Modify the Thermostat Housing

As mentioned before, the Ford 2.3L engine likes to run hot for best gas mileage and performance. The stock thermostat is an odd ball thermostat. From what I can tell is that Ford screwed up with the thermostat housing and attached the heater hose to the housing and not to the block. The heater hose connection is supposed to be located between the block and the thermostat housing with the thermostat inbetween. Instead they put the heater hose connection after the thermostat - in the wrong order!

Rather than fix it properly, they created an odd ball thermostat that poorly compensates for the wrong location of the heater hose. They added two pitiful mounting tangs to offset the thermostat farther into the thermostat housing so that it would seal past the heater hose connection. The thermostat is a pain in the butt to seat properly because of the tangs. It is a very Mickey Mouse solution!

Pain in the butt stock thermostat

Also, the mounting tangs make it difficult for the thermostat gasket to seal against the block. And because there are only two tangs, the thermostat can rock back and forth during installation and not seat the seal properly allowing coolant to leak past. Did I mention that it is a BAD half assed design!

Custom made thermostat spacer

My solution is to build a one inch aluminum spacer between the block and the housing. The spacer will be drilled and tapped for a heater hose fitting. The heater hose connection on the housing will be blocked (plugged). This means that any standard thermostat can be used without modifications. I found that a 198 degF thermostat worked most excellent.

Stock 2.3l thermostat on left, generic thermostat on right


Aluminum is very easy to work with. I started with a 2 1/2" to 3" wide by 1" thick bar of aluminum that I picked up from the local metal supplier. All I did was take a thermostat gasket along to see what scrap piece of aluminum 1" thick would fit.

I used a thermostat gasket as a template. Centered better than the picture to reduce the amount of cutting!

I rough cut the aluminum with my die grinder, then used my bench grinder to get the final shape. The pictures look a lot smoother than it actually is but who cares?

Fortunately, I have a lathe and used it to open the center hole up

I drilled and tapped for a 3/4 NPT heater hose fitting

Here's what you need: Aluminum bar, two gaskets, two longer bolts, heater hose fitting, plug for old heater hose fitting, hose clamp and one 198 degF generic thermostat (not shown)

Here it is installed!

It is a very tight fit and I did have to grind down a tab on the alternator mount to make it fit. That was a big PAIN to do. I had to remove the timing chain cover to install the spacer. The spacer sits flush against the block and the new generic thermostat sits where it is supposed to in the thermostat housing. I don't have a picture but there is a groove in the thermostat housing for the thermostat to sit in.

I use two gaskets: one for the block side and one for the thermostat housing side. I like to use gasket glue on both sides of the gaskets to hold them in place. I had to run the heater hose up and inbetween the two ignition coil packs because of the location of the heater hose fitting. There is lots of room between the water pump pulley so that's not an issue.

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Copyright March 2011 Eugene Blanchard