Brakes and smoke under hood

Today I made a trip of about six miles one way, while returning and while stopped at a light I see wisps of blue smoke coming from under front of truck. At first lot where I could stop, i pulled over and raised the hood, could not see any smoke or smell anything burning. Continued on and stopped at drive in to pick up some food. When I restarted the truck and started to back out, I hit the brake pedal and it went waaaaay down, brakes very soft pedal and not much braking. Drove a mile on to the house, again I see smoke from under front of truck, looked under hood, nothing I could see out of ordinary. Brake fluid full. ?? bg

 

Stuck caliper maybe?

 

I had a stuck brake caliper overheating the rotor. I do not recall the soft pedal though. I replaced both calipers and rubber lines and new pads. Problem has not returned.

 

MarkEagleUSA and jghflys, think you are right. I can see part of the disk through the holes in the wheel. The driver side disk is kinda discolored about half way out from center nad the res of it has considerable rust on it like the pad or caliper is not centered. I can,t explain the soft pedal unless the caliper got hot enough to boil the brake fluid. I had that happen on travel trailer on I-25 in down Denver one time. bg

 

[QUOTE="B.G. Smith, post: 2647171, member: 1107" I can,t explain the soft pedal unless the caliper got hot enough to boil the brake fluid. bg[/QUOTE]

certianly possible...if you have an IR themrormoeter take a short drive and then use it to check and compare rotor temps on each side to see if one is sticking or if they are running normal temps.

 

I just had a similar problem a couple weeks ago. The "smoke" turned out to be atomized brake fluid escaping from a pinhole in one of the two brake lines running from the master cylinder to the ABS thingy beside it. My pedal went to the floor and I had no brakes until I replaced the brake line. Two of the lines go through a bracket and the other two don't. The two lines going through the bracket were both heavily corroded and one was the one leaking, so I replaced them both. Problem solved.

 

I finally bled the front brake and have the good pedal back so that indicates to me that whatever happened did boil the fluid or at least forced some of it out of the pistons. I am still physically unable to work on the brakes but I plan to replace both front calipers and pads.

 

Finally changed the front calipers and pads and all is well. It was the drivers side caliper froze up. Thanks for the replies. bg

 

Just a FYI.... I have done two brake fluid changes on my 2007, 5.9. When I change the fluid, I pull each wheel and pull out the brake pads so I can compress the caliper pistons. I take my, (Looks like a caulking gun) throttle holder that I use for charging AC and put it on the brake pedal and put it against the pedal and push it down enough to close the return port in the master cylinder. This makes it so I can open the bleeder and compress the pistons in the caliper and have the fluid come out of the bleeder and not go back to the master cylinder. I do this a few times to exercise the caliper pistons as well as changing the fluid.

 

In the front you can do that without disassemble anything.

Take a piece of wood, around 9 to 10" long, put it between caliper and axle housing and have someone turn the steering wheel slowly. So you can push back the pistons easily.

I had to do that once on the road when a caliper froze up and i had no tools around.
I cycled the caliper a couple times that way till it was freed and I could continue the trip.

 

Great idea with the throttle holder, I have a collapsible ski pole that I used, put it on pedal and against seat and slide seat forward (just don't go too far and puncture seat) I did bleed what was in the calipers out and some additional while bleeding. Last time I had someone pump the brakes for me to bleed was on a 80s Chevy truck. I told him to press on the brakes and he pushed the master cylinder mount out through the firewall. bg

 

RE: Brake fluid tester
In the latest print TDR issue, 111, an "Editor's note" added to this thread recommends ordering a brake fluid tester from Geno's Garage. I researched these testers, all of them, months ago hoping for help knowing when the water content of my race car brake fluid indicated a need to change it. The result of the research is that their accuracy to the fraction of a percent water content that you need, to make it a good decision tool for changing brake fluid, just is not good enough to be very useful.
The practical consequence is that you could get a "reassuring" tester value (not perfectly dry but not yet bad enough to seem hazardous), and on a long downgrade using your brakes heavily you might still have the brake fluid boil in one or more calipers and produce a soft or "all the way to the floor and no brakes" pedal, because the accuracy of the tester could be off by just enough to make that possible. They will tell you if the fluid is very fresh and dry, or very bad and "long gone", but the middle range where you hope for accuracy is not that precise.
Before investing in one, or trusting one, I recommend you yourself research the subject of their accuracy and decide for yourself if these offer enough accuracy to make them a good investment. I decided not to do so.