Having the thermostat out is not good. That could be causing your overheating.

As for the fan coming on with the A/C, it should come on any time the compressor is engaged. This may not be the entire time the A/C is switched on unless you live in an extremely hot climate. If the van is overheating it will not allow the compressor to engage.

 

Having the thermostat out is not good. That could be causing your overheating.

Not true, that's an urban myth.

The thinking of his myth is, without thermostat, the coolant will not stay enough time in the radiator for it to be properly cooled. When coolant stays still in the radiator, coolant also stays still in the engine block heating, comprende?

It is the other way around, the thermostat is there to help the engine to reach the proper high temperature faster. When enginevis hot, thrrmostat stays fully open until engine "cools down" to the proper temperature.

As long as people keeps promoting thod myth, it will not go away.

 

With the thermostat out the entire system is being heated and cooled. It will take longer to warm up, but when it finally does the temperature runs away. The thermostat's job is to separate the coolant that's getting hot from the coolant that's being cooled. If the entire system is hot and has full flow, the coolant won't stay in the radiator long enough to do much cooling, but will gain more heat from the engine.

It's not a myth, it's a fact I've seen happen over 100 times. If you only drive short distances or in cold weather it might seem like a myth. Let one idle without a thermostat. Might take an hour to warm up, but fully warm to spewing coolant won't be long behind that.

 

100% incorrect. How can you see it 100 + times? If you know is going to overheat, why you keep doing it?

Some guys never learn! ?

It is a myth!

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The thermostat controls the minimum temperature of the engine. It cannot control the maximum temperature. The only way the thermostat can cause the engine to run too hot is if it is faulty and doesn’t open completely (or at all).

It is commonly, but wrongly, thought that a cooler-running engine is better. It is not! An engine prevented from reaching proper operating temperature because the thermostat is “too cold” (opens at too low a temperature), or missing entirely, wastes fuel, wears faster, and dirties its oil faster. If you are removing the thermostat or running a 160° unit to prevent or fix overheating, you’re just masking the symptom of whatever is wrong with your cooling system. Find it, fix it, and run the correct thermostat.
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Source:

About Chrysler cooling systems: Heat and thermostats

About Chrysler cooling systems: Heat and thermostats by Daniel Stern (part 1 in a series) Why do we have automotive cooling systems? As engines burns gasoline, expanding gases push the piston, driving the crankshaft; but only about one quarter of the chemical energy in the gasoline becomes...

www.allpar.com

 

People bring cars in without thermostats or with ones that are stuck open wondering why they are overheating. I don't take them out.

Simple thermodynamics really. The heat differential between the radiator and coolant will be less than that between the cylinder walls and the engine, once fully warmed up. Sure it takes longer to get there, but your engine is designed to run rich to make it hotter until at normal operating temp, so it will get there eventually. Once that happens, thermal runaway kicks in because the "cool" coolant is just a few degrees cooler than the hot coolant. Fans will slow the process, but won't stop it.

 

People bring cars in without thermostats or with ones that are stuck open wondering why they are overheating. I don't take them out.

Simple thermodynamics really. The heat differential between the radiator and coolant will be less than that between the cylinder walls and the engine, once fully warmed up. Sure it takes longer to get there, but your engine is designed to run rich to make it hotter until at normal operating temp, so it will get there eventually. Once that happens, thermal runaway kicks in because the "cool" coolant is just a few degrees cooler than the hot coolant. Fans will slow the process, but won't stop it.

Tell that to those allpar guys, seems like they need your advice. ?

Having the thermostat out and straight water in the system may not be good as the boiling point is lowered. On the flip side, straight water cools better.

Then, if you add water wetter......