You all may be right, but the immediacy of finding I had no cabin heat right after washing the hot engine, when I started up the car before leaving the car wash and letting it idle a few minutes (normally long enough to produce some perceptible cabin heat, but I wouldn't think long enough to warp a head if the belt was slipping, unless I'm wrong), is what made me think this may not have been a coincidence. Since I had no heat within minutes of washing the engine, and the heat came back only when the warped head and the head gaskets were replaced, that's what leads me to think that the warped head was the cause of the loss of heat, and if so, it seems likely to have warped at the car wash, or else I wouldn't have lost cabin heat starting at that moment. Also, I didn't notice any other symptoms typical of a belt slipping so badly that the water pump wasn't moving: no trouble steering the little bit needed to move out of the washing bay, no odd electrical/alternator symptoms, etc.
But if an engine can heat up enough only a few minutes after being started, to warp a head if the belt is slipping and thus the water pump isn't moving sufficiently, then maybe that was it, so I'll give it a 50% chance of being the cause. If so, then the loss of cabin heat for the first few minutes could have been initially caused by the slipping belt, which then caused the overheating that caused the warped head, which then "took over" in causing the continued loss of cabin heat. I've learned in fixing computers for 25 years that interesting chains of events like this can happen, and without enough analysis, can make one assume that there was a single cause for a single problem.
I've driven in the rain many times since then, and I've sometimes popped the hood afterwards to check for rainwater, and I've never found rainwater on the top part of the engine, at the heads.
My Taurus was my Dad's before my Mom gave it to me in 2006, and he took good care of it--he was an aircraft engineer/mechanic in the Air Force from WWII through Vietnam, and ran his own auto repair shop (with his brother) for a while just after WWII. He passed away in 2005, so there was no overlap during which I could ask him to pass along his auto repair knowledge, because the Taurus was my first real car (I'd gotten away without needing a car most of my adult life, with short commutes to work, bicycling, trains, etc.).
Last edited by JohnSawyer; 04-08-2013 at 02:40 AM.