Modify the Thermostat

The Ford 2.3L engine likes to run hot for best gas mileage and performance. The stock thermostat is rated at 192 degF and I found that it took the engine forever to warm up. I had resorted to blocking off half of the radiator with cardboard so that the engine would run at around 200 degF. Without the cardboard, it would take 30 minutes for the engine to move from the C mark on my temperature gauge of "C NORMAL H". Then it would hover around just below the N mark. The rating for the thermostats is for when they are fully open. The standard 192 degF thermostat is rated to be fully open between 192 and 198 degF. The thermostat partially opens about 20 deg before it's rating which is around 172 degF. My radiator has sufficient capacity that even with the thermostat partially open, it'll cool the engine dramatically!

Unfortunately, they don't make a higher temperature thermostat for the 2.3l engine so I had to make my own (I'm getting extreme now). I purchased a 205 degF general purpose thermostat to use the high temperature wax plug. What? A wax plug? They use special formulated combinations of wax inside a copper plug inside the middle of the thermostat's spring. The spring keeps the thermostat seal closed. As the water temperature increases, the wax inside the copper plug expands and forces open the seal previously held closed by the spring. Pretty simple design. The nice part is that most every seal and copper plug has the same dimensions

List of 205 degF thermostats that may work (unverified - you need to visually check!):

  • Motorad 383-205 Thermostat
  • MOTORAD 457-205 Thermostats
  • Stant 14252 205f Thermostat
  • Gates 33180 205 Degree Thermostat

Note: Visually check and compare the 205 degF thermostat before purchasing it. I just received an email that showed that not all thermostat wax plugs are the same - the position of the rubber seal may be different.

Here's a 205 degF thermostat taken apart

The 2.3l thermostat is unique in that it sits in the thermostat housing and not the block. It requires two bent tongs to hold it in place. Notice that there are no tongs in the 205 degF thermostat

To take apart a thermostat, you must grind down the tabs flush, then use a punch and it'll pop apart. I've circled where the tabs come through. There is just a little pressure on the spring - nothing to get worried about

Once I had both the 2.3l thermostat and the new 205 degF thermostat apart. I used the 205 degF copper plug and seal with the 2.3l spring and shell to create a new 205 degF 2.3l thermostat. I had to use the 2.3l spring as it's tapered.

You can easily hold the pieces together with your fingers - there's not much spring pressure. I had to spot weld the frame back together in two places. The original tabs are used to line up everything. I put the thermostat in a vice to hold it while spot welding. Than ground down the welds.

Here's the completed new 205 degF 2.3l thermostat ready for installation! Took about 30 minutes to do and that was a first try. I installed the thermostat with a new gasket and took it for a test ride through the city. It warmed up extremely fast (within minutes but I'll find out later when I start it up on a cold morning) and went to the R on "C - NORMAL -H". The interesting part was that you could determine when it openned and closed by watching the temperature gauge. It would very slowly rise to R than open and slowly cool down to N than close. The engine would heat up again to R and the cycle would start over. This is without a fan running as the electric fan is set to come on at L on the gauge.

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Copyright March 2011 Eugene Blanchard