Bad day for brakes and fires.

[mobileauto2000]

On the way to work my brake pedal got low all at one. I was only a block from the shop so I drove slowly and puled up to the gate with one hand on the parking brake. Sure enough the pedal went to the floor. I used the parking brake to stop.

After backing up to the shop I went under the truck and pulled down the brake pedal. I can tell that the piston in the master cylinder is stuck at the end of the bore. The fluid is full and clean. So I ordered a master cylinder rebuild kit and went to work.

But the truck was not through with me yet. One of the sales men came running into my office saying my truck was full of smoke. So we quickly drug the hose over and sprayed down the underside of the truck after I threw the battery disconnect . I found a small fire at the brake light switch. Some how the switch had internally shorted.

From now on I will be religious about the battery disconnect switch. I leave the light switch on in the first position or I forget and drive with no brake lights.

The best part is my Bronco is also broke down so I have to borrow a car.

Any one want to buy a Super Awesome Army Truck real cheap?

 

[nf6x]

Is your truck's brake switch a pressure sensor in the hydraulic brake line? If so, its failure may have caused both the loss of braking and the fire. If I recall correctly, there was an MWO to replace the hydraulic brake switch with a pneumatic one because of problems with the hydraulic ones failing and causing complete loss of braking.

 

[two.fiveM35]

Sorry to hear that. Good luck with the fix, keep us updated.

 

[Barrman]

Nofearnohope had the same thing happen to him a few months ago during a parade. Yes, the military moved the brake switch from hydraulic to air actuated. The -20 talks about it some and the Ps magazine cartoons shows you what has to be done too.

 

[gungearz]

That's some really bad luck... Hope to see some pictures of the rebuild job. Good luck...

 

[Heavysteven]

Does not sound like the end of the world. It's Common knowledge that these kinds of issues come up with a 40+ year old trucks. I would do a complete brake inspection from sure from the master blinder to the airpack, brakes lines, and wheel cylinders.

 

[Mike O]

I experienced almost the same thing in my M35A2 except mine was a bad airpack instead of the MC. I'd been driving my truck and noticed the pedal getting closer to the floor. I made a bee-line for home before the brakes died completely. I saw brake fluid spewing from the slobber tube and the air-pack. It was then that I noticed a burning rubber smell. A quick look under the truck revealed a melting hydraulic brake light switch. I rebuilt the air-pack and MC, replaced the brake switch and spliced in a new brake light wiring plug. Haven't had any problems since, but it could have been disastrous.

 

[nf6x]

I recommend making the modification to replace the hydraulic brake switch with the pneumatic one. The hydraulic brake switch is a known safety problem.

 

[mobileauto2000]

I experienced almost the same thing in my M35A2 except mine was a bad airpack instead of the MC. I'd been driving my truck and noticed the pedal getting closer to the floor. I made a bee-line for home before the brakes died completely. I saw brake fluid spewing from the slobber tube and the air-pack. It was then that I noticed a burning rubber smell. A quick look under the truck revealed a melting hydraulic brake light switch. I rebuilt the air-pack and MC, replaced the brake switch and spliced in a new brake light wiring plug. Haven't had any problems since, but it could have been disastrous.

That fire scared me more than anything, I will be using the same kind of switch as I already have one, BUT there will be an inline fuse down there when the wiring is fixed

 

[DeucesWild11]

I did mine after I broke off the hydraulic one by accident. It's really easy. Here is a schematic to help you along.. I think Erik's has the kits.. also the PM article.. Man I am making it really easy for ya..

 

[erixun]

I did mine after I broke off the hydraulic one by accident. It's really easy. Here is a schematic to help you along.. I think Erik's has the kits.. also the PM article.. Man I am making it really easy for ya..

Thank you for "making it easy"!!!

If I am correct, that is what this site is supposed to be about.... helping each other enjoy the hobby. Far too many times instead of giving a helpful answer, I see comments like "read the TM" or "do a search, there are already threads about this." While the TM's are helpful, experience is a far greater teacher, and not all "new guys" have that.


Sorry to hi-jack the thread for a single post, hope the brakes get fixed and don't sell your truck!