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I can agree to that, ....ummm,... to disagree that is, errr,.. without meaning to be disagreeable you understand. So wer'e all in agreement? Well, I think i'l just go shut my mouth now.

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Could this be a contributing factor in running hot? Why the need to run two fans?

If the thermo is pushing air through the radiator would the air be able to get through the fan spinning on the other side? In most cases when running a thermo, the factory fan is removed in order to provide a number of benefits - increased hp, cooling only when needed, quieter running.

Of all the great suggestions you have received, one is missing. The water pump. Are you getting the proper amount of flow?

Also drilling a hole in the base of a 165 degree thermostat will not hurt, but will not cure an overheating problem.

When you add coolant it should be a 50/50 mix of water and antifreeze.

Good luck

ahhh i'm not getting into this here - i understand where you're coming from Dodgeman, but i think there's more to it than that.

we'll agree to disagree and leave it at that

Oxygen is released when the water is boiling & by this time, the presence of oxygen as a free gas is really accademic. The visible bubbles in boiling water are normally steam, which are created at the point where the heat is high enough. Interestingly enough, the conversion of water to steam absorbes a great deal of heat & is a surprisingly good, if unpractical, method of cooling. The Rolls Royce Goshawk aircraft engine was to be steam cooled, but it was not a practical design.

The amount of pressure in the cylinder block behind a partially opened thermostat is not sufficient to be an issue as the pump is not a positive displacement type & the pressure is usually kept very low by the by-pass that recycles coolant from the head directly back to the water pump, by-passing the radiator. Coolant under pressure does not hold more heat than unpressurised coolant. It just holds higher temperatures before boiling.

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If you'd like I could wander out to the assembly line tomorrow at work and see if the 2005 Tacoma's and Corolla's have thermostats.
I'm pretty sure they do.

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beg your pardon?

i'm not talking about heat TRANSFER here, i'm talking about the ability of the coolant to stay as coolant and cool, like it's supposed to. if the coolant boils, it aerates and loses it's ability to cool.

when coolant boils, it releases oxygen yes? is oxygen in the cooling system now -not- an aerated cooling system?

you said yourself that
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therefore if the thermostat is slowing the coolant flow, holding the coolant back AND PROVIDING PRESSURE (however insignificant), then surely the PRESSURISED coolant will be able to hold more heat...? yes?!

we can all argue what it's intentions are meant in a factory application, but there is only evidence of what it actually does which is what i'm basing my argument on.

Quote:Ummmm....... not quite.
Cars ran unpressurised cooling systems without problems for over half a century & many of these cars are still happily driving around.

The boiling point of water is raised by about 3 degrees F for every 1psi that pressure is raised above standard atmospheric at sea level. With the increase in engine efficiency that came about with the introduction of "super" grade fuels in the 50's it became obvious that operating temperatures from 180 to about 195 degrees F were going to be the norm. This was too close to the boiling point of unpressurised water [212 deg. f] so pressurising the cooling system at even 7psi was enough to raise it to 233 degrees which was a good enough margin. This also stabilised the situation at high altitude where the boiling point would be lowered if unpressurised.

The ability of heat to transfer to the coolant is not significantly [if at all] affected by pressure in the cooling system. The only way to aerate the coolant is to introduce air into the water pump which will mix it into the coolant, particularly at high rotational speeds.

If car makers could save 5 cents on each new car by leaving out the thermostat while still being able to provide satisfactory performance & engine life, then there would not be a factory thermostat in the country.

Spend the few dollars that it takes & buy a new one, & while you are at it, give the whole cooling system a proper reverse flush & get rid of the rubbish in there, particularly in the radiator.

Space the back of the bonnet up 5mm and remove the rubber sealing strip on the firewall. That should be good for 5 degrees.

You might wanna put and aftermaket temp gauge on it, just in case the factory units if up the creek, this happens more than I care to remember. Even temporarily. This will eliminat sender and gauge.

try and get a shroud for the fan so it will perform at its best or fit an electric fan, that way you get the most air pumped 'through' the radiator. If everything is fine, thats the only suggestion I can offer