Ok, so for the past 3 hours, i've been reading all about heather's problems with her brakes, as well as everyone elses.  I've definitely got some good ideas of things to check, but my situation seems just a little (very) strange.

Vehicle rundown. 93 Sidekick 4-door stock running gear, 30" tires, 2" body lift, (rear ABS)

While driving around town, all the time on the roads, i don't have any brake problems at all and i would say my brakes work well, well enough that there doesn't seem to be anything wrong with them.

When i've gone offroad the last 2 times i've had a strange thing happen a couple of times.  Last month i was at Evan's with SnoFalls, and while waiting and watching him go up some ruts on an incline, my kick was just idling with the handbrake on.  Then my turn to go, so i'm in first low, then go forward a fraction and hit the brakes to take a better look, and the pedal goes straight to the floor.  Straight away i pump it again and the brakes are 100% there.  I drive thru the obstacle, get to the top, and the brakes are still fine.  About an hour or 2 later, i'm going downhill in a steep area, and i'm stopped for a second, and then it does it again, but i was hardly even moving.  It doesn't do it when i've "really needed to stop", yet!  So i brushed it off that there's something funny with the master cylinder or perhaps the booster, figuring that perhaps the vacuum was lost.  So for the next month while driving on road, it doesn't give a hint of trouble.

This past saturday up at reiter, i got myself in a bit of a pickle and was teetering on my left 2 tires, stuck in what can best be described as peat moss/top soil.  It was super super soft, and i sunk into an existing hole.  So i was stopped by the log under me as well as the dirt holding me still.  I sat there and idled for about 30 seconds (with the handbrake on, even though i wasn't going forwards or back), then i hit the brakes to release the handbrake to be winched back and the pedal hit the floor.  Now the last time it happened, the next time i hit the pedal the brakes were right there.  I hit the pedal about 4 or 5 times slowly to the floor and nothing happened (felt the same as flushing fluid out of the system with a bleeder open).  Once again i was thinking "vacuum brake booster", so i hit the gas to "increase vacuum pressure" (all of this is me trying to figure out WTF this thing is doing), then the brakes were fine, thank goodness.

I jumped out before we proceeded with the winch to check for leaking brake lines, and didn't find anything, and none of the lines were overextended or hung up on anything.

I got unstuck, and long story short, drove home just fine. 

I got home, checked every brake line, pulled and tugged on them, and not a sign of a leak.  It felt like i had completely lost brake pressure thru the fluid.  My fluid level has maintained full since before Evan's with no signs of leaking.

So there's what's happening.

I'm going to pull the rear drums this arvo to check the tensioner, springs and shoes and see what's happening.  I'm wondering if maybe the wheel cylinders are not staying pressurized against the shoes on the off chance (but how could that happen).  Could they retract themselves, requiring the pedal to have to be pumped for them to push out?

Each time this has happened, the hand brake has been on, so the shoes are out against the drums, which is strange for why i am having any problems.

It's so hard to diagnose something that's not visual, like a leak or something broken...

So anyone else had the "pedal to the floor" problem???

that is definetly wierd, but I think you might be onto the "handbrake causes it" ...

what if a spring was broke/disconnected, the cable brake would extend the shoe, but the brake cylinder doesn't go with it (due to missing/broken spring) ... a few pumps and the cylinder gets back ...

Thing is doesn''t explain why the fronts wouldn't hold ya ... unless they are worn or wet or ...

It's for sure wierd.  Guys here at work reckon booster or master cylinder.

The brakes were definitely not at all wet when this happened the last time.

I think if it's not the rear brakes, then the booster or mast. cyl must be going crazy.

What i was thinking is perhaps if the M/Cylinder has a failing valve/seal, then occasionally at strange angles (aka offroad), the fluid pushes right past the seals when i apply the pedal (not giving me any brake pad pressure), then somehow it works ok again??

I figure if the rear wheel cylinders aren't contacting as far as they need to contact, then all pressure from the system will go to that specific area before any of the brakes work.  But wouldn't a proportioning valve stop that from happening so i still have front brakes?  Especially since front brakes engage before the rear brakes do.

My car is a wierdo.

This is a weird one....

      A thought to check....are you running a header or have you removed the manifold heat shield?
It almost sounds like the brake fluid is boiling. Extended idling might cause the heat to rise into the
resevoir.....hope it helps.

Zag

No, stock exhaust with heat shield.

I do have a fraction too much brake fluid in the reservoir, but i don't think that would give me problems.

I guess it wouldn't have hurt to check the temp of the brake fluid.  I need to flush it anyway as it isn't clear, but it's not filthy.  It may be getting too hot perhaps.  You'd think it would do it on-road as well though.

If its all stock I wouldn't think it would do it.

With no shield I thought it might because of no airflow allowing it to heat sink.

But the fluid could be contaminated.

Zag

So i haven't had any time to look at the actual brakes yet, but i checked the fluid again to make sure it's still full.  it's full alright, but it's the color of coke.  I'm wondering if it's that color now because there is some mild leak that's letting dirt into the system, or if it's from just being old and getting hot.

It's time to flush the fluid all out, and see if that makes a difference.  It's just a PITA doing stuff like that, then it not making a lick of difference.  The several times i've flushed all the brake fluid out of a car it didn't make any difference....

comments on brake fluid causing these problems?

I had this problem too, It was my rear brake shoes were worn beyond belief. combined with a leaky axle seal they didnt' work well at all. Replaced the shoes for the time being and problem solved.

Thanks, that's good information.  I'll take a look at it asap.  let's hope it's that simple.  M/cyl's are expensive for my fo' do'.

I was off reading a different post about the hagen widening thing and found this line in the post...


<<With all that being said, there is one side effect. Steering bump-stops have to be adjusted properly. Improper steering adjustment or if you bend a front-end part, (tie rod, drag link, Idler arm) and the steering is allowed to turn too far, the caliper may turn so far it runs into the coil. This forces the piston back in the caliper and you wont have a brake pedal until the second pump. >>

I didn't think about this before, but my wheels were turned full lock this past saturday when i had no pedal.

So the caliper could perhaps be touching the coil (i never thought this was happening) and the piston then goes back into place??  I guess i need to pull the wheels, turn lock to lock, and see what the hell is happening under there.  I can adjust out the steering bump stops to prevent this, but why is no one else having this problem?  Maybe it only happens at full down travel, with the tires turned.  Mine was at full down travel, with OME shocks, and turned to the right. 

Also, i'd never read that hagen widening article before...