98 Ram van, 3.9, Auto trans, 2wd. Over 200,000, Excellent vehicle. Has been well cared for. However, it refuses to run at full operating temperature. 3 different thermastats and nothing changes. All 3 have been 195, but engine does not run that hot. When ideling runs even cooler. Suggestions anyone?

 

How do you know it's not running up around 195 degrees?

 

The air emitting from the blower is only warm, assuming the temp gauge is accurate, the needle will go to the 195 mark for about 5 seconds then drops back to about 165-170. It will not return to the 195 reading. And I used a thermometer to verify temp.

 

That's normal. Heater specs call for output air temperature (on high speed) to be within 40 degrees of the engine temperature. So the air temperature could be as low as 155 degrees before you would start looking for a problem.

Now as far as the engine getting up to full operating temperature, using one of those laser thermometers aimed at the t-stat housing is the best way to verify engine temperature. If you're using a touch thermometer then touch it to the t-stat housing but you'll have to shield it so as to block the air blowing from the radiator fan, if you want an accurate reading.

 

Thanks for the response alloro, but if a thermostat is working properly, the engine temp should remain constant at all RPM or vehicle speeds. The factory Stat was the same way as the replacements. Replacements were Borg-Warner. I find it hard to believe all 3 were bad. The engine does run hotter in the summer but if I idle for just a few minutes the needle falls back to a much cooler reading. Has anyone heard of a TSB about Borg-Warner Thermostats. The current one was installed in 2003. I've learned to live with it, but there has to be a logical explanation for this.

 

You really need to get an accurate engine temperature to know what's going on under the hood. From your description the radiator could be on it's last leg. The lower temperature reading could be the correct one and the higher reading could be due to an overheating condition. We're really just guessing here without knowing the actual engine temperature.

 

What is the temperature of the air coming out of the dash vents? On my van it runs between 137 (idle) 151 (65/70 mph on the hwy).

 

OK, I've worked as an Powertrain engine cooling and HVAC automotive engineer for the past 15 years. One question here has not been asked. Are you using a pre-mixed 50/50 long-life coolant in your cooling system??? If so, flush it and resort back the basic concentrated green stuff 50% and 50% distilled water (or RO water). Never use the long life coolants in Ram Trucks or Vans. The stuff doesn't have the right balance for the temps needed nor the amount of corrosion inhibitors for the cooling loop.

You can also get the temps up a little better with a small pizza box top in front of the passenger side of the radiator behind the grill.

The more water in your cooling system, the better it will keep temps lower and rebound faster to keep cool. However, that's not great in the winter or freezing environments.

 

I've always used the standard green coolant. Radiator and pump are 16 months old and were new, not rebuilt. There is no bubble in the system. I do use a cover over the entire radiator during temps below freezing and that does elevate it some but it still does not run at optimum temp. My neighbor has a chrysler van with the same anomaly. Bottom line tho is this , if the thermastat if operating correctly, it should maintain a constant engine temp of the setting it was designed for, in this case 195. None of the 3 stats that have been in this engine would not do that. BTW, this is a Canadian vehicle. One more thing. If I use the highest blower speed setting it will actually cool the engine down. I can actually watch the needle fall back to a lower setting.

 

Still too cool running the entire with the radiator face area blocked off huh. That is something. Alright, drain 1-gallon of coolant out of the system and replace it with straight green (no pre-mix) coolant. This should raise the temperature some when the engine is warmed up. This would put your mixture to a near 60/40 balance with the 40 being the water.