Opost that may help you:
http://www.trustmymechanic.com/forum...st=0&sk=t&sd=a
If your thermostat is stuck open it is a possibility, because the fluid is not allowed to warm suffiently to warm up the heater core. Or you have major air pockets in your system and it needs bled out.
Try the above suggestions in that post and double check to make sure your fluid level is still topped up, their is no air in the system, and see if your heater hoses are hot or not when the engine is fully warmed up.
Does your overflow bottle seem to have excess coolant go into it? Then you may need to replace your radiator cap.
If your problems occured at the same time and the temp gauge seems to build up slower and stay cooler than it used to, a good bet is probably replacing the thermostat with a new OEM one.
Hope this helps!
Let us know what happens!
- Dale in Idaho