Don't EVER Run Without a T-stat
8950HO said:
I recall reading in a highschool auto shop text book that if an engine is run too cool,170-175 approx*F or,(much)less,that cylinder bore and piston ring wear will increase at a faster rate.
This is very true, and is too often overlooked.
I've read several SAE, peer reviewed, and published papers that show how bore wear will increase as coolant temp decreases.
This rate of gain is exponential. As your coolant temp drops below 180 the bore wear increases very fast. This is part of the reason for cold starts being so hard on motors.
Not even race cars will run without t-stats.
Running without a stat is one of the worse things you can do for the longevity of your motor. Probably worse than not changing the oil often enough, or not using a strong enough mixture of anti-freeze in the coolant.
5-spd GT
I would suspect that the sudden onset of problems is due to a faulty part, other than the stat. Especially since you have replaced the stat, and it did not resolve the issue.
My suggestion; Look for very small pinholes in the coolant hoses. Not only will coolant leak out when the system is hot (and internal pressure is high), but air will leak in as the system cools (which results in a decrease in system pressure). The air then sits in the coolant passages until the next time you start the car. Then, the air will prevent the flow of coolant by blocking the water flow.
I have had this happen to me when I had the stock 302. One of the heater hoses was the culprit.
I realize that many will spout out a bunch of crap on the internet, without knowing what they are talking about. I assure you, I have read several hundred papers at this point, most written by engineers for major auto manufacturers, most of which discussed oil and coolant temps. You do not want to remove the stat all together.
I wish you luck.
jason