How often do the thermostats Fail on the 7.3? There are a lot references to using Ford or IH thermostats. I am 50 have never had the thermostat failure on a vehicle. Perhaps I have been lucky.

I recently purchased a N/A 94 and it is running a little on the warm side according to the untrustworthy temp gauge. If the thermostat is a high failure part, I will replace it while along with the cooling system flush, tie rods, and changing all the oily fluids.

 

They fail rarely. That being said good coolant maintenance is a must both for cavitation issues and radiator life. The thermostat is made of the same material as the radiator. They do seem to fail if the engine gets hot for some reason

 

They do go bad occasionally but when they do they tend to stay open or shut. Temp gauge sender's go bad to. I've also heard of guys running 210 temp thermostats in the 7.3?

 

Not 210*F thermostats, 203*F thermostats. I've been running a 203*F thermostat for a few years now without my cooling fan installed, too. The heaviest thing I've pulled so far has been my 24' travel trailer and the "needed" gear for me, my wife, and my two daughters. No overheating issues, but the engine has gotten higher into the "NORMAL" range than I like. I'm reinstalling the cooling fan this summer.

I highly recommend the 203*F thermostat. I've had no issues with it or because of it. The main reason I'm reinstalling the cooling fan is for A/C performance.

 

What is the best replacement temp sender? There is a lot of chatter on how bad the temp gauge is but it would seam the issue is with the sender. The dash gauge is basically a volt meter.

 

The problem is the dash gauge doesn't tell you what the temperature is. It does go through a range from cold to hot, but without markings for specific temperatures, you don't have a clue what its telling you. I've also seen a lot of people notice that the dash gauge doesn't move as much as a regular gauge would.

The reality is that most drivers are clueless about how their vehicle works and haven't the foggiest what temperature (or oil pressure) their engine should be running at. And they definitely wouldn't understand how those two variables should change depending on how long the engine has been running, the outside temp, the engine speed, and load you're carrying/towing. So Ford basically just dumbed it down to a couple idiot gauges. At least the temperature gauge shows some variation, the oil gauge was really dummied down to read mid-gauge for anything above like 7 psi.

If you actually want to know the real temperature for your coolant, get a quality aftermarket gauge and sender.

 

If it's a Chinese one it'll fail often:



If it's Motorcraft or International it'll last a good long while. Stock is 190 or 192 degrees, I forget which at the moment. Do not run a hotter or colder stat, it is designed for a specific temp, to alter that temp will result in inefficient combustion or an overheating engine.

 

The sender in my 94 f150 was low and my 89 ranger was high both fixed with Napa parts, probably not the best parts from more resent experience but these did work.

 

I know it is not all ways convenient to buy Motorcraft parts. But in the case of a thermostat and how big a PITA these are to change and as expensive as these engines are to repair why would you gamble on a no-name / house brand god knows where it was made thermostat. That being said you need to inspect every thermostat before purchase hold it up to light and make sure there is no light to be seen around the center. Testing them to see if they open in a pan of hot water is something I also do. Been burnt a couple of times on thermostats so I do a little extra to try and insure I don't have to do the job more then once.

 

I can't speak for the IDI engines, but depending on year, the Powerstroke motors could have a 190, 192, or 195 thermostat.

I have to disagree with this comment. Again, my experience is with the Powerstroke motor. IH/Navistar originally designed the motor to use the 203*F thermostat. Ford started using the lower temperature thermostat ratings in order to comply with Federal emissions requirements.

I have noticed that with the 203*F thermostat, my engine runs smoother, has better MPG, and lower emissions. The lower emissions is verified by the emissions testing required in Idaho.

 

Huh, I just looked up the Motorcraft T-stat at Rockauto, this is clear as mud:

 

Wait a second there, you are contradicting yourself, if the higher engine temps reduce emissions, (which they do), then Ford wouldn't have switched to a colder T-stat to comply with federal emission requirements.

If you have this information on the IDI being designed for the 200 degree stat please share it here, I honestly would like to see that.

The higher engine temperatures of recent years designed into the modern engine are due to emission standards, but the IDI was released in '83 and the diesel emission requirements were pretty loose then and even most gassers weren't running temps in the 200+ degrees yet.

 

This whole emissions thing is a contradiction low engine temps create CO emissions high temps create oxides of nitrogen emissions. Diesels have always ran better at the high end of the temperature scale.

 

Exactly.
For best fuel economy, we want as little as possible CO emissions(because it means unburnt fuel); NOx emissions don't affect economy.

 

I got 2 cents to toss in here for kicks.

To my thinking we(diesel owners) want a very high temp thermostat, basically the highest we can safely run with pressure/boiling point being the limiting factor. This is even more true on IDI's as we want a very hot precup. High temps, most of all of the precup prevent heat/energy loss and promote complete combustion leading to more efficiency. High coolant temps have been shown to increase the fuel efficiency of most engines most of all diesels and is rather common in the trucking industry.

However we want rather cool oil, oil should always be over 212deg(warmed up of course) to remove water but no higher in order to help with piston cooling.

A diesel should produce very little HC or CO emissions, if it does then your only blowing fuel(smoke) out you tailpipe. But a diesel will produce a lot of NOx emissions due to the very high temperature combustion.

The government regulation of NOx is a big pet peeve of mine. I have found no substantial evidence that NOx emissions damage anything. Sure concentrated they are bad but most forms are very unstable and don't last long outside the tailpipe. The forms that are stable are safe, for example laughing gas. However the regulation of NOx emissions has killed fuel economy and engine development in the US for decades. And now the regulation of NOx emissions in diesels is killing an economy that relies on diesel engines. Almost everything you buy at some point goes by truck, most things multiple trucks. The crazy regulations of OTR truck engines is killing the efficiency of the trucking industry adding huge costs to the cost of transporting everything you buy and passing that cost on to you. For what, it's a global warming tax and you are paying it every time you shop.