2001 DEVILLE HAS NO LEAKS BUT RUNS HOT. WHAT IS THE PROBLEM,WATER PUMP OR THERMOSTAT.

They are known for head gasket problems..get it check

First, you must have a properly installed thermostat that is working correctly. Second, Northstar engines are notorious for air in the cooling system after draining and refilling - keep checking the purge tank level after overheating and after the cooling system cools down. Third, make sure your cooling fans are working correctly (relay, fuse, temperature sensor) - check to make sure both are running when it overheats. If all the above is correct, the problem will probably be blockage in the system (try a flush) or your water pump itself is failing.

what is the temp? is the radiator fan operating? The fan wont come on until approx 225f

as long as the mixture is 50/50 water to coolant then i would say faulty thermostat stuck closed replace........cheap parts have seen 3faulty in a row b4.hope this helps.

2001 Cadillac Deville 4.6L SFI DOHC 8cyl Removal & Installation procedure...

1. Before servicing the vehicle, refer to the Precautions section.
2. Drain the coolant.
3. Remove or disconnect the following:
Negative battery cable
Upper fill panel, if equipped
AIR injection control valve, if equipped
Air cleaner
Oil level indicator tube nut, if necessary
Water pump belt cover
Water pump drive belt
Lower radiator hose
Thermostat bypass hose from the coolant inlet housing
Water pump cover

4. Remove the water pump by rotating it clockwise using special Tool J 38816-1A (water pump remover/installer).

To install:

1. Install the water pump with a new O-ring, by turning it counterclockwise using the special tool, until it stops. Torque the water pump to 73 ft. lbs. (100 Nm).

1. 
   
   

Fig. To ensure proper operation, be sure to install a new O-ring (click for zoom)

2. Install or connect the following:
Water pump cover. Torque the bolts to 89 inch lbs. (10 Nm).
Lower radiator hose
Thermostat bypass hose to the coolant inlet housing
Water pump drive belt
Water pump belt cover
Oil level indicator tube nut, if necessary
Air cleaner
AIR injection control valve, if equipped
Upper fill panel, if equipped
Negative battery cable

3. Refill and bleed the cooling system.
4. Run the engine and check for leaks.


Hope this helps (remember to rate this comments)

flush your radiator first.with the thermostat out you should see the water moving if not bad water pump.this engine needs the thermostat to function properly and either a 50/50 coolant or straight coolant so it does not boil over.also make sure your fans are coming on

First, provided their are no visible coolant leaks and/or loss of coolant with no signs of leaks, I would thoroughly flush cooling system and replace coolant, then check and/or replace thermostat (you can place thermostat in boiling water to check for proper function), if you have tried these 2 steps and still are experiencing overheating you may need to replace your water pump which can be a tricky job if you're unfamiliar and try to do it yourself, however, I could walk you through it if necessary. Also visually check your radiator hoses for bulges, wear ,etc along with heater hoses etc. You may want to also check radiator fins to see if they are dirty/obstructed and clean if necessary. Let me know if I can assist you further and how it works out

Well there could be a couple of problems if you live in a hot place you should change the thermostat to a lower tempatured one so the water will circulate sooner that will help it run cooler if that doesn't do it it might need the radiator flushed.

Check temp control sending unit and thermostat.

pull codes from on board diagnostics turn key on not running press and hold hot button on temp and off at same time till dash lights up write down codes respond with all computer codes i will help you determine prodlem and try to fix