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Re: C2 J50: Yikes! No brakes...
Dan------
You need to do the following:
1) Bench bleed the master cylinder;
2) Check the rear AND front rotors for excessive TIR (total indicated runout). Anything greater than .005" TIR is too much. .002" or less is preferred. The front brakes can experience excessive runout just like the rears, especially if the hubs have been seperated from the rotors for rotor replacement.
Your symptoms sound like the classical air pumping syndrome caused by excessive TIR on the front and/or rear rotors.In Appreciation of John Hinckley -
Re: C2 J50: Yikes! No brakes...
The rear hubs have never been apart as they still have the original rivets in place. Is runout still possible if the units have never been separated?Comment
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Re: C2 J50: Yikes! No brakes...
Dan-----
Yes, it is. Although far less likely if the rotors have never been seperated from the spindles, it can still occur for a variety of reasons.
You need to dial indicate your rotors to determine just where you're at. If they're ok, then you eliminate this possibility and you move on to the next thing.In Appreciation of John HinckleyComment
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Re: C2 J50: Yikes! No brakes...
Dan - If after you check as Joe suggests, I would have the rotors and spindles turned on a lathe to maintain the accuracy, instead of separate. You may have to go outside your typical auto machine shop depending on the shops tooling. There are centers on the spindle that allow perfect centering in a lathe, the same centers that GM used...CraigComment
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Re: C2 J50: Yikes! No brakes...
Still have one question unanswered; I'm unclear why if one "set" of brakes (rear OR front) fail on a dual MC system, why/how both would fail. Just thinking that the odds are slim that there is a run-out problem with both front and rear, but perhaps so...
Symptoms seem to point more toward a MC problem, right? Firt order of busines, as Joe suggests is to bench bleed first, then move on...Comment
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Re: C2 J50: Yikes! No brakes...
Dan-----
The front and rear systems are definitely completely seperate. For the "air pumping" phenomenon to occur, BOTH systems would have to have at least 1 rotor which was out of spec. That is not so unlikely, though. It can happen for a variety of reasons. The only way to find out if this is the source of your problem is to measure them, and that's exactly what I recommend doing first.
The symptoms that you described are much more typical for an "air pumping" problem than a master cylinder problem. In fact, I'd say that the master cylinder problem is far less likely given the symptoms. However, I originally suggested that you bench bleed the master cylinder first since you really should do this anyway for several other reasons. So, you might as well get this out of the way for GENERAL reasons. I don't think that it will solve this problem, though.In Appreciation of John HinckleyComment
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For those that have never experienced
a brake system failure, please do not expect miracles when one half of the system goes down. I lost my front brakes due to a pin hole fretted through a brake line. The miniscule amount of braking power offered by the rears, and the extremely low pedal position was a real eye opener- and pants filler.
Luckily, I was very close to home and had a new line installed within hours. This was the day AFTER I returned from a 5000 mile road trip to Galveston Island.Comment
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Re: For those that have never experienced
As Mike says, a failure in one system will make you think both have failed.Comment
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