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Thread: Booster pin pre-load?
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02-19-2011 #1
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Booster pin pre-load?
I have C5 brakes with CPP booster/master/prop valve for disc/disc. I believe its a mid 70's style corvette master. The brakes are dragging slightly. When I slide the boster pin into the booster, it feels lke trapped air behind it and it keeps the pin from sitting all the way down. Is this for preload, or could it be the cause of the light brake being applied to the master? Hope this makes sense. I am going to unbolt the master & see if it releives the drag. Will take some pics.
Scott
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02-19-2011 #2
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Here's a pic. As soon as I removed the master all 4 wheels spin freely. This pin will go another 5/8" further into the plug, but the trapped air keeps it pushed out to where you see it in this pic. If I shorten the pin I am afraid i will have too much travel in the pedal. Is the trapped air designed to give pre-load? This is my first time running into this.
Scott
02-19-2011 #3
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yes, what happens when you un-hook the rod from the pedal? If there is no change it is in the booster assembly, then I would contact CRP, If you modify or cut something you will not be able to return it.
vinceMrQuick ΜΟΛ'ΩΝ ΛΑΒ'Ε
02-21-2011 #4
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The booster pin has an o-ring on the end, trapping the air in and preloading the pin on the master. Can I remove the o-ring? I put the pin in the master, then slid on the booster plug & pushed it on until it bottomed. The preloadis enough to move the master piston before you overcome the preload, if that makes sense. Scott
02-21-2011 #5
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Usually the pin is adjustable. You want .020" clearance between the pin and your master cylinder piston. You can remove the o-ring, its just there to hold it in place, once assembled everything should self center. I would check your clearance you may have to grind the pushrod for clearance.
The tool for checking clearance looks like this. http://www.mpbrakes.com/uploads/prod...2003_large.jpg
Here is a how to using mostly standard tools http://aarc.epnet.com/autoapp/8266/8...USHROD_ADJ.htm
Let us know what you find
Donny
02-21-2011 #6
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I took the O-ring off and test fit. Much better without the o-ring. Had to grind off about 1/2 of the nipple on the end of the pin. I used a telescoping pen magnet as a mockup pin & shortened the pin about a 1/16 shorter than my test pin. Have not driven the car yet but the pedal is good & wheels spin freely now. THANKS
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