Rick's Free Auto Repair Advice

Lower temperature thermostat

Should I install a Lower temperature thermostat

No!!! In the good old days of carburetors shade tree mechanics would try to fix an overheated engine by either removing the thermostat or replacing it with a Lower temperature thermostat. It wasn’t a good idea then. It’s an even worse idea now.

At best the low stat/no stat switch-a-roo was a temporary fix to a hot running engine. The engine ran ok because the choke would shut off at its normal range and the air/fuel mixture would lean out. The engine wouldn’t run rich because the choke was out of the picture and the amount of fuel was metered based on airflow through the carb. It was inefficient however because the atomized fuel had a harder time vaporizing in a colder engine.

The poor vaporization problem is still an issue in today’s computer controlled vehicles. But the problem gets worse. Today’s computer controlled fuel injection determines air/fuel mixture based on outside air temp AND engine coolant temp. If the computer sees lower than normal engine temps, it adds fuel on the theory that the engine hasn’t “warmed up” yet. All that extra fuel has a harder time vaporizing against a cold cylinder head and the extra unburned fuel goes down into the cat converter. Loading the converter with extra fuel causes it to run at a higher temp which can actually melt the precious metals inside the cat. Since the cat is made in a honeycomb design, the melted metals obstruct exhaust flow and make the engine even less efficient. (New cat=$800)

Bottom line: It’s far cheaper to fix the underlying overheating problem than it is to run rich all the time. Put in the factory rated temperature T-stat because all the air fuel calibrations are based on it.

 

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat



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