1999 Cadillac SLS Overheating

You should be able to see it once you remove the lower radiator hose and then remove the flange from water pump. Removal and installation instructions are below.

REMOVAL:
Disconnect the negative battery cable.
Drain the coolant.
Remove the air intake duct.
Disconnect the radiator hose
Remove the thermostat housing.
Remove the thermostat.
Clean all sealing surfaces.

Typical thermostat and housing.

INSTALLATION:
Install the thermostat.
Install the thermostat housing using a new gasket.
Install the thermostat housing bolts and tighten as follows:
1999 models: 15 ft. lbs. (20 Nm)
2000-05 models: 89 inch lbs. (10 Nm).
Connect the radiator hose.
Install the air intake duct.
Refill the coolant.
Connect the negative battery cable.
Start the engine and check for leaks.

Sure. Water pump is on the right side of the engine at the top. I believe it's on a separate belt.

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

INSTALLATION:
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).
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
Refill and bleed the cooling system.
Run the engine and check for leaks.

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