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I have replaced the master cyl. rebuilt the rear calipers bled them & so forth but i still have a very soft pedal I don`t seem to be getting all the air out. I have run at least 2 qts. of fluid through them trying to bleed them. I was unable to get 1 bleeder screw open. Could this be my problem? I don`t want to spend $300 or $400.00 needlessly. It does have power brakes. Any help would be appriceated. Thank you! Also I have a 63 conv. I would be interested in talking to other 63 owners @ cevette63@hotmail.com
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Re: brakes for a 1970
It sounds like you have done just about everything that you can. Have you replaced the brake lines? In addition, if you replaced any steel brake lines, there have been some discussions about stainless steel brake lines being to hard to properly seal with the softer cast iron. -
No Short Cuts-
You have to use all of the bleeders. If you snapped one off, it can be drilled out by a COMPETENT and very patient mechanic/machinist. It ain't easy to do without damaging the threads and/or the bleeder seat. The bleeder seat is not cut at the same angle as a standard drill bit: the mechanic MUST be good to avoid damaging the threads AND to avoid messing up the bleeder seat. All four calipers have to be bleed. If you have not replaced the brake hoses, be aware that they can look fine on the outside while they are deteriorated on the inside... causing the problem you describe. Some replacement steel lines may not seat properly when tightened, but these will leak and you will see brake fluid as a result. No fluid... no leak... not a factor. If everything above has been checked and found correct, including proper bleeding, then suspect a faulty master cylinder. Over the years, I have gotten both rebuilt and new master cylinders that were faulty right out of the box. But don't suspect the master cylinder until you are absolutely sure the rest is 100% correct. If in doubt about the hoses.. replace them. Also... I am presuming that your rotors do not have excessive "runout"... a condition that can introduce air into the system. If your brakes are firm until after you drive the car a bit, this may also be the culprit, or at least a contributing factor.Comment
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Re: brakes for a 1970
I should have mentioned that, in an attempt to remove the reluctant bleeder, I would use a good penetrating solution. I think that a product called PB Blaster is absolutely the best penetrant I have run across. Whichever one you use, try mildly heating up the caliper with a propane torch. I KNOW WHAT SOME OF YOU WILL SAY ABOOUT THE FIRE HAZARD! All I am talking about is passing the flame briefly over the area around the bleeder screw multiple times until the caliper gets warm, not hot. An alternative is to use a heat gun. Before the caliper has a chance to cool significantly, spray some penetrant (PB Blaster) onto the bleeder. The key here is to make the caliper very warm, definitely not hot. After the initial warming, I would spray penetrating solution on it twice a day for a couple of days. Then I would use a six-sided socket and very gently try to remove the offending bleeder. If you choose to not use any heat, the penetrant should still work, but not quite as effectively. I have used this technique on some rusty parts on my 66 with great success. Patience is the word here, though.Comment
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Re: brakes for a 1970
C.E.,
I replaced a bad caliper with a rebuilt once and had no peddle. These calipers are not only hard at times to bleed but can be leaking internally and give a poor or no peddle. Chevy manuals say to tap the caliper with a rubber mallet while bleeding them to remove all the air. You may also have a weak master cylinder. Hope this helps .Comment
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