bleeding brakes on C3

[Anthony C.]

HI,I am flushing out my old brake fluid ;just wanted your opinion on gravity bleeding verses the old school pumping method thanks

[Ed S.]

Re: bleeding brakes on C3

Gravity works - it is slow, pumping is faster - either way, be sure you do not get down to "air" in the MC reservoir. Also - it is messy but - before you start, take a screwdriver or a small brush and carefully agitate the fluid in the reservoir - you will be amazed how much sediment is sitting on the bottom that will float in suspension in the old dirty fluid. If possible, suck it out with a baster (don't tell your wife)..... - better than pushing it through the lines and calipers. Best to start with a fluid in the reservoir. Good luck.

[Tom R.]

Re: bleeding brakes on C3

Like others, I've played with various methods over the years for bleeding the brakes, whether its pumping or gravity. However, my most recent find is the motive bleeder. Check it out!

https://www.motiveproducts.com/pages/power-bleeder-instructions

[Duke W.]

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

[Tom R.]

Re: bleeding brakes on C3

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

Form follows function...or in doubt, follow the brake lines from the M/C...one grovels forward while the other meanders toward the rear.

[Patrick H.]

Re: bleeding brakes on C3

Nothing like using the Motive bleeder with the upgraded metal cover and a larger C-clamp.
Much better than the 2 person method or gravity.

[Ed D.]

Re: bleeding brakes on C3

Just purchased a Motive bleeder and plan to use it after I install newly rebuild trailing arms and calipers. I got tired of asking my wife to get in the car on the lift and pump the brakes of command. I hope can get the Motive to work as well as others have reported.
Ed

[Mark E.]

Re: bleeding brakes on C3

If possible, suck it out with a baster (don't tell your wife)....

Don't tell her? Should I secretly return the baster to the kitchen?

[Ed S.]

Re: bleeding brakes on C3

Don't tell her? Should I secretly return the baster to the kitchen?

Not advised. Go to a department store and buy her a new one for Christmas.

[Richard M.]

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

[Patrick H.]

Re: bleeding brakes on C3

Just purchased a Motive bleeder and plan to use it after I install newly rebuild trailing arms and calipers. I got tired of asking my wife to get in the car on the lift and pump the brakes of command. I hope can get the Motive to work as well as others have reported.
Ed

Ed,

Let me know if you need tips on how to use it.

PH

[Ed D.]

Re: bleeding brakes on C3

Ed,

Let me know if you need tips on how to use it.

PH

Patrick,
Thanks, will do. I am probably several weeks away from getting to the brakes. Waiting for the trailing arms to be returned from Bair's.
Ed

[Patrick H.]

Re: bleeding brakes on C3

No problem.
Especially available on Wednesdays for consults.

[Terry M.]

Re: bleeding brakes on C3

No problem.
Especially available on Wednesdays for consults.

How much is the co-pay?

[Tim S.]

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

This is a great point. That's why I'll clean out the M/C reservoir as best as possible, and then do a gravity bleed. Prime opportunity to have a beer