'91 560 SEL, 150K miles. ABS system briefly activates the front circuit at approx 3 mph as the vehicle is stopping on dry, paved streets. Tire size is the same on all four wheels, pads, rotors and calipers are in good condition, brake fluid is clean and the hydraulic system properly pressure bled.

Any ideas as to what the problem may be?

You either have a bad ABS sensor at one of the wheels or the gears need to be ceaned at the wheels where the sensros are located. I don't know of a way to test the sensors, but my dad's 300E use to do that until a mechanic cleaned the teeth at the front wheels. There are 3 sensors I believe, one at each front wheel and one on the rear diff.
Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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Does your ABS light occasionally come on when the car is in drive but stopped, such as at a red light? If so, will it go out if you put it in park and rev-up the engine a bit.

If yes, then could be a bad over-voltage relay, or more likely low voltage at said relay caused by a low charging output from the alternator.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

ABS warning light has not illuminated... and problem occurs when moving in either forward or reverse direction.

Will check wheel speed sensors and advise.

My 1991 300E is doing it too. I thought I was doing something wrong the first couple of times, but it engages as I'm coming to a stop slowly intermittently, and has been for about two weeks. No ABS lights, so I'll have the sensors checked. Exactly what I came here to ask about. Thanks for the help.

Remove sensors and clean,also clean gears on wheels.Also check lower ball joints,if whore out,will give you the same feeling.