Many people have not had problems with the dust shields. Yes, mine had the vents built into them...

I'm just lucky I didn't hit anything when my brakes overheated and went out. It scared me to death! The pedal became mushy and it wouldn't stop.

Everything returned to normal after it sat in a parking lot for a few minutes. It was as if nothing had happened.

That was 7+ years ago. I still have the 400E. All that has been done to the brakes since that day was to remove the dust shields and perform routine maintenance such as periodic fluid change, pads and rotors.

In other words, it wasn't a master cylinder going bad...

I will say that moisture in the brake fluid will make a brake system more suceptable to boiling, and boiling is apparently what happened. My calipers became so hot that the fluid boiled and could not apply pressure.

Was my problem exacerbated by moisture in the fluid? We will never know, but the car was being maintained and periodic flushing of the brake fluid is part of the maintenance process...

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02 S500
92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)