High water % in brake fluid resivoir. Thoughts?

[Molez93]

Fair point. It is a cheap one like you linked. Technically, it’s two of them from different manufacturers because I happen to own a spare. For what it’s worth, a fresh bottle of the same fluid reads 0%.

[RickyBobby]

https://www.bendix.com.au/bendix-new...-fluid-testing

"Bendix does not recommend using a conductivity tester as they have been known to fail when testing freshly opened brake fluid. Conductivity testers estimate the moisture content by converting the conductivity into an estimated boiling point. Since brake fluids vary from formula to formula, this test is not an accurate result unless the tester is calibrated to the manufacturer’s product when new.

Bendix recommends a tester that heats the brake fluid to determine the correct boiling point. Using a boiling point tester is the only accurate way to test brake fluid performance."

Since you do not know what brake fluid your conductivity testers were calibrated to there is no way of knowing if the results you are getting are accurate.

[Molez93]

Originally Posted by RickyBobby

https://www.bendix.com.au/bendix-new...-fluid-testing

"Bendix does not recommend using a conductivity tester as they have been known to fail when testing freshly opened brake fluid. Conductivity testers estimate the moisture content by converting the conductivity into an estimated boiling point. Since brake fluids vary from formula to formula, this test is not an accurate result unless the tester is calibrated to the manufacturer’s product when new.

Bendix recommends a tester that heats the brake fluid to determine the correct boiling point. Using a boiling point tester is the only accurate way to test brake fluid performance."

Since you do not know what brake fluid your conductivity testers were calibrated to there is no way of knowing if the results you are getting are accurate.

OK. I'm convinced my cheap-o tester(s) are likely worse than simply assessing based on known age, appearance, and brake performance. Ive had enough strange results over the years: better off simply not using them.

I just sprung for a real boiling point measurement tool. On the off chance folks are curious what a real measurement produces, I'll update once I have better data in a week or so.

Thanks everyone!

[FR-S2GT86]

One thing I would like to point out here is that your ABS system may also need to be flushed in order to remove all of the fluid in the system. A simple bleeding of the system at each wheel will NOT flush whatever is inside the ABS module. For that, you need to have a diagnostic tool that is two-way and able to turn on and off each of the individual solenoids inside the module.

And since it’s a BMW, there is probably a lengthy procedure to accomplish this. You will probably never get all of the old fluid out if you don’t go through this procedure which may result in there still being moisture in the system when you go to test for it.

[Ernest72]

Originally Posted by FR-S2GT86

One thing I would like to point out here is that your ABS system may also need to be flushed in order to remove all of the fluid in the system. A simple bleeding of the system at each wheel will NOT flush whatever is inside the ABS module. For that, you need to have a diagnostic tool that is two-way and able to turn on and off each of the individual solenoids inside the module.

And since it’s a BMW, there is probably a lengthy procedure to accomplish this. You will probably never get all of the old fluid out if you don’t go through this procedure which may result in there still being moisture in the system when you go to test for it.

I agree but after 17 years on my WRX, I have had no issues with just bleeding the corners to get the fluid out of the caliper. ABS still works, check it every winter in the snow.

[FR-S2GT86]

Originally Posted by Ernest72

I agree but after 17 years on my WRX, I have had no issues with just bleeding the corners to get the fluid out of the caliper. ABS still works, check it every winter in the snow.

We’re talking two different vehicle manufacturers here. BMW are NOTORIOUS for making things difficult for the home mechanic. I’d be willing to bet that their ABS system is completely different in design and requires completely different maintenance procedures from that of a 17 year-old Subaru WRX.

Somehow the OP got moisture in his fluid at some point. That fluid is pumped through the system by the ABS pump inside the module.

Think of it like draining your automatic transmission fluid. You’ll get most of the old, dirty fluid out of the pan, but you still have all of that old, dirty fluid in your torque converter left when you’re done. Unless you’ve completely flushed the fluid out using the proper procedure, the remaining fluid trapped in the torque converter will eventually mix with the new fluid that you’ve added to the tranny to compensate for what you drained out of it.

Here’s a story: When I helped my son change his transmission fluid in his Scion tC, instead of dropping the pan and just draining it out, we pumped it out using the transmission cooler high pressure line up by the radiator just by idling his engine and shifting the tranny in and out of all the forward gears and reverse gear. Once the flow slowed down enough to let us know it was empty, (and without running the pump completely dry) we would shut off the engine then pump new fluid back in on the return hose using a drill-operated fluid pump until it showed on the dipstick.

We repeated this procedure several times until the color of the fluid coming out of the high pressure hose looked like the new fluid that we were pumping into it. It took several hours and about four gallons as we were doing this in our garage at home and we were using makeshift tools. It was very messy, and I would hate to have to do it again, but at least we walked away knowing that the job was done properly.

I then had him take his car to a local shop the next day to install a new pan filter kit that he had purchased and top it off using the exact same fluid we used that they drained out during that process.

So basically, we performed the difficult and messy part that none of the local shops around here would do. And yes, we called several different shops and none of them would perform a complete tranny flush like we did.

My point for bringing up this story is that had we not performed a complete flush of his transmission, the nasty burned fluid that was left over in there had we just let a shop perform a standard “transmission service” would have just mixed with the couple of quarts of new fluid. Short of pulling the entire transmission, completely disassembling it, physically cleaning it all out, reassembling and reinstalling it, this was the next best thing we could have done.

Older cars with brake systems that don’t have ABS are simple and flushing the system is as easy as bleeding the lines at all four corners topping the master cylinder off as you go until the fluid is nice and clean. But cars nowadays just AREN’T that simple. You just won’t get all of the brake fluid out unless you follow the correct procedure.

[Ernest72]

Originally Posted by FR-S2GT86

We’re talking two different vehicle manufacturers here. BMW are NOTORIOUS for making things difficult for the home mechanic. I’d be willing to bet that their ABS system is completely different in design and requires completely different maintenance procedures from that of a 17 year-old Subaru WRX.

Somehow the OP got moisture in his fluid at some point. That fluid is pumped through the system by the ABS pump inside the module.

Think of it like draining your automatic transmission fluid. You’ll get most of the old, dirty fluid out of the pan, but you still have all of that old, dirty fluid in your torque converter left when you’re done. Unless you’ve completely flushed the fluid out using the proper procedure, the remaining fluid trapped in the torque converter will eventually mix with the new fluid that you’ve added to the tranny to compensate for what you drained out of it.

Here’s a story: When I helped my son change his transmission fluid in his Scion tC, instead of dropping the pan and just draining it out, we pumped it out using the transmission cooler high pressure line up by the radiator just by idling his engine and shifting the tranny in and out of all the forward gears and reverse gear. Once the flow slowed down enough to let us know it was empty, (and without running the pump completely dry) we would shut off the engine then pump new fluid back in on the return hose using a drill-operated fluid pump until it showed on the dipstick.

We repeated this procedure several times until the color of the fluid coming out of the high pressure hose looked like the new fluid that we were pumping into it. It took several hours and about four gallons as we were doing this in our garage at home and we were using makeshift tools. It was very messy, and I would hate to have to do it again, but at least we walked away knowing that the job was done properly.

I then had him take his car to a local shop the next day to install a new pan filter kit that he had purchased and top it off using the exact same fluid we used that they drained out during that process.

So basically, we performed the difficult and messy part that none of the local shops around here would do. And yes, we called several different shops and none of them would perform a complete tranny flush like we did.

My point for bringing up this story is that had we not performed a complete flush of his transmission, the nasty burned fluid that was left over in there had we just let a shop perform a standard “transmission service” would have just mixed with the couple of quarts of new fluid. Short of pulling the entire transmission, completely disassembling it, physically cleaning it all out, reassembling and reinstalling it, this was the next best thing we could have done.

Older cars with brake systems that don’t have ABS are simple and flushing the system is as easy as bleeding the lines at all four corners topping the master cylinder off as you go until the fluid is nice and clean. But cars nowadays just AREN’T that simple. You just won’t get all of the brake fluid out unless you follow the correct procedure.

Yeah I am not disagreeing with you. But I imagine a large percentage of BMW owners never do this and the brakes work just fine. That said, enthusiasts like us want things working their best, so I could see myself or others trying to do it correctly.

[FR-S2GT86]

Originally Posted by Ernest72

Yeah I am not disagreeing with you. But I imagine a large percentage of BMW owners never do this and the brakes work just fine. That said, enthusiasts like us want things working their best, so I could see myself or others trying to do it correctly.

Agreed. However, the OP’s original problem wasn’t that his brakes weren’t working properly, it was a complaint of moisture in his fluid which would come back after bleeding them. That’s what I was attempting to address and offer a solution to his particular problem.

[Molez93]

Originally Posted by Molez93

OK. I'm convinced my cheap-o tester(s) are likely worse than simply assessing based on known age, appearance, and brake performance. Ive had enough strange results over the years: better off simply not using them.

I just sprung for a real boiling point measurement tool. On the off chance folks are curious what a real measurement produces, I'll update once I have better data in a week or so.

Thanks everyone!

With the Farcom DF.16 tester, I got a boiling point of 182 C.
Fresh fluid which is essentially the same, reads 250 C.
The plan remains the same: bleed and replace the cap. Check again in 6 months.

[RickyBobby]

If you are using Pentosin Super DOT 4 brake fluid it has, per specs, a BP of 265°C and a wet BP of 165°C. If your brake fluid is reading a BP of 182°C, then yeah time to change it. http://www.pentosin.net/specsheets/P...SuperDot_4.pdf
Never heard of a Farcom DF.16 tester. Misspelled, should be Facom. You spent some bucks, even used not cheap. https://www.ebay.com/itm/FACOM-DOT-T...75.c100623.m-1