Re: Thermostat vs. No Thermostat
Re: Thermostat vs. No Thermostat -- Charlie	Post Reply	Top of thread	Maverick Message Board

Posted by: Ken Merring 01/07/2002, 22:33:57

This is kind of a controversial topic, but why not open a can of worms I used to be of the opinion (and I've heard it many times) that running without a thermostat causes a car to run hot because the coolant moves too quickly through the radiator to be properly cooled. This theory is backed up by evidence that I've seen many cars at work overheat without thermostats and run cooler with them. Hell, I've probably given that advice on this board. I've taken Thermodynamics I & II and Fluid Dynamics here at Auburn now, and from what I was learning, it seemed impossible, so I asked my instructor about the theory. He agrees that it cannot be true. Here's why: Fluids all act alike, and the faster the fluid moves the more heat transfers. Think of it as wind chill. This is why a water pump with more volume cools better, not worse (which would seem to be the case with the old theory) But it is a proven fact that on some cars, the lack of a thermostat causes overheat. Why? Theory: The overheating stems from the fact that removal of the thermostat reduces the coolant pressure in the block (the pressure in the block is determined by the thermostat, the pressure in the cooling system outside of the block is determined by the radiator cap) and makes the coolant more prone to boiling because it is at a lower pressure, causing excessive "steam pockets" of air around the cylinders and combustion chambers. This aeration makes for poor heat transfer to the coolant. ........................ Hello Charlie, I fully agree with the science of cooling as you stated. I feel that other problems incidental to cars are the cause of most problems. The mfg. designs there systems around these principles and its later in the life of the car that problems start to take over. Hardware blockage, poor thermostat opreation, loose fan belts, pressure cap problems, engine in poor state of tune and yes modifacations that increase the cooling load beyond design limits. Coolant is another area. Antifreeze/water mix is for at least three purposes, to increase the boiling point with the help of the rad. cap pressure rating, for freeze protection and for system lubrication. This mix doesnot cool better than straight water (by specific gravity)of the liquids. Water= 1. Using a coolant mix along with a high pressure cap allows the mfg to reduce the radiation tranfer area of the radiator (read smaller)to get cooling into a smaller front area for styling reasons and to save money too. I'm sure I bored many by now so someone else give their take on the subject.

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