Brake Fluid and Testing It

This is true on the motorcycle side. The there is a valve in the automotive caps, but there is air exchange due to fluctuations in ambient pressures. It is not completely sealed. Otherwise, brake fluid would never be able to absorb moisture if it was truly a sealed system.

 

As a certified Harley Davidson, BMW, and Suzuki tech, I was hoping that you would say this...

And you are still false.

I can go out to any one of the 7 motorcycles in the garage and take a picture and show you if you like...

 

This method is an important first step but the system needs to be flushed because water is heavier than the brake fluid. So it sinks to the lowest points of the system, the calipers and wheel cylinders. This causes corrosion in these parts and overtime cause them to seize. This is why a flush is best. The turkey baster just makes sure you have clean fluid when flushing.

 

I was hoping that you would say that you're a "certified tech."

The bellows is currently retracted from a fresh flush.

 

Here is how the diaphragm gasket is when fluid level is at or near full…


And if everything is working properly, here is how the diaphragm gasket is when the fluid level has dropped…


Probably why you cannot see through your brake reservoir in your picture.

 

No shit. I do my own work.

That's nothing like the cap on the automotive side, as I said.

 

Two older Toyotas both with in 300K never had the fluid changed 160k on the latest never touched.

 

Once again, incorrect.

And it is clear that you do your own work.

 

Hygroscopic.

I got it wrong for many decades, too.

Moisture, aka water, is heavier than brake fluid and will go the bottom of the system over time.
In the mid 1990s I was working for a VW & Audi dealership and had a 1988 Audi 5000CS TQ come in with really odd brake problems. Fluid had never been changed, DOT3 back then, and it gelled up. All new hard lines, hoses, master, calipers got replaced.

 

FFS. That is not our Taco. 1970s tech.

Take a seat.

 

I have on older cars (with the reservoir top removeable) drained and cleaned the whole reservoir and in a short amount of time the new fluid becomes dark so, there is some cycling. I always try to bleed especially, the back brakes when rotating tires.

 

This was the answer I was looking for. Thank you! Kinda wasn't sure if water "spread out" through the system, meaning a turkey baster change would remove "some" water. But it seems the effects of a turkey baster change only would be minimal. I'll do it nice and proper when I get a moment.

I should add that a tester, even if accurate, probably won't detect the appropriate water concentration since you can only test from the reservoir.