We had really heavy rains here today. I was in my '99 M5, idling in traffic when I noticed the brake pedal feel became really notchy. When I let go of the brakes the pedal would not travel back up easily and the engine started sputtering until I gave it a bootful of throttle. I also noticed a lot of steam coming out of the exhaust when adding copious amounts of throttle.
This kind of behavior is well-documented on M5 forums - basically the compartment containing the brake booster fills up with water when the drain plug gets clogged, which has the effect of ingesting water into the engine through the brake booster vacuum line (not to mention the booster itself). If enough water is ingested, it can result in hydrolock.
I'm not concerned that the engine reached the stage of hydrolock while running, mainly because the engine would only idle poorly or stall whenever I pressed the brake pedal, and would idle well after the exhaust blew out a decent amount of steam via 5-10 seconds of high throttle.
What I'm concerned about is whether it is safe to turn the engine over now that it is cold, since steam may have condensed to form water in the combustion chambers.
I should mention that before turning the car off after reaching home, I pulled up the handbrake and gave the car 5-10 seconds' worth of sustained high throttle to blow out the steam, but have no way of telling if that was enough to make it "safe" for the engine.
Is it possible to determine if the cylinders are too flooded to safely turn over?
In the absence of such a test, I was thinking of pulling the spark plugs, siphoning off any water using a vacuum line and cranking the engine over manually.
I'm open to suggestions.