DOT 5 water contamination

[lfhoward]

I recently had my M116A3 trailer inspected (PA requires this every year), and it passed. I then took the trailer on a 600 mile trip the next day, half of which was in a severe rain storm.

Today while walking by the trailer, I noticed the master cylinder appeared “wet” with silicone based DOT 5 brake fluid. Upon closer inspection, I found the rubber grommet under the master cylinder cap was bunched up and deformed. The person who did the state inspection must have taken the cap off to look at the brake fluid level, and put it back on carelessly.

Inside the master cylinder I can see some drops of water that have settled to the bottom, no doubt contamination from the rainstorm I drove through. They appear orange because they are causing rust.

So, my question is: Will this require a complete brake flush and new DOT 5 fluid, or is there not enough water in there to worry about?

Thanks in advance.

 

[NDT]

Suggest you suck out the droplets with a turkey baster and then do a bleed at the wheel cylinders.

 

[gringeltaube]

Yes, it appears to be only a few drops in there... But it all depends how much the brakes have been applied, during/after that rain.
If water got all the way into the wheel cylinders you won't get it out via a common bleeding procedure. (DOT5 has a slightly lower density than water..)
You may have to disassemble the WCs to be safe.

 

[lfhoward]

Thank you NDT and gringeltaube for your quick responses.

It looks like the lowest point on the brake line is below the level of the wheel cylinder, so I agree that if water made it down that far, simply bleeding the brakes may not get it out. I might need a power bleeder, which means a trailer shop, unfortunately. I went 300 miles in the rain so I am pretty sure the drops of water we see in the master cylinder are not all there is in the system.

 

[87cr250r]

If you were able to get your hands on some silicone or PFPE vacuum pump oil they are more dense than water and you could float the water out of the system. They would keep any future water up in the master cylinder where it can be removed.

 

[lfhoward]

I decided to have a shop drain the system and then blow compressed air through the lines to completely clear them out. Then they will add fresh DOT 5. That stuff is expensive but it is better than losing your trailer’s brakes coming down the Appalachians next month.

 

[87cr250r]

You can't clear water out of the system in this method. I would suggest replacing the wheel cylinders.

Hot oil circulation is the only way to get water out of these types of systems without bottom drains.

 

[lfhoward]

You can't clear water out of the system in this method. I would suggest replacing the wheel cylinders.

Hot oil circulation is the only way to get water out of these types of systems without bottom drains.

The technician who did the brake flush was former military and recognized the trailer right away. The ideas above were mine (inexperienced with DOT 5 brake systems), but I am sure the person who worked on it fixed it the right way using his experience and the TM.

 

[87cr250r]

For future reference, if you want to dry something out, put it in your oven at 250 °F. It's not hot enough to damage the rubber or grease in the short term and will evaporate all water.

 

[lfhoward]

For future reference, if you want to dry something out, put it in your oven at 250 °F. It's not hot enough to damage the rubber or grease in the short term and will evaporate all water.

Thanks. I suppose the wheel cylinders could have been dried out this way.

 

[Tow4]

I went thru the same problem with my Deuce. All of the wheel cylinders and metal brake lines were rusted beyond repair from water intrusion. I replaced them and switched to DOT3. DOT3 absorbs water and since the water is suspended in the fluid, you can get it out when you bleed the system.