I flushed my brake system with new high-performance fluid and although the brakes are just as stiff as they were before when they're cold, they get a lot stiffer when they're hot.

I noticed this all of the sudden during stop-and-go traffic during when suddenly it started braking a lot harder than it did before.

I seemed to have a problem with the rear calipers having small air bubbles coming out of them no matter how many times I flushed them (maybe I had the valve open too long?). But if you have air in there and it gets hot, they tend to get stiffer, right?

Or maybe my brakes were dragging or something?

I'll check them in the morning when they're cold, and see if the stiffness went away.

I'm 90% sure there was *no* air in the front calipers (or at least I was able to get all new fluid in them before I ended up letting air in).

 

do you mean the brake pedal was getting stiffer or the brakes were biting harder?

 

Both... but only after about two hours of highway driving (and a serious traffic jam).

 

How did you bleed the brakes?

How do the brakes feel today?

 

I bled them the old fashion way (two-man job with an 8mm wrench, a hose, and a bottle).

I haven't checked them yet... I'll do it...now, I guess.

 

Hmm... they're still biting just like they did last night (meaning hard), but they're also squealing a little bit. I don't know why... the pads still have plenty left.

Also, is it normal for the pedal to feel like it's hitting a stopper or some kind when you press on them hard? If I pressed nearly that hard, I'd have locked up my brakes ages ago, but it still feels kind of strange.

The pedal still isn't as stiff as I'd like it...although it bites plenty hard.

(maybe I over-adjusted the pedals and the rod is hitting something? It's been like this for months though...)

 

So all you did was ONLY change the brake fluid?

If you are able to stop the car, then I would just take a look at the your pedal adjustment. Its possible for those nuts to come loose and cause some problems.

To check and see if your pads are dragging, do the "coast test". Basically, get the car going about 40 mph and take your foot off the gas. If the pads are dragging, youl'll feel the car slow down much quicker than it should.

 

I think the reason the brake bite harder now is because there might have been some air in the rear brakes to begin with (probably caused by me causing them to drag and overheat after changing the pedal settings one time). They probably started biting harder as soon as I bled them, but didn't notice it until I got into heavy start-stop traffic. (either that or there is still air in the lines, just not as much as before)

I'm fairly sure they aren't dragging because when they do, they tend to get extremely hot (rather than just a little warm) even after a short drive. (I did it before)

Expecting a stiffer pedal may just be me asking for the impossible to satisfy my preferances (outside of installing steel braided lines and a master cylinder stopper, that is), and I probably should have never adjusted the pedals to begin with (the instructions in the FSM are too vague when it comes to free play), although the pedals were a little high (I wanted more legroom...).

But besides being just a little squishy (yet still biting hard and NOT sinking or something), the only thing I really think I need to worry about is whether or not the power piston is bottoming out or something. Probably not, since I think the pedal went all the way to the floor when we were bleeding it (but I didn't confirm this myself).

I'm not sure if squishy is even the right word for it... I just want them to be firmer. It's really only "squishy" when I'm sitting still and pressing on them hard, or applying extremely hard braking while driving (more than enough to lock the brakes).

 

exactly what kind of brake fluid did you use?

i would definitely take another look at that pedal.

 

what your describing sounds pretty normal in a boosted brake setup.... the pedal feel will not change dramatically even if you had a little air in the system however the the force transfered to the caliper piston will increase = more bite sooner so the pedal will feel more sensative when driving but while sitting still and pushing on it it will always feel soft.

 

Castrol Synpower... not exactly racing brake fluid (seeing as how it costs 1/20th as much), but it's definately better than the generic stuff I put in it.

I can't see that there would be a problem with the pedal itself, just with the adjustment.

The FSM adjustment instructions are very vague... for free play it says "until the valve plunger contacts the stopper plate = until the power piston begins to move," but WTF does that mean? If you adjust it in too much, the brakes drag, and if put it out too much, well, I don't know what happens. I would imagine it wouldn't stop as well.

But if you're standing still, should you be able to feel it hitting a stopper of some sort when you push it in? Or does that mean the master cylinder is getting bottomed-out?

 

assuming it's talking about what i *think* it's talking about:

it's "out" too much, there will be some dead play at the top of pedal (which is normal).

if it's "in" too much, it will effectively squeeze the brakes a bit.