Dark Fluid in Reservoir

[elerner61]

2007 M with 80K miles. I'm a religious full brake/clutch fluid flusher every two years. I'm due for a flush and noticed for the first time that my fluid is dark. I've never flushed the ABS system, only done standard flushes.

Brakes and clutch feels fine. Thoughts on what might be going on? I no longer have an INPA setup PC, to do an ABS flush. Thinking I'll give it to my mechanic to do a full flush including ABS and then watch the brake fluid. If it goes dark then I've got some master cylinder (or clutch cylinder) seal aging.

Has anyone been through this before? Thanks in advance.

[mmm-five]

Done any hard braking recently...or more hard than usual that could have caused overheating? Is the fluid at the correct height, any sign of leaks?

[elerner61]

No particularly hard braking events that I can recall. Fluid level looks good and I don't see any signs of leaks (though I haven't looked very closely around the master cylinder).

One blip is that around a year+ ago I was experiencing a "hitch" sort of feeling in the clutch movement when the car was cold. It went away quickly once I started driving and things began to warm up. I bought a new clutch slave and master cylinder in preparation to swap those out...then the hitch cleared up after a few months.

Maybe I'll try and get INPA running on a laptop again and do a full (with ABS) flush myself and then monitor the fluid...or have my indy do it.

[The HACK]

A picture might help. You can also use a moisture tester. Some brake fluid change color as moisture is absorbed, maybe there’s a corrosion somewhere along the line that is allowing water to be absorbed into the fluid.

[elerner61]

A moisture test is a good idea. That would confirm whether it was from moisture or as you say some contamination. I don't think a picture is going to help. The car is very clean, doesn't go out really in inclement whether (but still sees around 7K miles a year). Our heated seats are great!

I tapped a contact I know who has been a BMW master tech for 2 decades or so regarding the need to flush the ABS system as a maintenance routine. He basically said "no". Here is his response:

"We dont normally bleed the abs module. The fluid goes from the frt and rear ports on the brake master through the abs module to the individual wheels. So it is getting flushed but there are some parts that won't be flushed as the valves are not being opened and closed unless they are activated thru the tester. You could go out and stomp on the brakes to activate the abs and then do your flush. I wouldn't worry about it. I have always done just regular flushes on all of my BMW's and never had a problem. That's what we do here at work"

[Efthreeoh]

Originally Posted by elerner61

A moisture test is a good idea. That would confirm whether it was from moisture or as you say some contamination. I don't think a picture is going to help. The car is very clean, doesn't go out really in inclement whether (but still sees around 7K miles a year). Our heated seats are great!

I tapped a contact I know who has been a BMW master tech for 2 decades or so regarding the need to flush the ABS system as a maintenance routine. He basically said "no". Here is his response:

"We dont normally bleed the abs module. The fluid goes from the frt and rear ports on the brake master through the abs module to the individual wheels. So it is getting flushed but there are some parts that won't be flushed as the valves are not being opened and closed unless they are activated thru the tester. You could go out and stomp on the brakes to activate the abs and then do your flush. I wouldn't worry about it. I have always done just regular flushes on all of my BMW's and never had a problem. That's what we do here at work"

I've owned BMWs for 30 years and all of them have had ABS from my '89 E30 onward. I've never run an ABS module flush. Just about to go over to the shop now to flush the Z4.

[elerner61]

I happened to catch a live episode of MotorWeek a few days ago while I was eating lunch (never been a fan). Believe it or not "Goss" as in "Goss' Garage" is still at it and during his tech tips he was advising all the Impala owners out there to make sure that when their shop flushes their brake system every two years (he got that right) that they also flush the ABS pump system. Oh boy, so many opinions on this.

[Molez93]

Originally Posted by elerner61

I happened to catch a live episode of MotorWeek a few days ago while I was eating lunch (never been a fan). Believe it or not "Goss" as in "Goss' Garage" is still at it and during his tech tips he was advising all the Impala owners out there to make sure that when their shop flushes their brake system every two years (he got that right) that they also flush the ABS pump system. Oh boy, so many opinions on this.

I caught that episode as well. Goss pretty consistently espouses the manufacturer party line for maintenance. Been doing my own brake fluid flushes on all my vehicles for 20 years, including 13 for the Z4M, and have never had any issues skipping the ABS specific step.

[pwrdbym]

I've done a hundred brake flushes over the years and always skipped the ABS pump. The key is to do the flushes frequently so there's never really old fluid anywhere in the system. You can do a flush and then do another in about a weeks time and that will likely get most of the old fluid out of the complete system. Be sure you're draining (sucking out) the old fluid from the reservoir prior to the bleeding process, this ensures a more complete flush.