The Stovebolt Site Forums The Shop Area Engine Shop Is it wrong to run an engine without a thermostate?

I Googled this and there were dire warnings. But is it damaging to an engine to run without one? It would seem to me it would be more free-flowing and cool the water quicker without one. At this time I am not sure what temp I have in mine. I am trying to anticipate issues for the trip to KC.

Running without a thermostat will NOT “hurt” your engine. It may not be ideal to do so but it won’t hurt. If you are concerned about such problems on a road trip, put a thermostat gasket and a tube of gasket sealer in your tool kit for the trip.

It isn't generally a good idea to do this, Ron. You want the water to remain in the radiator long enough to allow heat to be dissipated into the air and if it runs through freely and too fast, you'll end up running your engine hotter than you might want. Also, in the winter the reverse applies. You want the water to remain in the engine long enough to maintain the proper temperature of your engine. As for a proper thermostat in the 235 it depends on where you live. If you live in a place like Dallas where the daytime temperature in the summer is guaranteed to be at least 100 F, you need a 160 degree thermostat. If you live where the temperature will be cooler...maybe in the range of 90 or 93, you may prefer a 180 degree thermostat. Please remember a thermostat does not determine the maximum temperature your engine will run. It determines the minimum temperature your engine will run and today's thermostats are not as accurate as yesterday's thermostats were.

It supposedly causes wear due to running too cold for too long, fuel wash in the cylinders from the choke, once up to temperature it will make no difference. Some say without one the coolant moves too fast and doesn't have time to absorb or dissipate the heat, but a well made thermostat has a pretty big flow rate, so not sure that holds true. Their purpose is to let the engine heat up quicker because a hot engine is way more efficient than a cold one.

If the radiator isn't up to the task, then it doesn't matter what thermostat you have, it will always over heat if it can't get rid of the heat. Thermostats have little effect on dirty blocks as long as they open.

It has been said by someone smarter than me that the vast majority of engine wear occurs shortly after startup until the engine reaches its designed temperature.
The termostat in the closed position greatly reduces wear to the engine by reducing the amount of time that the engine is below the designed operating temperature.
Running an engine without a thermostat will cause undue wear everytime you start a cold engine. Undue wear is damage.
If your engine runs too hot with a thermostat, you need to determine what is wrong with your cooling system or your engine which it causing it to overheat.

I can tell if an engine has been run without a thermostat when I tear it down for a rebuild. There will be a shiny spot less than an inch wide on all the piston skirts- - - - -the rest of the piston will be covered with varnish where it has not been in contact with the cylinder walls. Those pistons are either worn out, or badly in need of skirt knurling to get the diameter back to normal.
Piston skirts are egg-shaped, with the widest point at right angles to the wrist pins. As they heat up to normal temp they get round because there's a couple of "anti-expansion" struts cast into the piston. That only happens at normal operating termperature.
Jerry

52Carl got it.
The worst wear is starting an engine from dead cold, and the longer it runs at low temperature the greater the wear.
If you're not going to drive it, don't start it at all.

Last winter I installed a Safety-Stat I bought from NAPA. I didn't really want a Safety stat but that was what they had in stock because they not only fail open, they do that the first time the engine temperature exceeds some predetermined temperature that a truck engine regularly exceeds. On a long, hard pull both my 235 and my 261 will hit about 205 and sit there till the top of the hill.

Sure enough by the time I got home from Arizona the engine was taking too long to warm up and getting too cold on the down-hills. I never pegged the temperature gauge (212 version). This is not the first time I've had this happen. Lately, I replaced the Safety Stat with a regular 180 what with fall approaching. It's been over 90 everyday for a few months so I didn't worry about it over the summer.