing pad specialist who will bond some new linings to my original backing plates.

BTW, anyone know what sort of glue they use to stick the pad to the backing plate with - it must be pretty powerful stuff and I wouldn't mind getting some for other glueing applications. I also assume there is some form of heat used in the bonding process.

Utah S2K

Are leaks in the elbow you describe I have experienced too (on another car). I think your on the right track.....