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#1
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I've been fighting a brake problem for some time now, and yesterday I think I fiqured out the problem is. I've got a 70 RR with drum brakes all the way around. 10" frt, 11" in the rear. When I take the car out after awhile Ill have pressure build up in the lines and cause the frt drums to engage. The pedal will get rock hard, and I will have to crack the both lines at the master to get the pressure off. I've replaced the master twice, the proporting valve, and all the brake hardware on all 4 wheels, and still it will build up pressure. I notice yesterday that the brake pushrod will not let the master cylinder valve return to it's rest position. I tried adjusting the brake light switch but I still couldn't get enough room for it come all the way back. I think my pushrod is to long. I got the car in 98, with no fender tag, or broadcast sheet, so Im guessing it's suppose to be manual brakes. Does anyone know what the proper length for the pushrod is, also has anyone used the adjustable pushrod from Mancni Racing I was wondering if that would cure my problem.
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#2
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Had the same symptoms on my '70. I could drive normally for about 1/2 hour and then the brakes would to apply themselves slowly until all I could do was spin the rear wheels. Let it sit for an hour and it was O.K. again.
Turned out to be a defective check valve in the "new" master cylinder. Every time I go to the discount auto stores I get burned! |
#3
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brakes
thinking back to my 70 bird mine was 11 at all 4`s.mine was manual. i have never found a spec in any manuals. see if you have a build sheet under your back seat that may help. if you pull the master from the booster will the master come back to rest. then it might be a bad or wrong power booster. the new booster is always supplied with a new rod. i hope this helps
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#4
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For starters your RR should have 11" brakes front and rear minimum,it could also have come with disc up front and 10" on the back if it had a dana or 11" if its an 8.75,seems like someone stole your 11" front drum setup or more likely they stole your disc brakes,anyhow your problem is VERY common,if indeed you had disc brakes originally the pushrod is a different length,this is true for Power disc brakes too,if youll go to a boneyard and retrieve a B body pushrod from a car with 10" front brakes everything will work ok,Ive also seen this prob when someone uses a drum brake master cylinder on a disc brake set up,the reason it hangs up after a short drive is in the outlet port of the master cylinder there is a residual check valve whichs maintains a constant 2-10 psi without any brake pedal being applied,this keeps the wheel cylinders from retracting so far,otherwise the pedal will go almost to the floor on the first stroke,but on a disc setup it applies the brakes enough to drag the car to a stop....PRO...
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