I appologize for the stupid question but I didn't have time to really look at it on the side of the road. My sons truck over heated I verified it was the thermostat but then just had time to take a quick look before towing him home and haveing to get back to work. Do You have to pull the timing cover and pullys to replace the t-stat? It looks like its buried behind them. It is a 91 ranger with a 4 banger. In advance thank you for your help

 

Drain the cooling system so that the coolant level is below the thermostat.
Disconnect the heater return hose at thermostat housing located on the left front lower side of the engine.
Remove the thermostat housing retaining bolts. Pull the elbow away from the cylinder head or manifold sufficiently to provide access to the thermostat. Remove the thermostat and gasket.
NOTE: Check the thermostat before installing it.



Clean the coolant outlet housing and cylinder head and water pump gasket surfaces. Coat a new gasket with Perfect Seal Sealing Compound B5A-19554-A or equivalent. Position the gasket on the cylinder head opening.
Install the thermostat with the bridge section in the outlet casting. Turn the thermostat clockwise to lock it in position on the flats cast into the outlet elbow.
NOTE: To prevent incorrect installation of the thermostat, the water outlet casting contains a locking recess into which the thermostat is turned and locked. It is imperative that the correct thermostat installation alignment be made to provide coolant flow to heater.



Visually check for full width of heater outlet tube opening to be visible within the thermostat port in assembly. This port alignment at assembly is required to provide maximum coolant flow to the heater.
Position the thermostat housing against the cylinder head. Install and tighten the thermostat housing retaining bolts to 17-20 Nm (12-15 ft lb) .
Connect the heater hose to thermostat housing.
Fill the cooling system with the recommended Premium Cooling System Fluid E2FZ-19549-AA or equivalent and water mixture.
NOTE: A coolant mixture of 50 percent coolant concentrate and 50 percent water is recommended to maintain best overall performance. To avoid damaging the radiator, the coolant concentrate should not exceed 60 percent.



Check for leaks and proper coolant level after the engine has reached operating temperatures.

 

shorter answer... no.