07 LT Stepped on brake hard, Hard Stop. Then after pedal felt weird, soft and low. Checked for leaks, checked fluid. Car stops but way to much pedal travel. Recent pads and rear drum servIce, still feels adjusted well. Little Ebrake travel and can firmly stop car with it. Pedal varies, stiff, soft, hard, long travel, short travel, some change with RPM idle as well as acceleration. I am leaning towards booster? Or weak master pulled air under hard braking? Any ideas?? No code or lights still driveable but questionable. Help Please.

 

My guess is you blew a seal somewhere.

What does brake "service" mean?

 

Probably we can interpret a rear brake "Service" to mean cleaning them, and snugging up the non-self adjusting "self adjusters", which as we all know Don, have been an HHR bugbear since day 1.

I'm thinking FMHHR has one of three possible things going on...

1. A duff brake booster, which can give itself away by "vanishing" brake fluid and a smoky exhaust if the internal seals have gone.

2. Air entrained in the system, which means bleeding the brakes again.

3. When the rear brakes were done/serviced, the adjusters weren't adjusted properly. And being that the rear drum are mostly responsible for the "feel" of the brakes, they could be the source of the odd pedal travel and feel.

 

IF cleaning and adjusting was what was done; I would be suspecting a blown rear cylinder as a strong contender.

Worn out shoes that are called into emergency service can over extend the pistons, that does not affect the E-brake.

I was amazed at the difference new rear brakes (shoes, hardware and cylinders) made even though the shoes looked good and were within spec at 150,000 miles.

 

Dang straight Don, there was plenty of "life" left in the rear shoes on my '06, and they were properly adjusted. But when I replaced them with a fresh set of Raybestos HD shoes, and took it for a test drive, my first thought was "this sucker really stops now!".

And the pedal feel improved by quite a margin.

 

Mushy brake flex hoses, could be the problem

 

Also a good point Oldblue, but in my experience, mushy flex lines tend to act like one way valves.

You can apply the brakes normally, but the pedal returns very slowly as the flex lines restrict the return flow of brafe fluid to the master cylinder.

Many, many, moons ago. We had an LTD come into the Firestone store where I worked, when you stepped on the brakes, they wouldn't release for ten minutes until the fluid snuck past the internal restrictions in the bad flexible brake lines.

 

I'll share an experience I had with my Lumina APV last year. Different animal, but the same rear drum design. I had the same problem described by OP. When I took the rear brakes apart, on once side I found a piece of the adjuster missing (!) apparently causing inconsistent brake feel. Sometimes it was right there at the touch of the brake pedal, sometimes is was like, OH CRAP! New shoes, new hardware, everybody's happy in my case.

 

I like all the above suggestion.

Does the car have anti lock brakes? If so it is possible that a accumulator valve is not sealing properly.