Air temp vs breaks?

[Brenda]

Ok I called Craig over at Tank Land to see if he ever heard of this before and he told me to post here.

California air temp during the morning was 48deg, I drove from San Pedro (USS Iowa) to Crono Ca and breaks felt squishy. Break had more movement than any other time I have ever drove it. Truck sat at depot till late date and temp got to 89deg that day, jumped in and breaks felt fine. Now I know it might have been something other than the temp of the air and all that. Logic says that even if water is in the lines it wouldn't change that much right? It would have to be well below freezing to freeze any water in the lines and clearly that can not be it, or am I wrong in this thinking?

What I checked. MC and fill level good, all lines had no leaks and no dimples from being smashed or anything, wheel cylinders also where free from any leaks. Air lines don't hiss any place that I can tell. According to grip sheets found in truck major overhaul was in 1991 and it sat till a few years ago.

Thanks for any help/ideas as this one has me stumped as well as worried (truck red tagged till I find out what is wrong)

 

[dabtl]

What went wrong? Just asking.

 

[glassk]

When a true catastrophic failure of a brake system does occur, it is most commonly associated with some type of brake fade. Brake fade can be broken down into four main categories including: friction fade, mechanical fade, fluid fade, and domino fade. To best understand the causes of each type of brake fade, we will first discuss basic brake theory.


http://www.crashforensics.com/brakefailure.cfm

 

[wreckerman893]

Give your brakes a break.

 

[Brenda]

Ok so the lack of sleep over the past few weeks and major surgery on my mind, my internal spell checker was off. Thank you the word would be brakes.

 

[gimpyrobb]

If you have not taken the hubs apart and inspected your brakes personally, its time to do so. You will be able to inspect the bearings while you are in there too.

 

[Tow4]

Speaking from personal experience I can tell you, a catastrophic brake failure is easily identified by the brake pedal on the floor, a massive fluid leak from a wheel cylinder, master cylinder, brake line, etc. and a seat cushion sucked up your A. If the brakes still work, even poorly, it's not a catastrophic failure.

Brake fade is usually the result of heat. You know the brakes are fading because they become less effective and the pedal does not go to the floor. Brake fade happens after high speed or long down hill braking.

Spongy is going to be air or some contamination that is compressible, or brake line flexing from deterioration, hence the soft pedal feel.

I would do an inspection of the brakes looking for leaks and check all flexible brake lines. I replaced all the flexible lines on my Deuce when I got it just for peace of mind. If you don't find any issues, bleed the system to get any contamination out. If you haven't done it, it might be time to pull the wheels and look at the wheel cylinders. All the wheel cylinders on my Deuce were junk from water contamination. They were so badly pitted they were not rebuildable.

 

[welldigger]

Just because you don't see brake fluid running down the back of a wheel doesn't mean your wheel cylinders aren't leaking. All 4 of my rear wheel cylinders were bad but there wasn't a drop of brake fluid outside of the hubs.

 

[Brenda]

This is what we did, Allen saw that the fluid was not purple and decided it needed to go. We flushed the system and put in new DOT5 made by GUNK in and started the normal bleed process. We have not taken off the wheels yet but when I get out of the hospital we will. But let me tell you with the system flushed out and with the new GUNK in there the truck STOPPED on a dime. Seriously I've never seen one stop like that before. We loaded it for a test and tried it again with same results.

So folks if the fluid is like a golden yellow color it might not be good! Lesson learned without killing myself or anyone in the motor pool!

 

[glassk]

When a true catastrophic failure of a brake system does occur, it is most commonly associated with some type of brake fade. Brake fade can be broken down into four main categories including: friction fade, mechanical fade, fluid fade, and domino fade. To best understand the causes of each type of brake fade, we will first discuss basic brake theory.


http://www.crashforensics.com/brakefailure.cfm

fluid fade

 

[welldigger]

This is what we did, Allen saw that the fluid was not purple and decided it needed to go. We flushed the system and put in new DOT5 made by GUNK in and started the normal bleed process. We have not taken off the wheels yet but when I get out of the hospital we will. But let me tell you with the system flushed out and with the new GUNK in there the truck STOPPED on a dime. Seriously I've never seen one stop like that before. We loaded it for a test and tried it again with same results.

So folks if the fluid is like a golden yellow color it might not be good! Lesson learned without killing myself or anyone in the motor pool!

The purple color fading to yellow is normal. You simply flushed some trapped air out of the system. This does not answer how that air got there in the first place.

 

[Brenda]

I do concur Welldigger. However I do not have the time to track it down right now. I understand REO used the KISS idea for keeping truck going so there has to be something we are missing. Could any water in the line work it's way down to the wheel where it could turn to gas? Just trying to chase down a gremlin here.

 

[welldigger]

It is possible to get water into the brakes. Condensation being the usual cause. However water rusts brake lines, wheel cylinders, and other brake components. Also you would have to severely overheat the brakes to cause the water to boil. Unlike disk brakes the wheel cylinder isn't directly exposed to brake heat. It would take a dragging shoe or extended heavy duty brake use to feasibly boil the brake fluid or water in the fluid.

Water in the brakes is bad but keep in mind the only way to thoroughly remove it is to dissassemble the wheel cylinders since water tends to sit on the lowest point of the brake system. The wheel cylinders in this case. Flushing the system is no guarantee that the water will be removed. This is because both the brake line and bleeder are on the top of the wheel cylinder. The water tends to stay on the bottom.