Brakes on Fire!!!

[98 HOO]

'04 DII with 80k miles

A couple miles from home this morning - I went to stop to make a left and the brake pedal went to the floor - no slowing down. Luckily no one in front or beside me so I veered back into the straight lane and continued on. Turned around and went home slowly using emergency brake when needed. Got out of the truck at the house and looked back - both rear brake lines and wheel sensor cables were on fire!!!!
Pulled the extinguisher out of the back of the truck and put them out. Within seconds, both burst back into flames. Repeated this extinguish/catch on fire again, then grabbed a wrench and disconnected the battery - ran to garage for second extinguisher and put out the fire again. Fires stayed out that time..

So....I am fairly certain this is electrical. Somehow the wheel sensor wires are getting too much current causing them to heat up and catch on fire. Once they were on fire, they caught the brake line's plastic coating on fire and burned through those so I lost pressure.

I don't know what to look at that would be causing this current to get to the wires. What should I check first? Searched the forums and didn't see anything else similar - anyone else had this issue? Thanks for the help/suggestions.

 

[WILL.TILLERY]

any chance they were rubbing up against your exhaust anywhere?

 

[98 HOO]

I do not believe so - these fires were at both wheels, very near the calipers on both sides. Even the drivers side location that was on fire was about 18" from the exhaust.

 

[ptschram]

The wires in the ABS sensors aren't really big enough to cause that much trouble, I'd expect them to fuse before they could catch fire.

I suspect there was something else causing the heat to be generated and the brake fluid was what caught fire.

I'm with Will, I think it was an exhaust heat issue.

 

[98 HOO]

Thanks for the input -
I do not think it could have been exhaust because both sides caught on fire - only right where the cables loop down to connect to the hubs/calipers. The passenger side, where it caught on fire is 4' - 5' away from the exhaust where it repeatedly burst into flames.

Perhaps both rear calipers stuck and that caused the heat in the fluid that caused it to flame? I don't think I would generate that much friction heat in such a short distance without noticing the drag though. I also don't know why it would repeatedly burst into flames until I disconnected the battery.

 

[enjoi1968]

whens the last time you changed brake fluid?

 

[98 HOO]

About a year ago I did a substantial flush at each wheel (two bottles of DOT4 through it), but did it by pumping manually - not with testbook turning abs pumps on.

 

[chemtool]

stuck calipers? That must have been a sight to see...

 

[98 HOO]

I don't think there is much of a chance of both calipers failing at the exact same time, but I could see there being an issue with the ABS modulator causing both brakes to stay engaged??? I was thinking electrical only b/c of it reapeatedly catching fire till battery was disconnected.

 

[p m]

stuck calipers? That must have been a sight to see...

Happened to my old 89 Classic. Took me across two lanes on the freeway....

 

[brian4d]

I've heard of stuck calipers before (at night) and the owner claimed the pads were glowing red. Not sure how much truth this holds and what material the pads were.

 

[chemtool]

I've heard of stuck calipers before (at night) and the owner claimed the pads were glowing red. Not sure how much truth this holds and what material the pads were.

Sure they can get red hot and if you have a leaky hub / o'ring and gear oil mixed with brake dust caked around the pads they will start on fire right quick I would guess.

 

[98 HOO]

Sure they can get red hot and if you have a leaky hub / o'ring and gear oil mixed with brake dust caked around the pads they will start on fire right quick I would guess.

The brakes themselves were not on fire, just the brake lines and the Sensor wires on both sides, and only between the wheel and where the abs wire plugs in to the main wire and the flex line is plumbed to the rigid line.

 

[gmookher]

both sides???

 

[98 HOO]

Both sides - it was crazy. Only b/w wheels and wheel well.

I will replace lines and Sensor cables, but I wish I knew what caused it. Guess I could have someone connect the battery while I hold the existing burned cables and see if they get hot. Better to test on the existing than replace just to burn up again. I just don't know from where those wires would get that kind of power thrown to them. If they don't get hot, perhaps something with the master cylinder/ABS module had the rear brakes locked down. Hard to believe I wouldn't have noticed that for couple miles - I was gettin my normal MPG per the scanguauge, so I don't think they could have been locked....

 

[gmookher]

I'm with the others, I doubt the current in the sensor wire did it, but its so freakish for both sides, nothing else really makes 'sense..'

-subscribed-

 

[Blue]

what kind of pads are you running?

 

[98 HOO]

Cheapo pads (Advanced Auto) on EBC Sport Rotors. Pads have been on for about 10k miles.

 

[gmookher]

note to self: avoid advance auto Cheap bastard pads

 

[clarkwjackson]

While you have everything apart check your calipers. Make sure the slides are in good condition etc. Weird it was just the rear brakes...