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Post by ondirt29 on May 7, 2022 18:53:15 GMT -6
I've built a new car 1985 Chevy Monte Carlo. I run Power Brakes before and had no problems. (I enjoy the ease in braking. Beside my rules demand master cylinder must be on fire wall.) But this time, I have all new lines front and rear disc brakes, master cylinder. I did what you suppose to do. I bench bled the Master cylinder, bled all lines, bled all brake calibers I've done this four times. But the brake pedal still goes to the floor. I have even used a pressurized brake bled the system. But the brake pedal goes to the floor with and without the brake booster (engine running). I'm at my witz end. Everything is new. The only thing I haven't tried is bleeding the brakes backwards. Does anyone have any real suggestion?
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one8
Fourth Place
Posts: 52
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Post by one8 on May 8, 2022 2:03:02 GMT -6
You're sure you have the brakes bled good and there are no leaks in the lines or calipers you may have a bad master cylinder. New parts can be defective. Look for a leak on the firewall, inside and out, where the master cylinder mounts. If there's fluid the internal seals are bad. Can you pump the pedal rapidly and get a firm pedal? After that does it slowly drop to the floor?
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Post by ondirt29 on May 8, 2022 9:04:09 GMT -6
Yep, I've done that. Made sure all the lines are clean and not plugged. Brake clean is use each time to clean the areas. No leaks. I have bench bled the master 4 times. I used both pressure, vacuum and working the plunger. I'm thinking the brake booster is bad. But even if it's bad, I should still be able to work the brakes. I get no caliper movement. What My next move is to use air pressure on each caliper to get them to move. Then rebleed the brakes. It's beginning to look like the Brand-new master cylinder is bad. I guess it off to Pull-a-Part to get a use one and see what happens. I don't know, I've run out of ideas.
Thanks for your ideas. You may be right the new master cylinder is bad. I'll let you know.
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one8
Fourth Place
Posts: 52
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Post by one8 on May 12, 2022 10:42:11 GMT -6
Sounds like that's what the issue is. The brake pedal should be hard to push when there's no vacuum applied to the booster. You may have fluid in the booster when you pull the master cylinder off. You can check the master by having someone push the pedal while you look inside. If the fluid swirls around when they push the pedal the seals are bad.
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Post by ondirt29 on Jun 4, 2022 16:57:18 GMT -6
Ok After a couple of days away from this problem with the brakes. I reattacked this brake issues. First, I adjusted all the push rods clearances of the master cylinder to the brake booster and brake booster to the brake pedal. All good. Then I took the portioning valve and made sure the valve was aligned. Done. Then went on to bleed the brake lines. I did this with vacuum and pressure. The vacuum I kept drawing air bubbles and air bubbles and air bubbles. So, I went to applying pressure bleed. I used a 60cc syringe. After 6 times I felt confident there should be no air in the lines. WRONG. Yep, I said WRONG. The vacuum tests kept drawing air bubbles. There are no fluid spots on the floor. So, I guess I will taking the rear brake system apart and testing each component. I'll keep you informed.
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