Step 1: Gather the required tools and supplies.You will need a 3/8” drive ratchet, a long (12”) 3/8” drive extension,a 3/8” drive 8mm socket (prefer 6 point but 12 point will work), a 3/8” drive torque wrench,a pair of channel-lock pliers,a 19mm wrench,a large drain pan or CLEAN 5 gallon bucket and some rags for cleanup.
Optional,but highly recommended supplies include some penetrating oil,needlenose pliers,and a new hose clamp for the upper radiator hose.

Step 2: Open the hood and allow the engine to cool off. Locate the thermostat and thermostat housing midway down the front of the engine, between the fuel filter housing and the upper alternator.



Step 3: Once the engine has cooled sufficiently to work on, position the bucket/drain pan beneath the petcock in the driver’s-side lower corner of the radiator. The petcock on my 2002 had a white hexagonal knob on the end but differing years may have different color or aftermarket radiator drain mechanisms.



Step 4: Remove the cap on the degas bottle, then open the petcock with the 19mm wrench. The draining coolant may splash a little, but using a 5 gallon bucket will contain the spattering better than a flat pan will.



Step 5: Once the radiator has drained, close the petcock while being careful not to overtighten and break the knob. Squeeze the clamp around the thermostat housing-end of the upper radiator hose with the channel-lock pliers and slide it up the hose approximately 3” or remove it completely.

In case one needs a replacement Radiator Draincock, Napa P/N BK 6051366. DAMHIKT... about $5.




Step 6: Spray some penetrating oil around the head of the three bolts holding down the thermostat housing, then wait a few minutes for the oil to work. After ~ 5 minutes, remove the three bolts using the ratchet, long extension, and 8mm socket. I almost-completely removed the rear-most bolt that way, then removed it with the needlenose pliers so that I wouldn’t drop it. Once the bolts are removed, remove the old thermostat housing, thermostat gasket, and thermostat and dry the area. I chose to throw away the OEM housing, since it was corroded and would most likely have started to leak had I tried to reuse it. Instead of another OEM housing, I purchased a billet aluminum replacement housing from Bob Riley at http://www.dieselsite.com along with a 203-degree thermostat. A replacement OEM housing and 195-degree thermostat will also work well.







Step 7: Place the new thermostat where the old one was, then place the new gasket on top of the thermostat flange.



Step 8: Place the new housing on top of the thermostat and gasket. Make sure that the gasket stays in position around the edge of the thermostat flange and doesn’t get squeezed out of place when you fasten the housing down. Tighten the thermostat housing bolts to 15 lb/ft. Be careful—it is very easy to overtorque or break the bolts and using a torque wrench for this step is very sensible.



Step 9: Using the channel-lock pliers, squeeze the hose clamp open, place the end of the upper radiator hose over the thermostat housing, then position/release the hose clamp on the end of the radiator hose.



Step 10: Pour the coolant you previously drained back into the degas bottle. This may have to be done in several steps, since the coolant has to flow from the degas bottle down into the radiator so be patient.

Step 11: Clean up any spilled coolant, then start the engine and check for leaks.