Anecdotal evidence is worthless. Just because that worked on that truck doesn't mean its that way for all of them.

The cooling system is just that, as system. The thermostat is the component of the system that regulates the temperature. It does that by two methods, opening and closing at predeterminded temperatures and rates, and by regulating flow. The radiator is designed to dissapate heat at a particular rate. If you pump the water through it too fast it doesn't have time to cool before it leaves the radiator.

Most racing cars do not use a thermostat. Thermostats are not required for fast warmup and a failure would cause a DNF (Did Not Finish) and ruin an otherwise perfectly good (and expensive) racing engine. However, the rate of flow still must be regulated so most racing engines have a flow restrictor placed in the pump's output or in place of the thermostat to prevent the coolant from circulating at too high a rate and thus overheating the engine.

So removing the thermostat could very likely overheat your engine. Just because it didn't in your truck is just the luck of the draw.

Steve
'95 Clubwagon XLT

 

I think it would be fair to say that some racing cars do not use thermostats. The restrictor plates used in other racing cars is not there to regulate flow, it is to increase the pressure inside the block and head to increase the boiling point of their coolant.

Removing the thermostat is never the sole cause of overheating but can and will cause overcooling.

CLUBWAGON, the following is a long post that explains something about cooling system circulation. It's long, but it dispels some popular myths.


Think of coolant on a molecular level as it flows through the block, heads and the radiator. The layer of molecules against the metal experiences drag so it moves slowly. The next layer moves a little faster and the next faster still. Each successive layer moves faster than the one below it until you get to the middle of the passage, furthest from the drag of the wall. This situation provides very poor heat dissipation. This is laminar flow.

Accelerating the flow combats the problem of poor heat exchange. Speeding up the flow creates, more turbulence putting more of the molecules in contact with the tube wall where the heat is dissipated better. Another way of creating turbulence is to use dimpled tubes, which also helps to break up the laminar flow.

This principle also has to be kept in mind inside the cylinder heads where most of the heat is generated. If the circulation is a slow laminar flow in the hotter areas, particularly in the area of the exhaust ports and valve seats this is where trouble starts. When the engine is under load and those areas reach temperatures above the boiling point of the coolant the molecules of coolant in contact vaporize and create a layer of steam, which effectively insulates the metal from the coolant which creates a deteriorating condition. Too much steam allows the metal to get continually hotter, creating more steam which forces coolant out of the overflow and then you are into a serious overheating condition. The way to prevent this is to speed up the flow to generate turbulence, which will scrub away the steam bubbles while they are still at the molecular level. Cooling passages are, or should be designed to shoot high-speed jets of coolant directly onto the surfaces that tend to get hottest. You know that if you are towing and your engine begins to overheat, you pull over and run your engine at a very high idle. What you are doing by stopping is generating less heat. The fast idle rushes the coolant over the hot spots, scrubbing off the steam, which allows the hot spots to normalize. Everyone has had the experience of seeing someone stop and shut off an overheated engine and remove the radiator cap only to have the cooling system go into a nearly explosive boil over. In that case, they didn’t cool down the engine by running at fast idle, so once the coolant stops flowing, the hot spots create a mass of steam. Opening the pressure cap lowers the boiling point so even more coolant vaporizes, and boom. Second degree burns.

One technique that has been used to deal with the problem of hot spots in the heads is to replace the thermostat with a restrictor plate, which builds up the pump pressure inside the block and heads. Never do this. It works up to a point simply because it further increases the boiling point inside the engine. It is never a good idea. Coolant speed is the ideal cure. And every street engine needs the proper thermostat.

The steam from the hot spots, (and all IC engines have them,) are the reason that we have “degas” bottles in the cooling system. Or, “liquid/vapor separators,” or “surge tanks.” They help to insure that the steam is what gets ejected when the system is heat driven into an overpressure condition.

It is the common belief that the cure for a hot running engine is a radiator with more rows of tubes. It does work in some cases but not all. In an unmodified engine, the stock radiator is of adequate size. If the engine is running hot there is usually a defect that needs to be corrected.

In the event that a turbo is added, or other modifications are made that increase horsepower to any significant degree, the cooling system will require upgrades.

The first thing to consider is to go to a water pump that will increase the flow. When a high volume pump is employed, it is a good idea to use a cross-flow radiator with the pressure cap in the tank on the low pressure side, (the side with the lower radiator hose attached.)

A well-designed fan shroud, as opposed to no fan shroud, can increase cooling effectiveness as much as fifty percent.

Also in the interest of airflow, moving any other coolers away from in front of the radiator will improve airflow and remove the heat load of the other coolers.

If you are running a turbo, devise air exits to get the heat out of the engine compartment. This also creates a more negative pressure behind the radiator, increasing efficiency.

If it proves necessary to increase radiator capacity, try to get one with a larger surface area rather than adding rows of tubes. Also, there are very effective high performance radiators available with one or two rows of deep tubes and louvered fins. These increase efficiency without adding 'rows.'

If you go from two rows to four rows, you double the volume flowing through it. If you double the volume, you reduce the rate of coolant flow through the radiator by half, getting back into laminar flow which reduces the heat dissipating ability by a large percentage.
__________________

 

Well we can certainly finish this experiment by my putting the thermstat back into the van. First I will have to run another test run with the rebuilt transmission that is being put in today. I am on here to learn so I will accept that it can affect cooling and put it back next week. I guess it should have been obvious to me that if it worked for several years with the thermostat it still should work.

Thanks for the input....I appreciate your comments a LOT.

 

When I put in a new radiator I found my problem relative to overheating. The brass fitting that screws in the bottom of the radiator was clogged. Apparently this is where the temp sensor gets it water supply to measure. The hole in the fitting was about .200" and completely clogged. A rubber hose coming off of it was full of sludge. I blew it out. I went ahead and put the new radiator in and ran the vehicle under load today for 20 miles and absolutely no problem. With the thermostat out and temp 100F the water temp gage didn't go over N in Normal on the gage. Lesson learned. And I had the radiator flushed and rodded out yet they didn't notice the clog, and neither did I when the radiator was out the first time.

 

Glad you got it working.

But do run it with the stock thermostat. It will maintain the system at the proper temperature and it will reach it's proper operating temperature more quickly. A working thermostat will only raise the temperature if it is over cooling without one. A good thermostat will not cause overheating.