Thermostat education please

[atomb]

Hoping to understand the marine thermostat a little better -
I pulled my thermosta housing off and found the thermostat to be in a stuck position. Im not sure if it was stuck open or in closede position but if it helps the thermostat was flush in with the bottom of the hiousing portion after pulling the cover off.

i understand that at 140 the valve opens to but why and what is happening in the cooling system-im running a raw water cooled engine. Thanks for any schooling i could use some

i do understand that the engine needs to release the 140 degree water so it doesnt overheat

 

[a70eliminator]

Re: Thermostat education please

Very simple, when the valve is close water can not flow, it heats up and begins to open allowing water to flow through the engine.
If you want to see it open then drop it into a pan of boiling water and observe what happens.

 

[Jeepster04]

Re: Thermostat education please

The whole purpose of a thermostat is to get the engine to running temperature. Typically an engine is very inefficient when its cold, thus the need for a thermostat. If water was allowed to constantly circulate through the engine it would never warm up. Even more so when the air(water in our case) is cold(winter).

 

[WizeOne]

Re: Thermostat education please

...The whole purpose of a thermostat is to get the engine to running temperature.......

...and to keep it at a constant temperature. Engines do not like it when they run too cool OR when a fluxuating temperature keeps changing the dimensions of the cylinder walls, etc.

Other than the temperature rating and the materials used, they are no different than an automotive thermostat.

 

[Don S]

Re: Thermostat education please

...and to keep it at a constant temperature. Engines do not like it when they run too cool OR when a fluxuating temperature keeps changing the dimensions of the cylinder walls, etc.

Other than the temperature rating and the materials used, they are no different than an automotive thermostat.

To add to what Wize One mentioned, DO NOT remove one to make the engine run cooler. It only makes you feel better, not the engine.
Even when fully open, a thermostat has a lot more restricted opening than if you were to leave the thermostat out.
BUT, without a thermostat, the water passes over the cylinder walls very quickly and basically doesn't go slow enough to absorb heat from the cylinder walls. Outwardly, you can touch the engine anywhere and it's cold. But, you can't touch the cylinder walls or the combustion chamber and feel the extra heat those areas are getting because the cooling water moves to quickly and doesn't pull heat from those areas.
So, for those that think they are helping the engine run cooler by removing the thermostat, wrong. Probably actually overheating the areas that shouldn't be

 

[swcolorado]

Re: Thermostat education please

Hoping to understand the marine thermostat a little better -
I pulled my thermosta housing off and found the thermostat to be in a stuck position. Im not sure if it was stuck open or in closede position but if it helps the thermostat was flush in with the bottom of the hiousing portion after pulling the cover off.

i understand that at 140 the valve opens to but why and what is happening in the cooling system-im running a raw water cooled engine. Thanks for any schooling i could use some

i do understand that the engine needs to release the 140 degree water so it doesnt overheat

How do you know your thermostat is stuck in one position? Put it in a pot of water and turn on the heat. It should start opening at approximately the number stamped on the thermostat. You can put a meat thermometer in the water to verify the temperature. Make sure you install a new gasket when you reinstall (or install a new one) back in your engine.

 

[QC]

Re: Thermostat education please

It should start opening at approximately the number stamped on the thermostat.

Yes, it is important to understand that this thing is not binary, as in on/off, they start to open at the stamped temp and are fully open usually around 12 degrees hotter. So you should see between 140 and 152 on an accurate gauge.

Also, probably the most misunderstood thing about thermostats is that they control minimum temperature and have almost nothing to do with maximum temp other than that 12 degree swing. If the engine overheats with a fully open thermostat of any temp it will overheat with a lower temp 'stat also. What Don posted about bypass is huge. When OEMs do cooling system audits, they use a permanently blocked open thermostat to determine the system's capability. Removal is never an option.

 

[atomb]

Re: Thermostat education please

Thanks guys for the terrific information. I really appreciate everyone who took the time to respond. I did test the thermostat -it didnt do anything when i heated the water up so I believe its shot. after i posted i checked the pdf for my engine and saw a page about the thermostat that is not in my older print copy that i have. It shined a light on the situation and you guys really put in perspective, thanks again.

 

[Dshow]

Re: Thermostat education please

I still do not understand what Don is saying about flowing to much water and not absorbing the heat... Wasn't this discussed a few weeks ago regarding riser temp? I thought the more water, the better?

 

[toger13]

Re: Thermostat education please

if the water flows around the engine too fast the water doesnt take any or enough heat away from it

alot of race engines do away with the thermostat and fit a blanking plate where it was with the same size hole as the thremostat would be open for this reason

its like if you touch a hot exhaust really quick you dont even feel its hot but if you leave your fingures on it for half a second it will melt your skin off dont try this it does hurt lol

Si

 

[Knightgang]

Re: Thermostat education please

Usually yes, but if it moves to fast, it cannot pull the heat out as the water does not have time to heat up...

 

[Aviator5]

Re: Thermostat education please

According to that "theory", when you ride your boat in cool air, you must feel much colder when you go really slow, and sweat if you going too fast, because the air does not have enough time to chill your face. Where did you guys get that theory anyways?

 

[fuzzybob]

Re: Thermostat education please

evaporation of the sweat cools your face..... apples and oranges

 

[Aviator5]

Re: Thermostat education please

OK, I got it, if you go fast than you sweat, and sweat evaporates and cools your face. It is not actually cool air that will chill you.
How about if you drop in a frigid water, shouldn't you stay calm in one spot in order to stay warmer ?
Because according to this theory you shold be running around like crasy so water won't have enough time to freeze you.

 

[mkast]

Re: Thermostat education please

Where did you guys get that theory anyways?

If you take a basic engine class, you might not have such a hard time understanding.

 

[Aviator5]

Re: Thermostat education please

If you take a basic engine class, you might not have such a hard time understanding.

Interesting, I thought basic course in fluid thermodynamics would be enough.
Apparently engines don't follow the common laws of physics. Learn something new every day.

 

[Jeepster04]

Re: Thermostat education please

A thermo class in college does not teach you common sense.. They teach you how to use numbers to try and solve everything possible.

So lets say you take a hot piece of metal and dip it in cold water for 5 seconds and take it right back out. Is that piece of metal going to cool off more if you dip it in the cold water for 10 seconds then remove it? Dont try to over think everything. Yes there is a point of no return where if the water moved too slow the engine would not be cooled properly.

And yes, the cool air will cool you along with evaporation(Ever hear of wind chill?????). Ever heard of a radiator in a car? Its cooled by air moving through it but once again, if that water moved through that radiator at super sonic speeds it wouldnt have time to go through a heat exchange.

 

[Rocky_Road]

Re: Thermostat education please

Interesting, I thought basic course in fluid thermodynamics would be enough.
Apparently engines don't follow the common laws of physics. Learn something new every day.

And apparently, engine designers for the last century somehow missed the course that you referenced...or it is the longest running conspiracy in automotive history, and all started by the thermostat cartel!

If thermostats weren't necessary, then the car manufacturers wouldn't spend the money to design, and install, around them...period.

I raise the motion that this thread has run it's course, and common sense is about to become the victim...so 'close me'!

Any seconds to the motion on the floor?

Happy boating!

 

[Aviator5]

Re: Thermostat education please

OK, I'll try to explain it as a mechanical engineer, who spend good part of his 30 year career calculating heat exchangers fo various machinery.
If you deep hot metal in the water and remove it, that will be a completely different story. But you have a constant water flow. And the faster that flow goes the more heat it will take away from the metal.
Now back to the basic engine class. The main purpose of thermostat is to keep angine running at constant working temperature. (Thermo - temperatute, stat - static). So when it closed it runs the culant along short loop (within the engine block) untill it warmes up, then thermostat opens a long loop that will include radiator (e.a. heat exchanger). And that is where the trick is. If you remove the thermostat the flow path will be unrestrained, and coolant will flow too fast, in another words it won't have enough time to spend in the radiator (heat exchanger) to cool down enough so it can do what it is supposed to do when it gets back into the block.

But anyways, thaks all, happy boating

 

[SuzukiChopper]

Re: Thermostat education please

in another words it won't have enough time to spend in the radiator (heat exchanger) to cool down enough so it can do what it is supposed to do when it gets back into the block.

Not all marine engines are closed loop systems which is where your arguments are coming from. The example of quenching hot steel applies to open loop systems (most marine engines), what you are saying applies to closed loop systems. Apples to Oranges.