bleeding brakes on C3

[Richard M.]

Re: bleeding brakes on C3

To save time when I gravity bleed the rears, I Tee the 2 calipers to a single hose.

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[Jack M.]

Re: bleeding brakes on C3

Not sure if using a Speed Bleeder is still a decent option.
No assistant is needed, as the bleeder has a integrated one way check ball.
(I had created this animation for the originator... that was way back in the mid 90s.)

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[Anthony C.]

Re: bleeding brakes on C3

Prior to bleeding siphon ALL the old fluid out of the reservoir. Then carefully inspect it for sludge at the bottom and thoroughly get the reservoirs squeaky clean with fresh brake fluid and Q-tips. Then fill the reservoirs with resh fluid and start bleeding. Keep the reservoir cap loosely attached as every time you pump the pedal a small geyser of fluid will shoot up from the compensating port, and keep a clean rag handy to wipe up any spills. After you're done and the cover is secured with the bail wires you can use a spray bottle of water and a clean rag to clean up any residue.

I've always preferred the two-person method, one to pump the pedal and the other to operate the bleed valve with command and response. It's fairly quick and a quart of brake fluid starting with an empty reservoir should give a good flush.

Bleed valve operater: say "PRESS DOWN" (and open valve)

Pedal operator: say "DOWN" when the pedal hits the floor

Bleed screw operator. closes valve and says "LET UP"

Pedal operator: let up fairly slow and when at the top say "UP"

Repeat...

Contrary to common "advice" I always bleed the closest corner first. This way the old fluid in the pipe from the m/c to the junction block is expelled via the shortest path.

I've helped a neighbor bleed brakes on his '77, but I forgot which is the front and which is the rear reservoir.

Duke

thank you for your input... I was curious to know why you would drain the master dry .. woundn't that cause more air in system ?

[Ed D.]

Re: bleeding brakes on C3

I think Duke was telling us to clean the debris from the master cylinder before you put fresh fluid in the system.
Ed

[Mark E.]

Re: bleeding brakes on C3

thank you for your input... I was curious to know why you would drain the master dry .. woundn't that cause more air in system ?

No, as long as the reservoir is supplied with fluid while bleeding.

[Mark E.]

Re: bleeding brakes on C3

One issue with doing a pedal bleed on a DOT 3 brake system that has not been serviced in a long time...

Inside the master cylinder, the normal travel of the forward piston finds a smooth cylinder wall. Beyond normal pedal travel, there exists a unused portion of the cylinder. Within that is likely a fair amount of corrosion in the walls, and particles in the fluid if it has not been flushed regularly. This is common if it's a original cast iron master cylinder that has not been sleeved.

Performing a pedal bleed and pushing the piston past it's normal zone of travel could cause the internal seals to be damaged if they come in contact with any corrosion build up inside the cylinder.

On one occasion, after replacing brake hoses on a '70 Corvette, the pedal bleed was going well, until we got to the last caliper. At that time we lost the pedal. We checked all fittings and hoses for leaks, none found. We totally lost master cylinder pressure. We removed the master and replaced it. All was fine.

We later opened up the old master and saw the suspect corrosion in the forward walls of the cylinder, and a damaged piston seal.

Rich

Thanks Richard. I wasn't aware of this risk. Another reason to use the gravity method or a pressure bleeder.

[Duke W.]

Re: bleeding brakes on C3

thank you for your input... I was curious to know why you would drain the master dry .. woundn't that cause more air in system ?

Draining the reservoir will not remove fluid from the actual hydraulic cylinder as long as you steer clear of the compensating port, which is tiny hole just ahead of he front of the piston(s) that feeds fluid to the cylinder.

Once drained you can then carefully inspect the bottom for sludge and clean as necessary.

Then with the reservoir full of fresh fluid on the first pump you are inserting clean rather than dirty fluid.

Duke