I was having a long running problem with poor performance under 2000 rpms and I could not figure out which direction to take. I don’t have any diesel shops around that I really trust, and like most of us here, I was trying to save money. Madvan, C00Nhunter, and TJ Beggs helped me determine that I needed to get my engine oil temp up since the PCM uses this to regulate timing for the engine (reps sent).

I put the 203 in last night and my engine oil temp went from 155-168 degrees up to the 200 degree range and my water temp (I installed a water temp gauge) cycles from 205 degrees down to 195 degrees. I don’t really know how accurate the el cheapo temp gauge is. Most importantly, the truck is driving like it should. Instead of a stumbling out of tune rpm rise, I am getting a nice smooth acceleration with some push into the seat.

If you are running an old thermostat, check this link out when you can read it thoroughly.
http://www.dieselsite.com/index.asp?PageAction=VIEWPROD&ProdID=186

For me this is a great modification and I would not want to be without it in the states with colder temps. Thanks to all who helped me get this problem solved.

 

Enjoy the new found MPG and Cab heat.
Have a photo of the old t-stat? Brand?

Bill

 

You can get a plain old Stant 205°F thermostat (short style) at your local parts store.

It fits the 94-95 Ford pumps or the T444E International pump.

 

Yes, I know, but I read this on the Dieselsite (credits to Dieselsite) and my truck is a 97:

Although International still uses a 203o thermostat in some applications and that thermostat is available at most auto parts stores, it is the wrong part for the 1996 - 2003 Powerstroke. DO NOT USE THIS! It has a shorter shaft and will not shut off the internal pump bypass. This will cause inaccurate coolant flow direction through the engine. This IH version thermostat mentioned is available by calling us.

The thermostat in the Powerstroke 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 and it won't be covered under warranty.

We know the warranty departments and engineers at Ford have verified engine loss due to the short stem thermostats in previous cases where people were sticking into their trucks to increase their operating temperatures.

 

You can put either style pump on your engine AFAIK. Just something else to consider if you are already changing the pump, and/or want to upgrade to a coolant filter.

It should be noted that IH only makes a 192°F in the short style (original 203° IH t-stat is superseded by the 192° also)

 

X2 Knotwild!

You even have to watchout on the pump.
I have a pump with the non bolt on inlet pipe.
1 piece casting. It uses the long stat.

Bill

 

Unless someone tells me that IH and/or Ford says that running the 203 will damage my engine or shorten the life of it, I'm sticking with it. The truck runs 10 times better, although I realize that the thermostat that I took out must not have been working. I wish one of you guys had been here to drive it before and after.

 

Yup. Diesels want the heat in them!
The stat's temp was lowered for emission reasons.
The hotter you can run the motor the longer it will last.

Bill

 

My truck was built in 12/95. My engines sticker says 96 model on it. Does that mean I have a long stem stat?

 

Almost certainly a '96. Breakdown the VIN and that will yield the official production year.

 

Trucks are so old now you have to look and see.
You never know what pump is on the motor.

Bill

 

Excellent point.

 

i hooked the ngs up to mine today, only 144 degree oil temp max

 

Joe

That 144* oil is why those punks in the 150 gasser spanked Ya!

Bill

 

Joe: I can't wait to hear what it does in your truck.