Last night was my first drive in the rain. I noticed that my brake pedal would pulse/vibrate (just slightly) in time with my windshield wipers at auto stop. I definitely noticed this coming from the brake pedal and no where else and only when the engine shut off.

Anybody else have this? I'm assuming it's just a quirk of the auto stop.

Sorry if this has already been discussed, I was too lazy to look through old threads.

Come to think of it, I have noticed a slight shudder of sorts under those conditions. Never pinned it to the brake pedal specifically. But I have a thought explaining the shudder.

The driver side wiper is HUGE. That's a lot of instantaneous torque needed to get it moving from a stop- its realistic to expect to be able to slightly feel Newton's 3rd law in action when everything else around you is still.

As for why the brake pedal, dunno. I'm not certain of the electrical interactions/control over the brakes, particualrly under static (stopped) conditions. My belief was that vacuum maintained hydraulic pressure as long as the brakes were not repeatedly pumped while the engine was off. Is there an electric motor assisting to keep pulling vacuum since our ICE shuts off by design? If so, that's your answer- the wiper draws a lot of momentary current, affecting the vacuum pump's ability to maintain vacuum, which affects brake pressure momentarily.

Sometimes I amaze myself with my ability to BS...

I too just noticed this recently, but hadn't put too much thought (or BS in gonavy's case) into it. It is a relief to know that other people are experiencing it though and its not something wrong with mine.

My EX does it also. Yes I do set at lights with the engine off sometimes. The wiper motor is connected to the firewall,, so is the master cylinder. Its a small fire wall and thems some big wipers. Our Accord does it also. So does my Ranger. Come to think of it Ive never driven a car that you cant feel the wiper motor running at some level.

What's this thing that you call "rain?"


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