Yes, sir, I have came across this issue before. 2003 buick lacross 3.8 owner changed thermostat, and lost the good heat from the heater. He put in several different thermostats to no avail. He came to me, and we went to buick to get a factory thermostat. The difference between the aftermarket and factory was the dangling check valve, which was the cure for his issue. He and I learned a good lesson. Never use a thermostat without the check valve. It's not worth the headache. If all you can get is a non check valve thermostat. Then, drill a small air hole in the spot the valve would be.
Yes, sir, I have came across this issue before. 2003 buick lacross 3.8 owner changed thermostat, and lost the good heat from the heater. He put in several different thermostats to no avail. He came to me, and we went to buick to get a factory thermostat. The difference between the aftermarket and factory was the dangling check valve, which was the cure for his issue. He and I learned a good lesson. Never use a thermostat without the check valve. It's not worth the headache. If all you can get is a non check valve thermostat. Then, drill a small air hole in the spot the valve would be.
100%. It’s funny how you never forget the cars that have fought being fixed.