Bleeding...

After I changed the brake plumbing between the combo valve and the booster, I spent a good deal of time bleeding the brakes, trying to get rid of the  spongy pedal.  No amount of bleeding the brakes seemed to fix the problem.  I began to question my bleeding procedures, my equipment, and then my sanity!

Worse than that, I took the car on a couple of test drives with mushy brakes.  This really wasn't very smart.  The pedal went almost to the floor... thank God I didn't really need to panic stop again!

The mushy brake issue really bothered me for a couple of weeks.  I kept going over every possible cause, and I just didn't get it... the car had a firm pedal with the old booster, and my original configuration with the new booster wasn't this spongy, so what was wrong now?  Logically, it didn't make sense to me that the pedal would be so mushy.  I started thinking that perhaps the master cylinder needed replacement, or the pedal ratio needed to be adjusted... but that didn't make sense either.

Finally, I considered taking the car to Tire Guy to have him go over the system and pressure bleed the brakes.  Sometimes, I just need help.  The idea of getting some professional help made me relax a little... then I had an idea!

It occurred to me that I might have done something dumb in plumbing in the new booster...

Here's the way the C490 came (the big guy on top).  Note the that it is configured to use the upper port on the outlet (green plastic plug), not the side outlet.  This is consistent with the C3400 below it, which uses the top port on the outlet.

When I plumbed the C490, I thought that using the outlet to the side looked  "cleaner" so I changed the configuration!  This was very poor thinking... it left an air pocket in the booster that can't be bled effectively.  Result: mushy pedal that no amount of bleeding would fix!

Replumbing the booster to use the top port, and then rebreeding the brakes (a lot) fixed the problem.  Now,  solid brakes!

I still don't know why pedal felt firmer when I first installed the C490 (between the master cylinder and the combo valve), but when I changed the plumbing around (so that it was between the combo valve and the front brakes) it must have let enough extra air into the booster that it caused this super mushy pedal.  

This has definitely been a learning experience for me.  I could say that the key lesson here is about air pockets in brake systems, but I think it is more sublime than that.  Here are some key thoughts:

1. If what I am doing isn't working after I have given a complete and honest effort (like bleeding the brakes), then doing more of it probably isn't going to help.
2. If I am agitated, upset, or downright mad, I am unlikely to make a good decision.
3. Experience trumps logic.  I can think my way into all kinds of wrong answers.
4. It is OK to ask for help... and sooner is better.  Once I come to that point, I am probably going to calm down and think more clearly

It's funny how I have to learn this lesson over and over again.