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Yet another brake master cylinder question...


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Ok, first doing my final check before doing a test drive around the neighborhood. Brake pedal travel seemed a little soft. I popped the hood, and watched the reservoirs on the master cylinder while I pushed the brake pedal down (with the reservoir caps still in place). It's probably air, but it just looks like the fluid is trying to burp up in the reservoir. Repeats consistantly no matter how many times I stroke the pedal. I have bench bled the master before installing. Is there a chance I've got a clogged line and the fluid has no where else to go? Brakes will stop the car when pushed in and out of the garage, but I don't understand this large displacement of air/fluid in the reservoir. If I remove the reservoir caps and push the pedal, I'd have a mess. Any ideas? Thanks. -Rod

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Yes, bled the entire system after installing the master cylinder. Yes on having adjusted the pushrod. Stock aftermarket master cylinder. Both you guys mentioned the pushrod adjustment....maybe I don't have it set right. I've got roughly 1/8" of free travel on the pedal before I feel resistance.

 

I'm going to try and hook up some plastic bleed lines to the bleed screws on the master cylinder and pump fluid through the bleed screws back into the reservoirs to see if any more air exists, but I've done that setup twice already with no air coming through the bleed screw. -Rod

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yep...coming off a port on the back of edelbrock intake manifold to the booster. check valve is correctly oriented in vacuum line. I won't be able to get back on it until the weekend....I'll do a complete four wheel brake bleed one more time. -Rod

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Could be that you've lost a seal between the masters. When this happens you pump fluid from one reservoir to the other, but don't actually lose fluid. If this is the problem, you need a new master.

 

1/8" of free travel doesn't sound like enough. You need about that at the rod itself, so with a ratio of something like 4:1 on the pedal I would think that would be about 1/2" or so at the foot end of the pedal.

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Could be that you've lost a seal between the masters. When this happens you pump fluid from one reservoir to the other, but don't actually lose fluid. If this is the problem, you need a new master.

 

1/8" of free travel doesn't sound like enough. You need about that at the rod itself, so with a ratio of something like 4:1 on the pedal I would think that would be about 1/2" or so at the foot end of the pedal.

 

 

That may be it.....I'll pull the master back apart and see if there is any noticable damage/tears to the interior seals. Before that, I'll watch closely to see if the rear reservoir fluid level goes down slightly and the forward reservoir rises slightly, which would mimic what you say above. Thanks for the tip. -Rod

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