Fire.....well amost

[sermis]

The brake system is fried, no really fried. My son was pulling back into the house and the brakes were kinda "squishie".
He parked the truck and opened the hood and then saw sparks coming from the area of the master cylinder and then the brake lines got red hot. The front brake line from master to caliper melted into. He said one of the rear brake lines is now dripping too. I'm guessing it got voltage into the brake system but from where?

 

[Bravojmc]

Major short...? Never heard or seen anything like that!

 

[infidel got me]

Ground takes path of least resistance. It will fry your clutch cable on a vw gti if electrics are not grounded properly. Ask me how I know.... Or a hot wire hit a brake line/master cylinder.

 

[Wire Fox]

The brake system is fried, no really fried. My son was pulling back into the house and the brakes were kinda "squishie".
He parked the truck and opened the hood and then saw sparks coming from the area of the master cylinder and then the brake lines got red hot. The front brake line from master to caliper melted into. He said one of the rear brake lines is now dripping too. I'm guessing it got voltage into the brake system but from where?

Exciting! ...in a really awful way.

I can't really answer exactly where it happened, but it seems clear to me that a positive wire short-circuited to your hydraulic brake line. The brake line can easily contact chassis ground and it's likely its normal condition, so as soon as one of the positive cables somewhere contacted the line, it would have completed the circuit and formed a short circuit. This diagram out of the TM should be able to help you start you diagnostics, since it shows where the metal hard lines run and may make it easier to trace the brake line and find that short.



Just based on where you saw all the sparks and excitment, I almost wonder if your alternator failed and started producing a voltage high enough to create an arc? I really don't know how probable that could be for it to produce a high enough voltage to arc that size of air gap. Did the sparking stop when you stopped the engine or when you pulled the battery?

 

[Wire Fox]

Ground takes path of least resistance. It will fry your clutch cable on a vw gti if electrics are not grounded properly. Ask me how I know.... Or a hot wire hit a brake line/master cylinder.

...or this. I didn't think about it, but also check the grounds going from the engine and alternator to the main body harness/battery box. If those failed, it could have flowed energy from the engine bay through your brake lines. You're seeing first-hand why electrical diagnostics can be tough.

 

[TOBASH]

First check all engine ground cables. then check alternator ground wires. Finally check starter wires and stuff. Also check wires to batteries! They are old and if they short circuit they are attached to body and brake lines.

Only a few things have that kid of juice and are not on a fuse.

If this does not look simple then it will be faster and cheaper to buy an entire new wiring harness.

I feel bad for you and your son. Still, blame it on him and make him do all the family chores. (Silver lining)- just kidding.

IMHO

T

 

[sermis]

Well the answer is............THE STARTER FELL OFF..............go figure?

Anyone know where to get new hard brake lines? Even need the long one along the frame. I am just hoping that the calipers, master, and hydro boost didn't fry too.

 

[sermis]

And yes my Son was thinking and pulled the battery cable and started putting water on on the red hot lines to cool it off.
I'm sure it was exciting to see,. When I got home he was still excited....LOL

 

[juanprado]

Just a thought but how about the Cadillac valve or the time delay relay for the fan as both are close by? I know my time delay was all soft and gooey with epoxy running out. I have heard this can be an issue for fires/shorts?

 

[doghead]

Calipers should have been isolated by the rubber hoses.

 

[doghead]

Do they have a starter motor, end support bracket ?

 

[sermis]

Yes. I'm guessing the starter bolts snapped off then the entire starter turned and shorted out

Sent from my SM-G920V using Tapatalk

 

[sermis]

 

[sermis]

Both starter bolts snapped

 

[doghead]

So, they do, or do not , use a motor end support(like a cucv) as well as the 2 long bolts?

 

[Bravojmc]

How in the **** did that happen? Off road? Jumped it? Both bolts snapped?

 

[Bravojmc]

That didn't just snap off driving down the road.... I'd be asking questions...

 

[Wire Fox]

So, they do, or do not , use a motor end support(like a cucv) as well as the 2 long bolts?

HMMWVs do have a tail-mounted support bracket on the starter. Two versions, in fact. One is a straight slot and the newer version is more of a J-hook to help support the alternator while you install it. Sermis, did you have this rear bracket installed?

 

[Bravojmc]

Well if it didn't have the rear support and the weight of the starter and a big bump maybe...?

 

[doghead]

Vibration/harmonics, definitely could have been the issue, without the additional bracket.