[Jimbro727]

Update: Operating under the assumption that we made some sort of progress, since the pedal did seem stiffer, we bled the front brakes to ensure no air was there (and there wasn't any), started her up, and tested the brakes. They still feel spongey and too soft, BUT they do stop the car. Pushing the pedal to the floor (which is very easy to do), stops the car on a dime (I didn't take it on the road, but brought it up to 10MPH or so in my driveway. The car can now be stopped normally without putting the pedal to the floor - at about halfway down, I can bring the car to a normal controlled stop. BUT, the brakes still do not feel right. And I probably shouldn't have to put the pedal to the floor to stop the car quickly going 10MPH, I should be able to stop quickly from that speed before the pedal is anywhere near the floor (right?).

Thoughts?

Originally Posted by Shiny

Jimbro-

Sucks about the knee. Good to hear you are recovering enough to tackle your brakes again.

Mine are working well enough to tell me chipster probably has the diagnosis nailed, but I suggest replacing the rear cylinders before anything else. You said you tried that, but check the picture from Walt in this other thread and tell us which style rear cylinders you have ( I put it here too). So far, what I call the "evil cylinders" are proving to be a big part of this problem for at least me and another victim (Walt) who figured it out.

http://forums.maxperformanceinc.com/...d.php?t=598515

I had installed new or rebuilt rear cylinders when I first started working on my car. At the time, I had drums in the front. The drum master has a residual pressure valve built into it. The brakes bled fine and worked fine. I started having trouble when I went to discs in the front and replaced the master. Like you, I installed an aftermarket combo valve. When I started having trouble, the rear cylinders were the last thing on my mind. I wasted hours and money replacing everything else.

I ended up adding a residual pressure valve, which was a major pain, so go down that path as a last result. For me, it just confirmed the problem was sucking air through the rear cylinders when the pedal was released. When I am next united with my car, I plan to replace the rear cylinders with the NAPA style for peace of mind.

I was never convinced the aftermarket combo valves have any residual pressure function. I got 5 different opinions from 5 people. I know that mine does not have a check-valve at the rear port (the type valve used in the drum master). The disc master cylinder definitely does not have this function on the rear line. Most people must get away without it. I don't know for a fact, but I think your odds will improve if you use the NAPA style rear cylinders. I do know for a fact it is a cheap and easy thing to try before swapping everything else in the system.

Let us know which style rear cylinders you have....

Left is Walt's NAPA replacement, right is the style I have

Thanks!

My combo valve is from inline tube, so I'll call them and confirm if it does or does not contain a residual pressure valve. I actually did come across that thread after posting to this one. It looks like I have one of the "evil" cylinders, with the rubber on the outside. Did you find issues with many of these? Replacing that one cylinder (which was also an "evil" one), seemed to help, but I'm still having issues. What exactly was happening with these bad cylinders? Is it just that they're sucking air in through those seals? I don't get any air out of the passenger side rear, so maybe that one is OK and the driver's side is not? If I pump the brakes a few times and then pressure bleed the driver's side rear, I should be able to test for this, right? If I get solid fluid, then it's not sucking in air, if I get bubbles, it is.

And I almost went to NAPA to replace the driver's side cylinder on Saturday. DAMMIT!

EDIT: I just did some quick research on residual pressure valves, and it sounds like this could be my problem as well. Given my symptoms, what do you guys think? Inline Tube is closed right now, but if I'm understanding what the valve does correctly, if I crack a rear bleeder open, shouldn't fluid stream out since it's under 10lb. of pressure from the residual pressure valve?