Need help--Brake pedal goes all the way to floor after several new parts replaced Options

[914xr75]

I posted a few weeks ago about leaking reservoir tubes under the gas tank. I replaced those and the leaking stopped. I bled the calipers, but did not bleed the master cylinder. This was the first time I had about 5% stopping power and the pedal went to the floor, not sure if you'd call it spongy, but there was no resistance. That was a couple weeks ago.

Today I replaced the master with a 17mm ATE, rebuilt one of the front calipers, replaced the front soft lines. The rear steel lines still looked good, so I left them. I bled the new master. It took about an hour of pushing out air bubbles, and two quarts of brake fluid into the system to complete the MC bleeding. Once done, the pedal was still pillow soft.

Now on to the caliper bleeding--I purchased the Motive pressure bleeding system. Pumped it up to 5 psi as recommended by Ian Karr. About 30 seconds later the Motive bottle was at 0 psi. There aren't any fluid leaks in the brake system. I replaced the reservoir seal and added Teflon tape to the fitting in the Motive hose. Still loses pressure.

I tried the HF bleeder you hook up to your compressor. For 3 minutes about 5% fluid and 95% air entered the bottle. About 8 ounces of fluid came out. That is where I left off after a full day of brake work. Then I thought, did I cross the reservoir lines? I don't believe I did that, and I don't think that would cause my situation.

Any help you can offer would be greatly appreciated. Sean

[914xr75]

Tonight's update. Pulled the tank again to look underneath for leakage. No leaks, but I jiggled the reservoir tubes and bubbles came up from the master. Finally located the pressure regulator, thanks
fiacra. Gave it some rubber mallet love.

Pedal cluster floor was dry. Took my time using the long tube method. Began the bleeding process once again. At the end I finally had a hard pedal. Hooked up the Motive to see if the system holds the pressure steady.

Pumped it up to 15 psi and lost about 2 psi every 30 seconds. This is light years better than yesterday. I could not locate an air vent or a overflow on the reservoir. Tomorrow I will inspect it with a microscope to find the vent and overflow. That is probably the last issue. I did put my ear up to the reservoir while the system had the 15 psi in it. I did not hear air escaping.

Had I not hooked it up to the Motive bottle, I would have thought the job was done.

[fiacra]

Tonight's update. Pulled the tank again to look underneath for leakage. No leaks, but I jiggled the reservoir tubes and bubbles came up from the master. Finally located the pressure regulator, thanks
fiacra. Gave it some rubber mallet love.

Pedal cluster floor was dry. Took my time using the long tube method. Began the bleeding process once again. At the end I finally had a hard pedal. Hooked up the Motive to see if the system holds the pressure steady.

Pumped it up to 15 psi and lost about 2 psi every 30 seconds. This is light years better than yesterday. I could not locate an air vent or a overflow on the reservoir. Tomorrow I will inspect it with a microscope to find the vent and overflow. That is probably the last issue. I did put my ear up to the reservoir while the system had the 15 psi in it. I did not hear air escaping.

Had I not hooked it up to the Motive bottle, I would have thought the job was done.

I think you have basically won the battle!! It is a PITA to get the air out of this system. Someone can correct me if I am wrong, but the vent is on the cap and therefore when you are using the Motiv the cap is off and the vent cannot be a source of pressure loss. Given what you wrote about that amount of pressure loss when the Motiv is hooked up and pressurized I'm more suspicious that there is a loose or leaking connection on the Motiv. Check those carefully, use a bit of soapy water to look for bubbles at the cap, on the hose and hose connections, and make sure the Motiv cap has the gasket in place and is on correctly. If you truly were losing that much pressure because of a leak in the system you would see fluid leaking somewhere. Once the Motiv is pressurized it should not lose pressure until you open the system. Even if there is air in the system the Motiv should still hold steady pressure. Be careful about how high you pressurize the Motiv. Some people have expressed concerns about possibly blowing connections at higher pressure. Not sure how valid a concern that is, but I keep it below 10psi to be on the safe side. I know some people bleed the system and then, as long as they have reliable pedal pressure, take the car for a ride on a bumpy road with the theory being this will dislodge the last of the air bubbles. A final re-bleed at that point should get rid of the last of the air. I know you have experience bleeding brakes so this point is probably well known to you, but if you have a solid pedal and pumping it does not bring the pedal up higher I think it is fairly safe to assume that you have the air out of the system. If you have a firm pedal but holding pressure on it causes the pedal to slowly sink to the floor, then you likely have a defective MC.

I've not used the long tube method before but I may also try it next time I have to do this. PMB refurbished calipers are on the shelf right now so that will be soon. Maybe I'll get the job done without wasting so much brake fluid. Dave is probably right that using more than a quart of fluid means that I'm not being efficient in my method. I need to have absolute confidence in my brakes so it may be that I'm overdoing it when I'm bleeding them (IMG:style_emoticons/default/confused24.gif) . In any case, brake fluid is cheaper than body work and way cheaper than surgery, a law suit, or a funeral.