Is your rear heat on? providing good heat?
Likely cause of little / no heat is low coolant level in the radiator, with the level being at or below the level of coolant in the lines going to the heater coil. Less heat going downhill and more heat going up hill will confirm that.
Before changing or replacing anything, I would top the coolant up to the underside of radiator cap and see if that makes a difference.
If you are losing coolant, there could be several things causing leakage including a not tight enough radiator cap (lugs should line up across radiator) or a defective cap. If a leak cannot be located, without pressure testing, a new radiator cap is an inexpensive experiment.
As for the thermostat, check the upper radiator hose to see if it is really hot. Compare with another vehicle if possible. With an open thermostat, your temperature gage will likely be showing a lower heat temperature.
What's the history on your coolant system? Antifreeze type (HOAT?), been flushed recently? coolant replaced recently? stop leak been added at some time?
Last edited by Jeepman; 12-06-2010 at 12:36 PM.
2007 GC SXT - Magnesium - S&G - 3.8L - 154,180 kms
2002 GC Sport - Stone White - 3.3L - 336,400 kms
2003 Jeep TJ Sport - 4.0L - 268,600 kms