Brakes won't bleed out

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Jul 10, 2017 | 06:02 AM

Rev Ron

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Brakes won't bleed out

I'm restoring a 70 that I have not driven yet. It came with a lot of new stuff, including the Power brake booster, brake master cylinder, brake lines and brakes. I've installed a new proportioning valve. However, I can hardly get the front lines to bleed out and am getting very little fluid to the rear brakes. I've tried to gravity bleed them the last few days and very little is happening. I've tried a hand pump bleeder. Nothing at all. This car has sat in my garage a couple years. I have no idea how long it sat before that, probably several years, too. Now with the fix. Yes, I bench bled the new MC. I think I did it well, but may need to do it again. What now? I'm thinking I should start with the MC, taking it off (again) and making sure it is not corroded, then bench bleed it, again. Step 2: disconnect al the brake lines and blow them out. What can I do to the 4 brakes to make sure there is no corrosion there after sitting so long? What other things should I do. I hope to gravity bleed them, but will purchase a Motive bleeder that so many brag about, if I need to.

Jul 10, 2017 | 08:52 AM

silver74vette

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From: Lakemont, GA

The best tool for this job is a pressure bleeder. But before that I would make sure that you set the booster push rod properly. If it is pushing on the MC you will not get fluid through it well at all. You want to set it so that there is about 0.030" of gap between the push rod and the MC.

Jul 10, 2017 | 10:49 AM

7T1vette

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From: Crossville TN

Have the rubber hoses at each caliper been replaced...or are they the original lines? The insides of those lines can deteriorate and get plugged. If those hoses look very old, replace them. That may not solve your problem, but they need to be replaced if they are decades old.

Jul 11, 2017 | 05:32 AM

Rev Ron

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SilverVette, thanks much. I hadn't even given thought to that. I will check it out. I've never done this before. I assume that I have to take the MC off some and set the gap from there? Or, is it done from inside the cockpit with the brake pedal? Obviously, with these questions, I have not taken a look at the setup yet and am setting in my recliner! Thanks.

Jul 11, 2017 | 10:20 AM

69Vett

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From: Austin Texas

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you can jack the rear of car to make the master cylinder level , this is the equivalent of bench bleeding the MC. I also use a rubber mallet to smack the calipers to release the air bubbles which stick to the inside walls of the calipers.

Jul 11, 2017 | 01:18 PM

silver74vette

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From: Lakemont, GA

Quote:

Originally Posted by Rev Ron

Yes you need to remove the master cylinder. The steps below are how I usually do it, they also make neat tools to measure the gap.

Remove MC from booster, make sure pedal is all the way up in the car (not partially depressed).

If you look in the booster you will see a push rod, usually these are threaded and capped with what looks like an acorn nut.

Gently put the MC in place and see if it seats all the way in the booster.

If the MC does not easily seat in the booster the rod needs to be adjusted in.

If the MC seats easily in the booster thread the rod out until it is just making contact as it seats (I usually adjust 1/4 turn at a time).

Once you have it set so it is contacting right as the MC seats I turn it 1/2 turn in and lock it in place.

Re-install MC and bleed.

Hope this helps, let me know if you have any questions, Chris

Jul 15, 2017 | 01:01 PM

Rev Ron

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Here is the rest of the story. I bought this car with a new power brake booster and new master cylinder on it, but never filled with fluid. I could not get it bled out... then discovered that the guy I bought it from had put the wrong master cylinder on it! It was for an automatic! The one for the automatic has a longer hole where the plunger goes in. Now that I've got the right MC, the car brakes bled out with no problem! Da!