MM951

I'd imagine more water would be let thru, as there is no restriction in the hose..a fully open t-stat still takes up space in the rad. hose

Serge944

Anyways, does a new thermostat come with a snap ring? I dont think i have mine anymore.

KuHL 951

I tried that on a Miata for awhile and my mileage really suffered, the computer would run the car too rich. I don't think it's a good idea unless you have a long commute and get to normal operating temps which might not ever happen on a real cold day. My $.02 worth.

83na944

The system is supposed to pressurized at 100 kPa, IIRC. That's what's on the radiator cap. At that pressure the temperature of the water shoudl be about 120 C.

The amount of heat that can be rejected from the coolant is related to the temperature differntial between the coolant in the radiator and the air temperature. The higher the difference, the faster heat can be transferred to the air. So with lower temperature coolant, the heat is not transferred to the coolant and rejected in the radiator as effectively.

Right? Maybe some ME check me on this.

And, no, the retaining rings do not come with the thermostat.

Danno

"Someone said that the engine may run too hot without a thermostat as the water will be running through the engine too quickly. "

no... Heat transfer is a surface-area and time equation. The more time the coolant sits on the block, the more heat it will absorb. How fast you pump the coolant is irrelevant because some coolant is always in touch with the block.

"The amount of heat that can be rejected from the coolant is related to the temperature differntial between the coolant in the radiator and the air temperature. The higher the difference, the faster heat can be transferred to the air. "

YEs, but the final temperature will still be lower. So coolant at 220-F will shedd more heat to 70-F outside air, say down to 160F. But cooler coolant at 180-F, while shedding less heat (180-F -> 140F) will still result in cooler operating temps.

However, the main point that's missed here is not the coolant, it's the actual amount of heat the engine generates. If you have xyz-BTU per second, you need to get that to the radiator and transfer ALL of it to the surrounding air in order for the engine to run at a constant temperature. If the engine is cold and not generating that much heat, the thermostat holds it in the block to warm up the engine. By 170-180 degrees-F, the thermostat will be fully open and send full amounts of coolant to the radiator. The coolant typically is heated up further to about 190-195 degrees. At this point, the only variable is how much BTU per second can the radiator dissipate.

Serge944

Thats what my original hypothesis was. That not having a thermostat will not cause the engine to run hotter than normal in the end.

At operating temperatures, the thermostat isnt holding back any coolant flow, except for the space that it occupies. If there is no thermostat, i dont think the waterpump will be able to pump that much more water through. Regardless, the specific heat of the coolant will allow it to absorb a given amount of heat from the block, and then transfer it to the air through the radiator. There is only so much heat the coolant can absorb until there is an equilibrium within the block. This means that the slower its is pumped through, the more time the coolant has to reach is maximum heat absorbtion, and even pass its boiling point. If its pumped faster, you dont have to deal with that issue, and the same amount of heat is dissipated every second, due to the specific heat of the coolant.

From my limited physical perspective, the lack of a thermostat shouldn't cause overheating....because there is always a constant amount of coolant in the block, therefore heat dissipation should be the same regardless of the velocity of the coolant.

Ill still end up putting a new thermostat in eventually just for kicks...

Mongo

Serge, I still don't care what you tell me....whether we live in California or not. That thermostat is going into my car and thats final. Good your car runs without one and no problems.... Just as long as it runs good is the issue here. And I believe that my car will run best in its stock form. So, I'm gonna go by the book and do things right for a change...

Andy

ftanguay

You MUST have a thermostat! if you haven't (like danno said) the water flow will be too great. Your engine will take longer to heat, but it won't be able to cool down. I saw many people who have try it on race track and no one stick with that setup. The only trick you can do is make a hole in your old thermostat to slow down water flow (it only serve as a restrictor). In that case you will never have to bother about thermostat and your engine will never heat.

83na944

DAnno, don't you think the radiator is designed to dissipate heat faster than the engine can produce heat under normal cicumstances? Otherwise the engine would be doomed to overheat. Then the thermostat must open and close in normal operation to keep the temperature above the minumim temperature, not below the maximum temperature. So the point of the thermostat is to keep the engine temperature above a set point.

As Danno's example points out the the warmer fluid rejects heat better than the cooler fluid in the radiator. But in the pressurized cooling system the temperature is more like 230 F.

I agree the temperature of the coolant in the system with a thermostat will be warmer than a system without a thermostat. The same is true for systems with and without pressure caps.

However, the lower temperature coolant does not mean that the engine will operate cooler. The actual engine temperature could be warmer.

And you still have the issue of premature wear due to low temperature operation.

Dr. Porsche wouldn't have put a thermostat in the engine if you didn't need it. Note the lack of cup holders.

Danno

"DAnno, don't you think the radiator is designed to dissipate heat faster than the engine can produce heat under normal cicumstances?"

Yes. I think only under racing circumstances where you have dissipate an extraordinary amount of BTUs per second, that removing the thermostat would be needed. This will allow for faster flow of coolant out of the block before it gets heated up past its boilng point.

But in most circumstances, especially in the winter, the radiator can shed much more heat per second than required. Thus the thermostat is needed. Also be careful about excessive warm-up times. The tolerances are sloppy and parts don't fit well until fully warmed up, so you're risking more wear by having your engine run cooler for too long.

Serge944

Well...im convinced. I bought a new thermostat at kragen today. However, i am having the HARDEST time finding a snap ring and seal in that size anywhere. I dont have time to order it as i want it installed before the meet on staurday. Does anyone know of a place that sells them or does anyone have a spare somewhere in CA? Someone please help me out, i need to fix this by this friday!

Thanks,
Serge

Serge944

Nevermind! I stopped by a european repair place and they had some.

Thanks anyways!