Testing Coolant and Brake Fluid

I'm at 28k mi and 4.5 years of ownership. It was a COVID buy and she has lived a pretty easy life so far.

In the past, I have flushed my brake fluid on prior vehicles every 2-3 years just as a good practice. This go-round, decided to pick up test strips that do both coolant mix %/ph and brake fluid copper content. Used BK

$22 8006B Phoenix Systems 8006-B Double-Ended Brake Fluid + Coolant Test Strips (15 foil wrapped test strips), 1 Pack

8006B from Phoenix Systems.

Surprisingly, brake fluid came out pristine and coolant was 50/50 and top end of corrosion protection (all expected from the long life pink coolant). Attaching pictures of the three test strip colors.

Wanted to see who else has used these (maybe in a shop setting) and what's their accuracy? Should I also test for moisture content with one of those pen b-fluid testers? Plan is to retest the brake fluid in 6mo but my guess is it'll still be fine.

 

Car Care Nut says you need to test the moisture content of the brake fluid, but the test strips he linked to are the ones you used. https://youtu.be/Imafmy3Ycew

I worry more about the fluid in the caliper. Moisture could seep in past the piston seals. I've seen it come out dark yellow when bleeding the brakes when the rest of the fluid in the system is fine. Not sure if that's due to moisture or if its cooked from heat?

It's probably best just to change it regularly.

 

Not sure if I would wait to have a measurable corrosion level in my brake lines. Rather test for the moisture in the brake fluid which eventually leads to corrosion. Also, the brake system is not one that has a pump and the fluid gets circulated. It is more or less stagnating in the lines. That means that your test results in the reservoir may be significantly different from that at the brake caliper where the heat is produced and changes the brake fluid moisture content.
As the manufacturer recommends, I would go back to the good old habit and change the brake fluid every 2 years.

 

Just like transmission fluid, the manual doesn't actually have a replace timeframe. All it mentions is "inspect brake fluid level/condition". Agree testing gives you an indication of already existing corrosion and I may pull some fluid from one of the calipers. I was still surprised that 4.5 year-old fluid is not higher in copper content. Brake fluid is still in great shape and I'll continue monitoring during oil changes.

 

This brake fluid discussion has been on TW already. Most (if not all) brake fluid manufacturers recommend changing the brake fluid after 2 years. In this case, it looks like a duck but may not be a duck. Looks of the fluid, feel of the fluid, and testers are vague indicators. The cost of the brake fluid is minimal. Changing it every 2 years gives peace of mind.

 

X2

Testing fluid in the reservoir, assuming that's what the OP did, isn't really indicative of what's down where it matters most.

 

It was since it's the easiest point of access. I'll pull some from one of the calipers and report back.

 

Update: tested fluid from the passenger-rear drum and it's between 30-100ppm so fluid still in good shape. I'll retest at next oil change or just end up changing it then. So if your truck is a pavement-pricess and you don't put a ton of miles, chances are your brake fluid is in a pretty good condition even after 4+ years.