Bleeding Brakes - Can't Get Any Pedal Pressure Options

[ThinAir]

Well, I've searched, but there are so many responses about bleeding brakes that it's almost impossible to sort through them... so I'll ask.

I replaced the front calipers on the '70 with a pair of those pretty ones from Eric. When I put the car up on stands for the job I had good brake pedal pressure. Now that the new calipers are installed and the lines reconnected I've bled the brakes. I blocked the reservoir vent. I use a Motive Power Bleeder.

I'm sure that I'm not getting any air out of the bleeders at the wheels, yet I have no resistance when I press the brake pedal - it just goes straight to the bottom.

It seems unlikely that the MC would go so suddenly, so I'm wondering what else it could be.

As always, this is work that is being done last minute to get my son's car ready for this weekend's Route 66 Ramble. Despite lots of trying, things never seem to get done well ahead of time!

[Krank]

The first thing I always do when doing hydraulic brakes is: remove all bleeders and take a small drill bit to clean out the bleeder ports. the little suckers always have a bit of rust slowing down the release of fluid, just enough to make bleeding difficult. I prefer the pressure bleed technique and when doing so always start at the furthest wheel. When bleeding the cylinder connect a clear plastic tube into a glass bottle and watch the flow to check for any signs of bubbles. When I have fluid flowing I swiftly open and close the bleeder to keep the air compressed and traveling towards the bleeder port. This of course is after all necessary components have been checked and replaced/repaired as required. One quick method of diagnosis is to isolate the front or just one wheel from the rest by gently pinching the brake hose to the closest wheel or set. This also works to test an existing cylinder/caliper by applying full pressure on just an old/weak location as pressure will seek the weakest point. Sure enough as soon as you have replaced/repaired a couple of wheels the third or fourth one springs a leak a short time later. You should be able to "pump" up the brakes and get some kind of pressure or resistance but if there is any air present the pedal will feel spongy. Once you have some pedal pressure, press and hold the pedal down to see if you can maintain pressure in the system. I usually hold it for as long as the blood remains in my leg. This will indicate a bypass in the master if the pedal slowly creeps down. It usually occurs in the "normal" application zone of the master where most of the wear occurs in the bore.