Testing an inexpensive brake fluid tester - "ITEQ" - $10.

[denwood]

In my spring service this year, I've gone done the brake fluid science/testing rabbit hole. This "ITEQ" tester was quite inexpensive ($12 CAD - https://www.amazon.ca/gp/product/B076SC377J/?tag=atomicindus04-20 ) and brake tester accuracy has been questioned online a lot. Turns out it works quite well. Just make sure you test 3-4 times and assume the worst result is the accurate one. It looks to be more accurate as water content gets to 2%.

I used some DOT 4 ATE fluid as my baseline, and added water to a 100ml sample in 1ml increments, stirring it for a 30-45 seconds each time. It's interesting to see how the water mixes right in, which is apparently the idea with brake fluid. It isolates water basically from causing corrosion in the system. This hydroscopic nature is part of the design spec.

I tested the existing fluid in our 2003 Honda (maybe 2-3 year old DOT 3) and 2018 LEAF (likely OEM fill, 4 years old) and both came in at under 1% water content with this tester. I'm converting the vehicles over to Bosch 5.1 on this round of fluid flushes. I figure every 2-3 years will ensure the fluid is both "dry" and that the anti-corrosion package stays active. More on that in the next post.

The images are self explanatory, starting with the DOT 4 fluid I had on hand for testing.

 

[MasterSolenoid]

Good info, thanks.

I had the same tester and also questioned its accuracy.
I went no further.

I decided it was best to just change the brake fluid every two years.

 

[ka9mnx]

I had one and liked it until it died. I also used the copper strip tester.

 

[denwood]

@MasterSolenoid, you are 100% correct. I was more curious to see how the older fluid in our vehicle was doing. Our EV has an electronic brake system integrated the master cylinder and is $4K to replace. Nissan advises yearly brake fluid changes, no doubt as the electronic brake system is working all the time to dial in rear brakes, ePedal mode, etc. So even if the water content is low, you'd still want fresh fluid in there to keep the anti-corrosion and lubrication additives active.

@ka9mnx , based on how low the water content was in our other vehicles, and my 2-3 year flush schedule, I likely won't use the tester a lot for my own cars, but I will use it often when helping out friends/neighbours on the hoist

 

[BHopkins]

@ka9mnx , based on how low the water content was in our other vehicles, and my 2-3 year flush schedule, I likely won't use the tester a lot for my own cars, but I will use it often when helping out friends/neighbors on the hoist

Makes perfect sense. I'm pretty disciplined on changing brake fluid on a scheduled basis on my cars. Using a a brake fluid moisture tester always shows the fluid as no to low moisture content, so no purpose in continuing to test on my cars.

But the tester can be a valuable tool in checking brake fluid on friends and family cars, since most people never change brake fluid. The tool will help show others why their brake fluid needs to be replaced.

 

[JimPghPA]

I have a similar pen for checking the water content of brake fluid and I use it and also lend it out to friends. But I also use the test strips to check the copper content of brake fluid and I give my friends the remaining test strips because I figure they will just go bad with time. To thoroughly test your brake fluid you really need to use the test strips to also test the copper content.

 

[JimPghPA]

If you do some research you will find that Bosch brake fluid really is a much better brake fluid. As for using dot 5.1 it is a brake fluid designed for applications where the caliber gets much hotter then a standard vehicle that is normally driven on the road. Such as vehicles that are driven on race tracks. And also as the number increases the brake fluid is more hydroscopic and a DOT 5.1 will pull water out of air better than a DOT 3 or a DOT 4 and therefore may become contaminated with too much water in a shorter time. Therefore DOT 5.1 fluid should be tested for water content more often and if you don't have the ability to test it then just change it more often.

 

[denwood]

@BHopkins , yes, 100%. I tested our other two cars (2-4 year old fluid) and both tested in that 1% or less range. My expectation is that the 5.1 fluid I'm using now will need the 2-3 year cycle due to it's higher affinity for water absorption.

@JimPghPA , I posted a thread on the military testing of DOT 3/4/5.1 to replace their current DOT 5.0 standard. It's not clear whether the BOSCH DOT 5.1 is the "winning" candidate, but I'm using it primarily due to the much lower kinematic viscosity of 870 mm2/s at -40C (when compared to the DOT 3 standard of 1500). Someone looking for a DOT 3 with exceptional low temperature performance should look at "AC Delco DOT 3 Brake and Clutch Fluid" which is DOW 372LB..the DOT 3 LV in the military test.

 

[JimPghPA]

I can't remember where I saw it, maybe on a YouTube about the BOSCH brake fluid, but it said that it can tolerate some water and not have its boiling point temperature lowered anywhere near as much as standard brake fluids normally will, and actually the boiling point temperature will remain high enough to not cause steam bubbles when other fluids with the same percent of water contamination would fail.

 

[Bailes1992]

If you do some research you will find that Bosch brake fluid really is a much better brake fluid. As for using dot 5.1 it is a brake fluid designed for applications where the caliber gets much hotter then a standard vehicle that is normally driven on the road. Such as vehicles that are driven on race tracks. And also as the number increases the brake fluid is more hydroscopic and a DOT 5.1 will pull water out of air better than a DOT 3 or a DOT 4 and therefore may become contaminated with too much water in a shorter time. Therefore DOT 5.1 fluid should be tested for water content more often and if you don't have the ability to test it then just change it more often.

Not true. DOT 5.1 was actually designed for cars with ABS and ESP to operate effectively at very low temperatures. That's why most racing brake fluids are DOT 4.

 

[ordinarybloke]

Now we're dim enough to buy utter shonk and test it, this in the stead of new fluid and a calendar.

Jeeez... I don't know who comes out the more stupid. Me for reading this, or him for doing it? I think we need to get out more.

Next week's post: Is rear-view mirror grease still sold in quart tubs or do they make us buy the whole gallon?

 

[denwood]

Jeeez... I don't know who comes out the more stupid. Me for reading this, or him for doing it? I think we need to get out more.

Based on that gem, I'm going with option 1, "you for reading this"

I, and others here in this thread, have already noted that a tester is not necessary if you're already doing a flush every 2 years.

On another forum I post at (where folks are more polite) one of the guys purchased the tester and checked two of his older cars. Both car's fluid tested over 5%. He's in Florida, so a lot warmer and humid than most places year round. In that case, testing the fluid reminds us that climate has a lot to do with the change interval. In the Arctic, maybe 10 years is fine. In a tropical climate, ya, maybe two years is too much. Here's Bob's post, which also is a good example of why you don't want to use DOT 5...check the Vette caliper (with rust) pic:

Bob Heine's Auto Emporium

I like Liane's choice of lighting. And she seems to have chosen an adequate installer! Seriously though they do look nice. I may have to check those out for our own place.

www.garagejournal.com

 

[edyvw]

Guys: hygroscopic NOT hydroscopic!

 

[edyvw]

I can't remember where I saw it, maybe on a YouTube about the BOSCH brake fluid, but it said that it can tolerate some water and not have its boiling point temperature lowered anywhere near as much as standard brake fluids normally will, and actually the boiling point temperature will remain high enough to not cause steam bubbles when other fluids with the same percent of water contamination would fail.

It is one size fits all fluid. Made by ATE for Bosch.

 

[denwood]

Guys: hygroscopic NOT hydroscopic!

Noted...my edit window has expired on my posts, but if there's a mod here, have at 'er

"The terms hygroscopic and hydroscopic may sound similar but their meanings completely differ from one another. Hygroscopic substance refers to the substance that can take and hold moisture from the surroundings. Hydroscope is an instrument used to see objects deep underwater."

I've also been guilty of calling brake fluid hydrophillic, which is also apparently incorrect...although brake fluid absorbs water quite nicely (as well as humidty) as shown by my test method.

 

[denwood]

Not true. DOT 5.1 was actually designed for cars with ABS and ESP to operate effectively at very low temperatures. That's why most racing brake fluids are DOT 4.

That 372LB DOW fluid (AC Delco DOT 3 Brake and Clutch Fluid) outperformed all of the DOT 5.1 fluids at low temps which makes it a good choice if you want to stay on DOT 3, but live in a cold climate and want to get the best performance from ABS and ESP. Most EVs (maybe all) will have an electronic brake controller which is actuating brake circuits much more frequently than either ABS or ESP. This adds another element to the conversation as lubricity will play into the long term life of this very expensive component. That DOT 3 had the lowest numbers on the wear tests...

 

[edyvw]

Noted...my edit window has expired on my posts, but if there's a mod here, have at 'er

"The terms hygroscopic and hydroscopic may sound similar but their meanings completely differ from one another. Hygroscopic substance refers to the substance that can take and hold moisture from the surroundings. Hydroscope is an instrument used to see objects deep underwater."

I've also been guilty of calling brake fluid hydrophillic, which is also apparently incorrect...although brake fluid absorbs water quite nicely (as well as humidty) as shown by my test method.

There is hydrophobic brake fluid, Castrol SRF which goes for like $70 for the bottle. Very popular on the track/racing, but very dangerous if not thoroughly flushed.

 

[denwood]

There was a time that I thought brake fluid's (mainstream, not racing) hygroscopic nature was a liability, not realising that this was part of the design spec to prevent internal system corrosion. If you're using products like the SRF, you definitely need to be well aware of the limitations that go with the performance. I was surprised on how quickly the added water (in post #1) mixed in and "disappeared" into the DOT 4 fluid.

 

[JimPghPA]

Makes perfect sense. I'm pretty disciplined on changing brake fluid on a scheduled basis on my cars. Using a a brake fluid moisture tester always shows the fluid as no to low moisture content, so no purpose in continuing to test on my cars.

But the tester can be a valuable tool in checking brake fluid on friends and family cars, since most people never change brake fluid. The tool will help show others why their brake fluid needs to be replaced.

I lent my brake fluid water percent testing pen and also the strips to test copper level and antifreeze PH and freeze point to friends and family members. One friend said the brake fluid in his wife's car failed, and he would have it flushed by his mechanic when it gets inspected. I did not ask him if it failed because of water percent or copper content. He is a retired medical lab chemist and college chemistry teacher. So, I am sure he tested it properly.

 

[JimPghPA]

Now we're dim enough to buy utter shonk and test it, this in the stead of new fluid and a calendar.

Jeeez... I don't know who comes out the more stupid. Me for reading this, or him for doing it? I think we need to get out more.

Next week's post: Is rear-view mirror grease still sold in quart tubs or do they make us buy the whole gallon?

LOL!!!!!