Brake Fluid tester

I have one from Wurth. Don't know who actually made it but is similar to the one on Amazon. Made in Germany.

Good to show customers and for checking cars I have no prior knowledge of but in reality it tells us what study after study has already told us, brake fluid needs to be changed every or every other year, maybe every 3 in the desert.

 

I figure I change it every year in the desert, not much need for something that looks for moisture. We had a 1% humidity day last year. You cannot even do that in a laboratory without a great deal of effort. Have already seen 3% humidity this year.

 

More water than that in Everclear.

 

Brian- Affirmative, normally about 5%.

 

This might be a really stupid question, but how much does the condition of the fluid in the reservoir reflect the condition of the fluid in the brake lines and calipers? Unless I'm missing something, it doesn't seem like there is much fluid "circulation" going on during braking, so it seems like the reservoir fluid might test very differently than the fluid in the lines.

I've also heard of people doing the "turkey baster" change of fluid in the reservoir as quick partial fluid change without flushing and bleeding, but this too seems like it would not be effective without circulation of fluid.

 

The fluid does circulate but the water and debris is typically more concentrated nearer the calipers.

 

Always cringe when I see a TV mechanic just push the brake pistons back in to the caliper (and all the crud/dirty fluid back upstream) to install new pads without opening the bleed valve(s).

 

How much do you bleed out when changing pads?

 

I have seen the operation of a brake fluid tester by our chief of tech at my local car club. The device requires a probe to be submersed in a sample of brake fluid and use a 12VDC supply to power the tester. My understanding is that the probe is boiling the fluid and displays the temp at which this boiling takes place. The higher the level of water concentration in the brake fluid the lower the boiling point.

Over the years I have provided numerous samples to be tested. The samples taken from the brake fluid reservoir are usually within 1% of the original new fluid boiling point. The samples taken from the caliper vary based on age and use but have seen them boil as low as 250F.

For track use vehicles I always use new fluid rated for 550F and flush 1L through the system. My local Ferrari club requires fluid no older than 4 months. Similarly, my local BMW club requires fluid no older than 6 months. For street use only vehicles I use OEM fluid and flush every year.

On occasion we have seen cars at the track experience brake fade and after further investigation we find that the fluid was not flushed as requested by the vehicle owner or not done by the DIYer, they simply bled the caliper. Sometimes the term "flush" is not clearly understood by the owner and/or service writer or mechanic. Requesting that 1 Liter of fluid be flushed may help achieve the desired result.

 

Whatever gets displaced out by pushing the piston(s) back with the bleed screw open, and then bleed out a few~6 oz with the pedal as part of doing a brake fluid flush (which I'm usually overdue for anyway ).

 

I used to not change every year until 3 years ago and even after 1 year it is noticibly different in color comming out of callipers. I also noticed it was a little darker than the reservoir.
After three years it was dark enough anyone who would have seen it with no mechanical abilities would have changed it.

You wont really get the true sense without looking at new fluid and seeing the difference.

 

I change my client's brake fluid annually as part of the annual service. I use a pressure bleeder and typically push out about a liter of fluid. Don't forget the clutch slave.

 

I read years ago about flushing the system with denatured alcohol? Then new fluid.

 

Brake fluid is so hydroscopic (water loving) that moisture passing by the brake caliper seals will equilibrate with the reservoir within an hour of entry. There does not have to be any circulation for this to happen.

As to how often you should change it: note that cars that go on race tracks have their fluid changes within the week prior to the event; much longer and one risks fluid boiling. So back to passenger cars: how often do you really need your brakes to work--that is about how often you fluid should be changed.

 

If done regularly no special steps need be taken. Outside of cars used on race tracks and cars we intend to keep for a long time and are a collection of very expensive or non available parts none of this is an issue so only a very small segment of owners and service facilities even give it a thought.

Just use the proper fluid and change it annually.

 

That would be awful for seals, no?

 

Possibly and if changed annually I see no reason for it.

 

Never even think about flushing with anything other than brake fluid. Denatured alcohol boils at about 175F. Any residue left behind will act just like water in the system only worse because it boils about 40 degrees earlier.

 

Any alcohol has at least 5% water, too, so not a great idea.

 

Thats funny. No setting for silicone brake fluid.


Because you cant. Water does not go into solution, it sinks and concentrates at the bottom, next to the brake caliper, where it is the hottest and now youR brake fluid is effectively 212 degree boiling point.

 

You do not really believe this? No?
Under best circumstances the main components are assembled over here together with the last housing screws by some part time working housewives. What qualifies stating 'Made in Germany'.

Bestmartin