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Old 07-12-2008, 10:16 PM   #9 (permalink)
EcoModding Newbie
Join Date: Apr 2008
Location: Southern Ontario
Posts: 284

Parachute - '03 Chevrolet Tracker LX
90 day: 28.55 mpg (US)

Peon - '95 Plymouth Neon Highline baby!
90 day: 31.39 mpg (US)

Slocus Wagon - '06 Ford Focus SE
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Originally Posted by Gregte View Post
My thinking is, if that condition was enough to crack the block or heads then they would already be cracked from normal driving.

The first time the thermostat opens, after you begin your morning commute, the radiator has coolant that is the temperature of the out of doors, perhaps as low as -20F on a December morning. But at some point the T-stat opens (engine finally reaches +195F) and the cold coolant rushes in. But alas the engine survives it, day after day.

For that matter, I expect the radiator coolant probably cools back down to near -20F every time between when the T-stat closes and then again opens, at least on a -20F winter day.
I haven't looked at my cars myself but someone posted recently here that the coolant is pumped through the heater radiator all the time as it by passes the thermostat. Also the thermostat doesn't pop open, it opens gradually and I also doubt it closes completely on most cars so it shouldn't be a huge temp difference.
I agree though that any production car engine shouldn't mind EOC, highly tuned motorcycle engines for example may not like the same treatment but they produce so much more hp per litre.

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