A few days ago, I found a puddle of coolant on my intake manifold. The gasket for the thermostat housing was leaking, and when I took the housing off, I found there was no thermostat. I guess the guy who owned it before me thought it didn't need one. This made me think. Why don't all the guys who run 160* thermostats just not use one at all?

 

Because they keep the water from cirulating too fast (not enough time too cool off in rad.)

 

Well I was running mine without a thermostat for a while-but I didn't even know. I bought a 160* just to humor myself.

 

Don't you know how to type 160° ?

 

Haha. The stat is there to keep the coolant above a certain temp.

 

Time isn't involved. Proof is that maximum cooling occurs with the thermostat wide open, maximum coolant flow rate. Take the thermostat out and you get even faster coolant flow and even more heat loss in the radiator and thus LOWER coolant temperatures. I wish this wrong thinking would go away, but it shows up time after time.

 

A thermostat will allow the motor to heat up quicker reducing wear. Also in really cold temperatures, the motor will run too cold without the thermostat.

 

That is a good way to tell if your stat is stuck open. It will run cold.

 

Oh Boy another t-stat thread with both sides coming out before the first page is full.

Sorry jfb, your wrong. Gotta slow that water down in the rad to remove the heat. Pulling the t-stat will not make it run cooler. Thats a Fact, Jack!

Tell ya what, you pull your t-stat and run it hard. Then post your results.

 

I don't- how do you do it? Okay, so I'm computer-challenged.

 

We have had quite a number of C4 owners state what their coolant temp is running without a thermostat and YOU are totally wrong, their coolant temp is lower not higher! You need to take courses in heat transfer, thermodynamics, and internal combustion engine liquid cooling systems to finally understand that you get more cooling with increased coolant flow. By your wrong thinking, thermostats should increase coolant temperature when they open more and of course the opposite occurs.

 

100% correct!

 

Soon as I learn how to capitalize a period Ill get the degree thing down right?

I agree with JR...now I havent done this in a C4 but have in other cars, and removing the thermostat when driving hard or cruising at rpm (unless it was super low using OD) the car heated up every time eventually. If everyone else wants to argue go for it.

 

Soon as I learn how to capitalize a period Ill get the degree thing down right?

I agree with JR...now I havent done this in a C4 but have in other cars, and removing the thermostat when driving hard or cruising at rpm (unless it was super low using OD) the car heated up every time eventually. In my current car it likes to cruise at 3000 rpm without a thermostat I guarantee the fan couldnt keep up with cooling it down.

 

The engine produces more heat energy than the radiator can remove. Our C4's have radiators that are designed to run with a given flow restriction at the t-stat (wide open). Removing this restriction will not allow the water enough time in the radiator to exchange the heat. Although it takes longer to warm the engine, once it gets hot it will not cool off.

My DD had a busted t-stat and would run cold when putt'n around town. But when out on the road and the engine was making heat, it would always overheat once the speed was reduced. After replacing the t-stat it heated up to op temp in a few minutes (closed loop) and maintained that temp no matter how fast or slow I was going.

Thats why I know.



Oh please don't school me on thermodynamics, its real world experience that proves the theorys.
So until you pull YOUR t-stat and post the results here it's nothing more than :

 

That's peroid.

 

I kinda thought making a thread with that title would make a mess. Oh well, I guess that makes me a troll.
Anyways, I'll give you guys my 2 cents when I put everything back together.

 

If our engines make more heat than the radiator can get rid of, coolant temps would do nothing but continue to rise the whole time we were driving and that does not happen. You are dead wrong!!!!
Again, time spent in the radiator isn't a factor, what is a factor is the RATE of heat transfer both in the engine and in the radiator. The rate of heat transfer is determined by the temperature difference, not the flow rate. No matter how fast the coolant is flowing in the radiator, the BTU/second is determined by the difference in temperature between the air passing through the radiator and the coolant temperature, all other things being constant (air passing through the radiator at constant speed). Your statement that without a restriction (no thermostat) the engine takes longer to warm up is opposite your claim that no thermostat causes overheating. If your wrong theory is correct, the engine would take less time to heat up not longer.
Also, you have it backwards about thermodynamic theory and real world experience, it is the thermodynamic theory that explains what you observe in the real world, not the reverse.
When the radiator gets rid of heat as fast as the engine makes heat (rate of heat transfer), the coolant temperature will be constant.

A pot of water on the stove will boil in less time if the water is stirred compared to letting it sit still. Your theory says it will boil in less time if you don't stir it. You need an education in both thermodynamics and heat transfer.

 

Automotive
Main article: Wax thermostatic element

Car engine thermostatPerhaps the best example of purely mechanical technology in widespread use today is the internal combustion engine cooling thermostat. These are used to maintain the core temperature of the engine at its optimum operating temperature by regulating the flow of coolant to an external heat sink, usually an air cooled radiator. Also, research in the 1920's showed that cylinder wear was aggravated by condensation of fuel when it contacted a cool cylinder wall which removed the oil film, and the development of the automatic thermostat in the 1930's provided a solution to this problem by ensuring fast engine warm-up[3].

This type of thermostat operates mechanically. It makes use of a wax pellet inside a sealed chamber. The wax is solid at low temperatures but as the engine heats up the wax melts and expands. The sealed chamber has an expansion provision that operates a rod which opens a valve when the operating temperature is exceeded. The operating temperature is fixed, but is determined by the specific composition of the wax, so thermostats of this type are available to maintain different temperatures, typically in the range of 70 to 90°C (160 to 200°F). Modern engines run hot, that is, over 80°C (180°F), in order to run more efficiently and to reduce the emission of pollutants. Most thermostats have a small bypass hole to vent any gas that might get into the system, e.g., air introduced during coolant replacement, which also allows a small flow of coolant past the thermostat when it is closed. This bypass flow ensures that the thermostat experiences the temperature change in the coolant as the engine heats up; without it a stagnant region of coolant around the thermostat could shield it from temperature changes in the coolant adjacent to the combustion chambers and cylinder bores.

While the thermostat is closed, there is no flow of coolant in the loop allowing the combustion chambers to warm up rapidly. The thermostat stays closed until the coolant temperature reaches the nominal thermostat opening temperature. The thermostat then progressively opens as the coolant temperature increases to the optimum operating temperature, increasing the coolant flow to the radiator. Once the optimum operating temperature is reached, the thermostat progressively increases or decreases its opening in response to temperature changes, dynamically balancing the coolant recirculation flow and coolant flow to the radiator to maintain the engine temperature in the optimum range as engine heat output, vehicle speed, and outside ambient temperature change. Under normal operating conditions the thermostat is open to about half of its stroke travel, so that it can open further or reduce its opening to react to changes in operating conditions. A correctly designed thermostat will never be fully open or fully closed while the engine is operating normally, or overheating or overcooling would occur. For instance,

If more cooling is required, e.g., in response to an increase in engine heat output which causes the coolant temperature to rise, the thermostat will increase its opening to allow more coolant to flow through the radiator and increase engine cooling. If the thermostat were already fully open, then it would not be able to increase the flow of coolant to the radiator, hence there would be no more cooling capacity available, and the increase in heat output by the engine would result in overheating.
If less cooling is required, e.g., in response to decrease in ambient temperature which causes the coolant temperature to fall, the thermostat will decrease its opening to restrict the coolant flow through the radiator and reduce engine cooling. If the thermostat were already fully closed, then it would not be able to reduce cooling in response to the fall in coolant temperature, and the engine temperature would fall below the optimum operating range.

Double valve engine thermostatEngines which require a tighter control of temperature, as they are sensitive to "Thermal shock" caused by surges of coolant, may use a "constant inlet temperature" system. In this arrangement the inlet cooling to the engine is controlled by double-valve thermostat which mixes a re-circulating sensing flow with the radiator cooling flow. These employ a single capsule, but have two valve discs. Thus a very compact, and simple but effective, control function is achieved.

The wax product used within the thermostat requires a specific process to produce. Unlike a standard paraffin wax, which has a relatively wide range of carbon chain lengths, a wax used in the thermostat application has a very narrow range of carbon molecule chains. The extent of the chains is usually determined by the melting characteristics demanded by the specific end application. To manufacture a product in this manner requires very precise levels of distillation, which is difficult or impossible for most wax refineries.

 

If I need to remove 25000BTU/10secs and my radiator and ambient conditions allow me to remove 26000BTU/10secs, what happens if I speed up the flow and the coolant only spends 8secs in the radiator?

My math says:
NEED: 25000 x 10 = 250,000 BTUs removed
GETTING: 26000 x 8 = 208,000 BTUs removed

42,000 BTU back in the engine.

I guess I'm not sure how we can use a metric with a time element and then say the amount of time in the radiator doesn't matter. It may not matter for the transfer rate, but it seems to matter for actual cooling.