OT - But Metal Content - Overheating Vehicles Q?

I believe you're on the correct end here. The thermostat blocks water movement until the block heats up enough to open it. If it's open all the time or missing, it'll take a loooong time heating up to operating temperature, if it ever does. I well remember a 1000 mile trip in 6 degree weather with a busted thermostat, almost as cold inside the car as outside and had ice on the radiator. Two coats and insulated boots got me through. One of those deals where it was 60s until the night before I took off. CO weather will do that in the winter.

Stan

Short answer: you're right, your friend is mistaken. Operating with no thermostat, the engine can't possibly get any hotter than it does with the thermostat in place and wide-open.

Some engines without the restriction of a thermostat will pass water through the radiator too quickly to shed the heat efficiently, so will gradually heat up. The way to do it is to gut a thermostat, leaving a big washer with a restricter hole in the center where the thermopill used to be..

Right. Racing my old MG without a thermostat made it overheat in a hurry. To improve the water flow, you needed a shaped filler that replaced the thermostat.

Some engines don't do this. But many of them do. Those fillers were commonly available for sports cars that were popular for racing, back in the '60s and '70s.

Is it possible that, without restriction, G forces were causing portions of your engine to lack coolant? Maybe causing steam pockets?

Second thought, aerodynamics requiring radiator top to be below top of engine cooling passages causing uncovering of passages w/o some back pressure from thermostat restriction.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

It was explained in the old tuning manuals as a case of the water flow becoming very turbulent as it flowed into the too-large open space where the thermostat is supposed to be, and restricting flow because of the resultant drag. Personally, I haven't a clue. d8-)

your engine to

Nothing to do with g forces or aerodynamics. The cooling system is still pressurized, and force circulated (has a water pump) Lack of restriction from a thermostat can allow water to move very quickly through some parts of the engine, while not circulating at all through other parts (stagnating - not "air bubbles" - resulting in hot spots from both lack of flow and lack of heat transfer Once a hot spot develops and local boiling occurs, the overheating escaltes very quickly because the steam DOES keep coolant out of the area, causing it to heat up more, causing more local boiling, etc. When pressure in the system due to localized boiling builds beyond cap pressure, coolant is blown out of the system - making the problem even worse.

Some engines really don't care if a thermostat is installed or not. Some without a thermostat will virtually never reach proper operating temperature, and some will overheat VERY quickly without.

What's that Lassie? You say that Joe AutoDrill fell down the old rec.crafts.metalworking mine and will die if we don't mount a rescue by Fri, 23 Oct 2009 15:40:18 -0400:

Some (one that I know of) thermostats act as a Y valve, blocking flow in one passage, and allowing flow in another. Pump moves full volume all the time, but the thermostat changes the ratio that goes to the radiator or the bypass passage.

This is absolutely correct, for a large number of engines. The pump circulates water around the block a lot more than through the radiator. If the thermostat is removed, in some designs it could cause the flow to the far end of the block, for instance, to be much lass than it should be. I'll bet this is what is going on in the ones that overheat without a thermostat.

Jon

Joe, I am afraid this is a very often repeated wife's tail. Running without thermal control will cause oil sludge to form inside the engine, because the water caused by condensation will not get warm enough to boil off and leave the engine as vapor. This water will combine with the residual sulpher in the lube oil creating sulpheric acid. The acid corrodes the oil creating sludge. Steve

cause it to overheat... I believe it can cause it to

But I can't see how it can cause an overheat

a stock system other than the missing thermostat.