After 70,000 miles I decided it is time to change the radiator, hoses, water pump and thermostat on my 90 E-150 with a 5.0L with AOD. The replacement thermostat, a Robertshaw is rated at 195, wthe original Ford thermostat was a 192. The van does seem to run hotter since doing all this work. Will I gain much by changing back to an original Ford thermostat - does a 195 vs a 192 make THAT much difference. Also, any thoughts on a 180 after market thermostat? It would seem to me that when running down the road pulling my tariler, the thermostat would be basically open wide, regardless of the temperature rating. Incidentally, the radiator I removed and replaced was a 3 row brass radiator. The trailer is about 4500 lbs. I hate to experiment too much as changing a thermostat on this 5.0 is a PAIN in this van.

Thanks for any advice,
Mark

 

I'm no expert but I have replaced all my thermostats over the past 30+ years so I have some reasonable amature experience. A 3 degree difference in T-Stat ratings is in the noise level(barely over 1%) and would not be noticable all other things being equal. The impression that the engine is a bit hooter may come from air in the system, a different coolant mix, differences in the radiator(you mentioned you changed it) or it can be imagination, or it might really be a tiny bit hotter.

When the temperature gets to operating level, especially in summer or under load, the T'stat should be wide open and the water will probably be 10 degrees or more higher than the rating.

The only difference might come from a T'stat that has smaller openings than stock or perhaps the one you have is defective. I have had 2 T'stats fail when brand new over the years. The symptom is that the car runs a bit hotter under normal conditions and a lot hotter under load.

I wouldn't bother with the difference between 192 and 195 unless you felt the new one was defective.

As far as 180 degree T'stats go. Once again at operating temp it shouldn't make a big difference since either one would be wide open and well past the rated temperature. If you do short trips and the engine never really gets to operating temp, or if you live where it is cold, then having a lower temp will make a difference in that the engine won't get up to operating level for some time. I once used a 160 in an engine requiring 180. Worked fine in warm So Cal, but nearly froze my butt off in the snow.

If the engine doesn't reach operating temp, you can get sludge deposits, run rich, cause problems with the Catalytic($$$) converter etc. So use what the factory recommends.

Good Luck,

Jim Henderson