I posted this in the general section but thought I would try here too, hope that's ok with the moderators. I've searched and can't find exactly what I'm looking for. 2008 coupe w/Z51. I removed the calipers to have them powdercoated by Mike (corvette pilot), great job by the way. Reinstalled them, and yes they are on the correct sides, all bleeder screws are on top. I also marked them before I shipped them to him. Tried pressure bleeding at 30psi like the shop manual calls for. The fronts flow pretty well, but the rears don't get a full steady stream of fluid that will fill the clear hose attatched to the bleeder screw like the fronts. It barely trickles out. I figured it should come gushing out at that pressure but it doesn't. Tried vacuum bleeding the right rear and with the bleeder screw open I actually created a vacuum, and the fluid came out very erratically. Put it all back together and the pedal was soooo soft. Got a helper, and manually bled the rears. Still, only got a small amount of fluid out each time before the pedal drops to the floor when the bleeder is opened. The pedal was a little better, but nothing like it's supposed to be. I plugged the brake lines when the calipers were off, yet some fluid still escaped, but not much. The rear of the master cylinder never ran dry, although I can't be certain about the front since you can't see it looking in the cap. I've bled many brakes on many cars before and never had problems like this. My questions are, even if the brake lines were to completely empty themselves while the calipers were off, which didn't happen anyway but, shouldn't I still be able to bleed them normally? Is it possible that the front of the master cylinder went dry, or are the baffles and slots designed in such a way that if the rear half had fluid the front would be at the same level? I've had master cylinders run dry before on other cars when you either are bleeding and not paying attention to the level or when I had a brake hose break and that did not require bench bleeding it, only new master cylinders when the lines attatched to it were disconnected. Or, on this car would the master cylinder running dry, if it happened, be introducing air above the abs components? If the abs is not engaged, wouldn't fluid go from the master cylinder past the open abs valves to the calipers like any other car, therefore normal bleeding should be possible? Does the ignition have to be on for some reason when bleeding to enengize the abs valves and allow normal fluid flow past the abs components? Still can't figure out why I got a vacuum on the right rear instead of steady fluid. Do you think I need to bench bleed the master cylinder? Do you think I need to get then right scan tool and bleed the abs system? Please help. Thanks.

 

I'm not sure where your problem lies Marc, but you can try a couple things.

-First, unbolt the rear caliper fluid lines and see if you can get anything to flow. If that works, then completely remove the bleed screws from the rear and see if fluid flows. There is a chance something is causing a blockage in the bleeder.

-Instead of pressure bleeding at 30 psi, start the car and bleed by pumping the brakes, putting full pressure through the system.

-Lastly, if something did go dry, you might need the dealer to use the computer to bleed them.

Hopefully someone else can offer something.

 

I do get flow by simple gravity. When I installed the first rear caliper, which was the right side, I connected the brake hose without the bleeder screw in the caliper and it started leaking. It was coming out of the hole where the bleeder screw goes, so I have flow. I of course then immediately installed the bleeder screw in that caliper as well as the other 3 before I installed them. I got all new brass washers so I don't want to have to remove a brake hose from the caliper at this point.

 

It's fixed! I am relieved. Thanks for all the input. I pressure bled again today at 30psi starting with the right rear, hardly a trickle with the engine off. Tried ignition on, same thing. Tried engine running, same thing. Pumped the pedal about 15 times with the bleeder screw open and the Motive connected (full of fluid, works great to keep the master cylinder full by the way), and got more flow. Did all 4 wheels in the correct order this way. Then did all 4 a second time with the engine off, all electrical off, and 30psi pressure only, no pumping. Started again at the right rear, very slow flow so I went and had lunch. Came out about 5 minutes later and to my surprise the Motive was down about an inch from where it was, and the bleeding hose into my bucket was full. Did this to all 4, went through over 3 quarts of fluid. Put it back together, and a quick test drive revealed a rock hard pedal, just the way it should be. The pressure bleeding with everything off certainly works, the rears just bleed much slower than the fronts. I think I just didn't give it enough time last time. Part of being able to do it this way though is putting the fluid in the Motive. Thanks to everybody for the quick help.

 

Glad you got it fixed!

 

Glad you got it fixed.

A note to anyone with a Motive power bleeder, I would not leave the car unattended with pressure in the system. I had the cap blow off with 25 lbs of pressure, and luckily I was there to relieve the pressure from the canister as it sprayed everywhere, put the cap back on the master cylinder and then flush all the brake fluid off the car with water from a garden hose. Also a good idea to make sure your roof is on and your windows are up. After I cleaned up the mess I placed towels all around the master cylinder in case it happened again. I must not have had the cap on all the way the first time but did not want to force it for fear of breaking the plastic tabs off that hold the cap in place.

 

1. Add brake fluid to the Motive Power Brake Bleeder tank.

2. Firmly connect the supplied adapter to brake master cylinder and pump the Motive Power Brake Bleeder to pressurize.

3. Starting with the furthest away brake bleeder valve (typically on the rear of the vehicle), open brake bleeder valve and purge the air and old brake fluid from your brake system.

For more info visit: http://www.buybrakes.com/motive