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Monday, June 24, 2024

Doug's Domain

Doug Vetter, ATP/CFI

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Sunday, September 15, 2019

Brake Fluid Flush

(Image: E46 on two post lift in prep for brake fluid flush)

Following a year on the storage lift I took the E46 down to do some essential and long-overdue maintenance -- a brake fluid flush. I'm ashamed to admit the last time I performed this task was way back in 2012, and at that time I had waited more than the recommended two year timeframe (and obviously more than my recommended interval of one year) to replace the fluid. That flush revealed nasty, orange-colored fluid coming from the rear calipers in particular, which was indicative of rust. Rust, of course, comes from moisture in the fluid, which most often enters through the imperfect caliper piston seal.

After getting the car off the lift I let it warm up for a few minutes and then took it out on my local test loop. Driving the E46 after driving the GTI for the last year provided an opportunity to compare the driving experiences of the two vehicles, and no one would call me clairvoyant for predicting the result -- the E46 inspires confidence and encourages aggressive corner entry and exit while the GTI's numb steering, front wheel drive configuration and poor weight distribution typical of that configuration causes me to constantly question the state of the vehicle and pull back for fear of losing control. About the only thing I missed from the GTI driving experience was the ridiculously quick and crisp shifts of the DSG transmission.

Back at the garage I put the car on the two post lift. For some reason -- and I'm not sure what changed aside from the vehicle's exact position relative to the lift -- I was able to get the arms just low enough to get under the jack pads without the fatter part of the arms conflicting with the rocker panels. This bodes well for future maintenance in my brother's facility but I have not changed my recommendation for the ideal lift for low profile cars -- the Rotary 10000 pound in-ground unit.

I have generally come to despise 18 inch or larger wheels, as they are not suitable for the poorly engineered and maintained roads in the US, not to mention ridiculously heavy as compared to the ideal 17 inch equivalents, and the E46's M135 wheels are no exception. However, the one perk of these wheels, at least when installed on this particular vehicle, is that sufficient clearance exists so the brake caliper bleed screws are accessible from the rear of the wheel, meaning a bleed can technically be performed without removing the wheels.

(Image: Old brake fluid flushed from caliper)

I removed the wheels anyway this time around for two reasons -- one, the bleed screws tend to leak during the bleed despite getting a good seal on the tubing leading to the collection bottle and this can result in damage to the wheel paint if one is careless, and two, I felt it was important to clean the hubs and apply a fresh coat of aluminum anti-seize, as the substance is naturally consumed over time due to the reactivity of the cast iron rotor. Of course, I applied anti-seize in 2012 and once the lug bolts were removed the wheels practically fell off the car -- this being a far cry from my attempts to remove them in 2012 because the factory did not, annoyingly enough, apply anti-seize when the car was built.

Once again I performed the flush according to my standard procedure using a pressure bleeder, frequently topped up the reservoir to avoid pushing air into the ABS controller, and managed to push nearly a full liter of fluid through all the lines, starting with the right rear. As I extracted the bulk of the fluid from the reservoir and then refilled it with new fluid I found the old fluid a deeper gold color. The fluid that came out of the rear calipers was once again tinted orange, indicating the presence of rust, but it wasn't nearly as bad as the first time I did this in 2012. Now that the vehicle is stored in a climate controlled environment with low ambient moisture I'm expecting the next flush to present less evidence of rust.

With the reservoir level filled to just below the "MAX" mark and the wheels reinstalled and torqued to spec I returned the vehicle to the four post lift where I expect it to live until the spring when I expect to do a low-utilization oil service and another coolant flush. Till then...

Mileage: 24280