I own a 99 "Trail" Blazer 4wd. My wife was driving it home and heard a grinding noise and there was smoke coming from the drivers side front when she got home. I took it out later that night and could not reproduce the issue. After driving for several days it happened to me, but only when it was over 75 degrees out. Wheel appears to lock up, and smells like overheated brakes along with the wheel itself getting scorching hot. I first replaced the front pads and rotors and the drivers side caliper and bled the brakes. Still happened. Having replaced the passenger side hub and bearing already I replaced the drivers side next thinking maybe it was heating up and locking up. Still happening. I have been doing some research and have seen suggestions that it could be a kinked or collapsed brake hose, but I see no evidence of this on the outside of the hose. Has anyone experienced something similar to this or have any thoughts as to what the issue may be. Is replacing my brake hose the next step? When up on jacks the wheel appears to move just as freely as the passengers side but I have noticed when I come to a hard stop and release the brakes the vehicle does not want to move on it's own unless I give it a little gas, if I just tap the brakes and then let off it will coast.

 

The inside of the flex hose is what collapses, there is nothing visible. When you apply the brakes, hydraulic pressure forces the fluid to the caliper. When you release the brake, the pressure equalizes on its own, (less than a second). If the hose is collapsed, the pressurized fluid gets trapped in the caliper, keeping it applied. As the fluid seeps past the restriction, the pressure is released, and the caliper piston retracts back into the caliper. The most common causes for this to happen are: brake fluid contamination, (trans fluid, motor oil, etc) and not supporting the caliper when it's unbolted from the mount, (never let the caliper hang under it's own weight). Another possible cause is the hose was twisted when the caliper was reinstalled. If the fluid was contaminated with transmission fluid, all rubber parts in the hydraulic system need to be replaced, ie all flex hoses front and rear, master cylinder, (including the reservoir and cap) ABS unit, and all 4 calipers.

 

Thanks for the quick reply. I bought a new hose last night but didn't have a chance to install it. I found some more info suggesting to pump the brake pedal about 20 times, and see if the wheel is locked up, if it is open the bleeder valve and see if the caliper releases. If it does it's a collapsed or kinked brake hose. Does this sound correct? I plan on replacing the hose either way, but it would be nice to know that I have finally addressed the issue, it's also possible I would imagine that the hose got damaged because of the heat. I really don't know what the root cause was and what was damaged due to the heat of that. The hub did have to be replaced anyway as it was much harder to turn then the new one and also the sensor wires going into it were all melted (although no actual wire was exposed). I also do not believe that anything other then brake fluid was ever introduce to the system.

 

Pumping the pedal and opening the bleeder is fine, but if the pressure has equalized before you get the bleeder open, the test is not conclussive. (It will also cause air to be injested into the left front hydraulic circuit.) Another thing you can try is jack up the left front wheel, engine at idle in park or neutral, (the wheel should rotate freely). Have an assistant apply firm pressure to the brake pedal while you attempt to rotate the wheel. Release pressure on the brake pedal and the wheel should immediately rotate freely. If not, chances are the flex hose is collapsed.

If it's only the driver side that hangs up, the problem is not the master cylinder, but it could be the ABS unit, a hydraulic line to the front left, (steel or flex) or the caliper itself.

 

Your hose is bad. Period.

 

I agree with an internally collapsed hose. You can't tell they're collapsed. Just replace it. It's a very simple job and will at least give you peace of mind that the hose is ok. I'd replace the other side, as well. Just as a precaution.

 

Finally got a chance to work on this, the truck has just been sitting. I replaced both hoses on Monday and have been driving the truck with no issues since then. Thanks for the input everyone.