CP

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The problem is inconsistent brake pedal pressure after 2-3 laps at speed. Sometimes I've got a solid pedal at T1 (whatever track), and sometimes I don't. It varies from lap to lap during the same session, so I can't expect a pedal that is 100% there on lap 10 to be the same on lap 11.

At the end of the session, I ALWAYS am able to get 2-3 pumps of air out of my outside right front bleeder only (have used traditional and speedbleeders; same result). I was using Motul RBF600 fluid, and just recently switched to the Wilwood 570 due to price and the amount of this stuff I'm using.

The history:

I started having this problem just after I bought the car 3 years ago. It used to be a 1991 Mitsubishi Galant VR4 with stock brakes, 2-piston front calipers, one-piston rears, full (crappy) 2-channel ABS, track pads, new high-temp fluid.

I have since removed all ABS components, including the ABS unit in the fender and all the lines associated with that system. I've replaced the master cylinder with a new stock 5/8" unit, replaced the lines from that to a brand new non-abs proportioning valve, replaced the lines from the p-valve to the wheelwells, and used new stainless braided lines from there to the calipers. I've also installed a Stoptech kit that was designed for use in my car given my stock master cyl size.

So the entire braking system has esentially been replaced, except for the booster, but that checked out based on some tests for vac that I found online, and it shouldn't have anything to do with air getting into the right front caliper, or should it?

There are no fluid leaks, as I'd expect to have fluid shooting out of a pinhole at very high pressure, not sucking air into the line. I don't think the fluid is boiling, because I'm not having this problem on the left front. A caliper isn't dragging, as I've done some temp tests for that possibility.

At a recent event, someone suggested that my master cylinder may not be able to push the large amount of fluid into the caliper fast enough, creating an air pocket after a few laps. But this wouldn't explain why this happened before with the stock braking system. His suggestion was to get a larger master cylinder coupled with a manual Tilton p-valve.

Others have said to ditch the booster, go with a 1" master cylinder and a mechanical Wilwood/Tilton p-valve.

Any ideas on why this may be happening and what I can do to remedy the issue? In the meantime, I've become pretty good at left foot pumping the pedal coming into every braking zone. Even by doing that, my brakes don't inspire confidence and this issue is beginning to hinder my progression/learning at the track.

CP

I replaced the fluid reservoir and the lines from it to the master cylinder today. I'll report back after 2 days at NHIS this weekend if anything changes.