Philes’ Forum – Summer 2017

by NJ BMW CCA

By Vic Lucariello, Sr.

Hello bimmerphiles! In this sojourn into the Philes’ Forum chronicles, I have a follow up to my last column together with a new item on brake fluid.

Last time out, in the Spring 2017 Bulletin, I wrote about using Dexron III-type automatic-transmission fluid [ATF] vs Pentosin CHF 11.S fluid in your Bimmer’s power steering. [You should be able to download the Spring 2017 Bulletin from the NJ Chapter Website.] I advised that, if your Bimmer uses Dexron fluid, you should not change the system over to CH 11.S or mix the fluids. Since I wrote that, additional information has been forthcoming.

After reading the Spring 2017 Philes’, bimmerphile Sal Puleio, inveterate owner of Rennsport Motor Works in Hackensack, contacted me and sent a copy of a BMW service information bulletin, or SIB. [In the auto-repair industry, these bulletins are generically known as TSBs, but BMW has their own name for them.] The SIB in question does corroborate what I had previously written [and what was confirmed by Matt Kimple at Bridgewater BMW], “The mixing of CHF and……ATF is NOT permitted [emphasis mine]”.

However, the SIB goes on to state that if a power-steering system is to be converted from Dexron III to Pentosin CH 11.S, “….the system must be drained as completely as possible.”

Sal and I discussed this, and we concur in recommending that if a power-steering system is to receive a fluid conversion, simply draining the system “completely” is not the best way to go. We recommend that the system be drained [hoses disconnected] then filled with the new fluid [Ah…hoses reconnected], then the vehicle started and warmed up, with the steering moved from lock-tolock [fully right, then fully left] a number of times. Then drain the system again and refill with the new fluid after changing the fluid reservoir.

Why would you want to change your steering-fluid type? Glad you asked. In specific cases, such as certain E46s [3- Series in production from 1998 – 2006] with powersteering noise under certain operating conditions, it may be beneficial to convert from the original Dexron III to Pentosin CH 11.S. According to several sources, CH 11.S has about half the viscosity [measured at 40-degrees C (about 104F)] of Dexron III. Viscosity can be roughly defined as resistance to flow. However, converting an old system to a less-viscous fluid may foment leakage, so be advised of this as well. If you effect such a conversion, the new reservoir will probably already be marked indicating that CH 11.S should be used. If it is not marked, be sure to source or make a label for it.

Much thanks to Sal for taking the time to look up and send me the SIB and for consulting with me on this topic. Rennsport is located on Berlews Court in Hackensack [201- 489-5577]. Sal has been taking care of NJ-Chaptermember Bimmers since 1981, and he has professionalautomobile- technician experience preceding that. Legend has it that Sal advised Henry Ford on the type of transmission to use in the Model T [or was that Henry Ford II and the Edsel?], but that, folks, was before my time.

While we are on the subject of fluids, here is an update on my continued testing of brake-fluid boiling points. In commissioning my new shop here in CO, I finally unearthed the Chapter’s brake-fluid tester.

For those who do not remember my previous articles on the subject, the DOT 3 and DOT 4 brake fluids found in most vehicles today [including the DOT 4 low-viscosity fluid in recent Bimmers] are hygroscopic, meaning that they have an affinity for moisture. Atmospheric moisture gains access to the brake fluid via the master-cylinder-cap vent, the seals on the caliper pistons, and, some say, via osmosis through the brake hoses. The effect of this moisture is twofold: it foments corrosion of the brakesystem components and it reduces the boiling point of the brake fluid. Since brakes get hot in operation, if this heat causes the brake fluid to boil, partial or complete loss of braking will occur. BMW and some other manufacturers recommend periodic replacement of brake fluid, while some other manufacturers inexplicably do not.

It has been my conclusion, particularly after observing vehicles being driven by driving-illiterate folks negotiate the approximately 8-mile descent of Wolf Creek Pass [they drag their brakes almost continuously as opposed to using them as briefly as possible and then letting them cool between applications] that it is pretty hard to boil your brake fluid on the street, even if you try like these folks are doing. [Of course it is a different story on the track.]

An example of this hit [too] close to home when my daughter visited last month. [Thankfully, she does know how to use her brakes properly.] While she was here, I renewed the front-disc-brake pads in her ’01 Jeep Cherokee, and in doing so took brake-fluid samples from both front calipers. The boiling point of this unknown-age fluid tested at only 370 F! Typical parts-store DOT 3 brake fluid tests at maybe 500 F out of the can, while premium DOT 4 fluids like Ate Type 200 test at around 570 F. Some of the boutique [read: expensive] fluids purport boiling points of 600 F or more, but that is fodder for a future Philes’ Forum. The Cherokee has negotiated Wolf Creek Pass a number of times with this brake fluid [see Photo #1], so my conclusion seems justified. After checking Amy’s brake fluid, I asked her how her brakes had felt coming through Wolf Creek Pass. She said they were fine.

That’s all for now, bimmerphiles. See you next time. Anyone wishing to contribute to Philes’ Forum can contact me at vic.sr@njbmwcca.org. I’m interested in tech tips, repair /maintenance questions, repair horror stories, emissions-inspection sagas, product evaluations, etc.

© 2017; V.M. Lucariello, P.E.