Thermostat Myth

[Bob Ayers]

I had to replace my radiator last Monday, due to a "drip" coming from the core to tank seal. The system was clean, but I always do a distilled water FLUSH (about 10 gallons) running the engine without a thermostat to get the most flow through the system, before replacing the thermostat. It was in the mid 90's, so I thought I would prove (or disprove) the myth about an engine overheating without a thermostat. I drove it about an hour at highway speeds, and stop and go city traffic, and the temp gauge never got above the bar on C. (red circle in the photo below. This photo is a previous photo of the instrument panel):

The myth was disproved, no overheating without a thermostat!

 

[kevinsranger]

i think it varies car to car, depending on the efficiency of the cooling system! i ran no thermostat in my mustang for quite a while, and never over heated, but i doubt a honda civic or something like that would be as understanding

 

[mentalbreakdown00]

Yes it depends on the cooling system, if it's a high flow low temp drop like most vehicles are now probably won't hurt a lot other than a cel and or never going into closed loop. Now some of the odd systems that use very low flow, but big temp drops will overheat.

 

[LearjetMinako]

Removing the thremostat usually prevents overheating by allowing free flowing coolant through the system. But in winter time, it sucks not having enough heat coming out of the vents. My mom's Blazer thremostat was seals were gone. It would stay around 160*F all summer (100*F heat) and stay just above the first mark in the winter. New thermostat later, it now hoovers around 190*F in the summer and above 160*F in the winter.

 

[RustedRanger]

I have never heard that one. But I do know if the outside temp is cold the vehicle will take longer to warm up and run too cool.

 

[strvger]

used to run without thermostats on a somewhat regular basis many, many years ago when i was growing up. wasn't quite as cold there as where i'm living now, but overheating those old cars and trucks was never an issue without the thermostat.

 

[85_Ranger4x4]

i think it varies car to car, depending on the efficiency of the cooling system! i ran no thermostat in my mustang for quite a while, and never over heated, but i doubt a honda civic or something like that would be as understanding

+1

Also notice it never got up to operating temp... which isn't good for your engine.

Not everything needs a thermostat. Heck, my old John Deere B doesn't even need a water pump... from the factory. It just has a way bigger radiator than it would otherwise need.

 

[kevinsranger]

+1

Also notice it never got up to operating temp... which isn't good for your engine.

Not everything needs a thermostat. Heck, my old John Deere B doesn't even need a water pump... from the factory. It just has a way bigger radiator than it would otherwise need.

i wanted my engine at the lowest temp possible, it was a carb'ed 351, and i wanted it to run rich

 

[gw33gp]

There is one thing you are not considering. The thermostat also helps to balance flow and allows coolant to flow evenly as possible to all parts of the block. If you don't want to run a thermostat, you can run a blanking sleeve that replaces the thermostat. They are use in a lot of race engines.

When you run without a thermostat or blanking sleeve, you may see that the coolant is not over heating as indicated by the temperature gage. However, you can get hot spots in some places in the block due to non uniform coolant flow. Your temperature gage will not tell you about the hot spots, it only gives you average temperature of the coolant. Some engines are worse than others but I would never run any engine, that was designed to with a thermostat, without a thermostat or blanking sleeve.

 

[Bob Ayers]

There is one thing you are not considering. The thermostat also helps to balance flow and allows coolant to flow evenly as possible to all parts of the block. If you don't want to run a thermostat, you can run a blanking sleeve that replaces the thermostat. They are use in a lot of race engines.

When you run without a thermostat or blanking sleeve, you may see that the coolant is not over heating as indicated by the temperature gage. However, you can get hot spots in some places in the block due to non uniform coolant flow. Your temperature gage will not tell you about the hot spots, it only gives you average temperature of the coolant. Some engines are worse than others but I would never run any engine, that was designed to with a thermostat, without a thermostat or blanking sleeve.

I agree, I'm not suggesting running without a thermostat at all. There is some theories that if the coolant circulates too fast through the radiator, it doesn't have time to transfer heat, and the engine will overheat. I didn't see this with the experiment on my little Ranger. One other possibility is the water pump cavitating easier without the
thermostat, but I would probably have to run the engine continuously at 5000 RPMs or higher to see it. But this would cause no flow into the radiator, instead of too fast of a flow.

 

[robertc1024]

I had an old BMW 2002 that was close to overheating. Pulled the thingy that the t-stat was supposed to be in (it was in-line with the radiator hoses) and there wasn't one. Put the correct t-stat in, no more overheating. That always made me believe and preach the rumor. I'm glad you did your test though, that's very interesting.

 

[mentalbreakdown00]

I agree, I'm not suggesting running without a thermostat at all. There is some theories that if the coolant circulates too fast through the radiator, it doesn't have time to transfer heat, and the engine will overheat. I didn't see this with the experiment on my little Ranger. One other possibility is the water pump cavitating easier without the
thermostat, but I would probably have to run the engine continuously at 5000 RPMs or higher to see it. But this would cause no flow into the radiator, instead of too fast of a flow.

You didn't read my post, some vehicles, have a low flow, high temp drop cooling system, where the flow system only lets a little bit at a time by, but drops the temp of the coolant signifigantly, this is not common in cars, but it has been tried. If you take the thermostat out of this it will over heat, there are a few trains that run this type of setup.

 

[Bob Ayers]

You didn't read my post, some vehicles, have a low flow, high temp drop cooling system, where the flow system only lets a little bit at a time by, but drops the temp of the coolant signifigantly, this is not common in cars, but it has been tried. If you take the thermostat out of this it will over heat, there are a few trains that run this type of setup.

We are talking automobiles (cars and trucks) not trains. So, there is no point is discussing low flow, high temp drop cooling systems.

 

[mentalbreakdown00]

Not to split hairs, but there were some vehicles this was tried on. Was early on in the car era, I think 30- 40's but can't think of a specific one off my head. But the thermostat regulates flow, and will cause localized hot spots, also another thing if you never get your oil up to temp it will not flow correctly either, which if you have no t-stat the oil will never get warm enough.

 

[tbirdsps]

Gee I wish I could get my temp gage to read that high in the winter. That way I could get heat. In the summer I have no problem getting heat in the engine.