DieselSite 203* Thermostat, Ford (1996-03) 7.3L Power Stroke

203* is the temperature that Navistar designed the 7.3L to run at. This is the thermostat that was and still should be in every 7.3L Power Stroke.

Until 1996, all 7.3L Power Strokes that were manufactured used an International water pump and an International short stem 203* thermostat. In 1996, Ford changed to a lower degree 195* thermostat. They changed water pump designs at this time as well. The new pumps required the new long stem 195* thermostat in place of the short stem to properly seat the bypass disk. All 1996-2003 Ford 7.3L Power Stokes came equipped with a long stem 195* thermostat. Recently the factory replacement thermostat available at the parts counter changed to 192*. The DieselSite 203* uses the correctly sized t-stat with the correct temperature spring so that you no longer have to give up the benefits of running your vehicle where it were meant to run.

Diesels run most efficiently at approximately 200* or above. A factory equipped 192*/195* thermostat will maintain an operating temperature at approximately 165*-170*. The Power Stroke has such an efficient cooling system, that this low flow when the thermostat is slightly open is normally enough to keep the engine cool. The downfall to this is that the engine, when not under load, never begins to reach its optimal operating temperature. The 203* thermostat maintains a minimum operating temperature of 190*. This brings the operating temps up from as low as 170* to as high as 203* depending on the operating conditions of the truck. This is closer to the operating temperature range that is preferable for optimal efficiency.

When your engine is under load and is producing higher combustion temperatures the 203* will allow the engine to run even closer to its optimal operating temperature. If the truck is under load and reaches the 203o setting, the thermostat is then fully open. This means you are at the maximum coolant temperature that the truck will reach. Your maximum temperatures are only a few degrees higher than in stock configuration, but these are degrees that you want for better performance. The best benefits come when the same truck is under a light load and would have a hard time reaching this optimal temperature. As stated above, you will never reach this optimum temperature with the stock 195* thermostat. The end result of installing the 203* thermostat should be slightly better fuel economy, less smoke, and maybe a few extra "ponies" to go along with it.

Although International still uses a 203* thermostat in some applications and that thermostat is available at most auto parts stores, it is the wrong part for the 1996 - 2003 Power Stroke. DO NOT USE THE INTERNATIONAL VERSION! It has a shorter shaft and will not shut off the internal pump bypass. This will cause inaccurate coolant flow direction through the engine. The thermostat in the Power Stroke not only controls operating temperatures, but properly directs the flow of coolant through the engine. As the thermostat opens, it proportionally closes the bypass. With the thermostat fully open, the bypass is mostly closed, and vice versa. With the International (Pre-96 Ford) thermostat, this cannot be controlled properly because of the shorter bypass stem. The shorter stem of the IH (pre-96 Ford) thermostat allows the thermostat to be fully open while the bypass is fully open. This means the coolant can travel in any direction available, whatever direction it chooses. It can either travel through the radiator or simply make the shorter, less restrictive path back through the front of the engine. This will cause uncontrolled overheating in the back cylinders of the block, with absolutely no signs of danger showing on the water temperature gauge in the cab. It is possible that the back of the engine can have no coolant flow at all yet the thermometer in the outlet of the water pump shows all to be normal. Multiple things can happen at this point. Cylinders can seize, freeze plugs can fall out and other normal symptoms of an overheating engine may occur. Worst case is a blown motor.

You reach a higher optimum operating temperature safely, by using the DieselSite 203* thermostat with the long stem for bypass protection. They've combined the two units to bring you a safe alternative. Now you can have the optimal operating temperatures without risking the chance of uncontrolled overheating in the back cylinders of the block due to an uncontrolled bypass.


Warranty Information:
-90 days on manufacturing defects and workmanship only.
-There are no other warranties, written or implied.

Improperly or poorly maintained systems can lead to failures in thermostats. As with all cooling system modifications, a water temperature gauge is a highly important tool in monitoring the system. As with the OEM thermostat requirements, we recommend that you change your thermostat out once per year to insure proper functioning of the unit.