Woodchuck23

I have a 1994 Ram 2500 2WD diesel pickup. Truck is totally bone stock with just over 200,000 miles. I went to move it in my driveway and when I went to apply the brakes to stop the brake pedal lost all pressure and went right to the floor. I pumped it several times with no effect on stopping power but a big cloud of smoke came out of the dash area around the steering coluum. I shut off the motor but the smoke continued for a few more seconds before stopping. The brake pedal has no resistance and will go right down to the floor. I have looked at all 4 wheels and under the hood and cannot find any leakage of fluid and the master cylinder is full. I have looked under the dash and cannot find any burnt wires anywhere. The smell of burnt wiring seems to be coming out of the big plastic wire coupling bolted to the inside of the firewall. Does anyone have any ideas of what happened and why?

Silver R/T

Check all of your fuses. Might have to take wheels off and see if there is a leak somewhere. Hydraulic systems don't suddenly fail and lose pressure, there has to be a leak somewhere, check calipers, wheel cylinders.

gorms

I would also suspect something went wrong with the hydroboost (did 94's have vacuum assisted?), I can't see how any electrical mishaps would cause a loss of brake pedal. The hydroboost is however mounted right on the other side of the firewall. Pedal still drops while the motor is off? Any effect on the power steering? I'd try to see exactly where the "smoke" is coming from! Good luck.

PS a master cylinder can go bad all of a sudden, check for any fluid running down the firewall. Could be a small amount of fluid that leaves the system, but instead the plunger just goes past the fluid instead of making pressure, if that makes sense.

SIXSLUG

Crazy.

I was thinkin brake light switch or trailer brake controller maybe shorting and causing the smoke....

But on a vacuum system, like yours, it shouldn't have affected the brakes. All I can recommend is finding out the source of the smoke, and then maybe checking the MC for a contained failure, such as a blown o-ring or other seal that is letting the fluid bypass pressuring up the lines to the wheel cylinders and calipers.

I would also suggest having someone step on the pedal and make sure your front brake lines aren't ballooning.

In my scenario, your master cylinder failed, allowing your brake pedal to bottom out, pinching or shorting wires to your trucks accessories and gauges.....just thinkin out loud here......

Woodchuck23

Thanks for all of your input on this. Yes the pedal goes to the floor with the motor off. Power steering is not affected. No wires near the brake pedal arm to rub thru.
I have taken it to the garage where I have my repair work done. It is only a short distance from me and used the E brake to get it there. I had a new master cylinder installed about a year ago by this garage and then a new brake controller installed a short time later by another place. Both worked fine up to now.
I will post what we find out.

SIXSLUG

Good news.

A wise old mechanic once told me "If something goes wrong, go back to the last thing you messed with"....sage advice.

Would like to hear outcome.

Kurt

torquefan

This is my first thought here too, but as you say there are no aftermarket wires running close to the brake pedal, the only other thing I can come up with is that you stepped on the pedal and a brake line or hose burst, allowing a stream of brake fluid to spray on something hot under the hood or under the vehicle.

Woodchuck23

I got the truck back from the garage yetersday and it turns out that the main brake line going from the master cylinder to the rear brakes blew apart. They put a new one in and all is well.
Now what the big cloud of smoke was from is still a myistery. They removed the lower portion of the dash from under the steering coluum and inspected eveything in sight and could not find anything that looked burnt or was even hot. The smoke came out from around the steering coluum so maybe something shorted out in there but everything works as it should. So I guess that I will just have to drive it and see if it does it again. This is a little scary to me but I do not have any other choice at this time.

infidel

If you feel wary driving with the electrical problem try tilting the steering wheel up and down repeatedly and see what happens.
Very common for wires under the steering column cover to get pulled out of their connectors.

torquefan

And for peace of mind, keep a 1/2 inch wrench handy, in case you have to disconnect the batteries in a hurry.

NJTman

from a simplistic thought process.

If the pedal went to the floor, maybe it crushed or cut a wire that ran below it, and short circuited on the firewall.


I found a bunch of wires below my brake pedal and if I ever pushed it to the floor, they would have either been ripped out, or pinched below. I've since rewired them....