Just got a data logger for my car; so I decided to monitor some parameters. One of the parameter is the coolant temperature. It got as high as 220+ degree F on a 95+ degrees day. The thermostat on the car has a rating of 180 degree F. Does it sound reasonable or is my car running hotter than normal? Thanks.
Thi
That's a little on the high side, but OK. 180 is the minimum temp and
240ish is usually the max.Thi Tran wrote:
Sounds pretty normal for any vehicle built in the last 20 years. the thermostat spec is merely its designed opening temperature, the rest of the system will determine what the coolant temperature actually modulates at...
The thermostat does not 'regulate' the temperature pe se. It is more to set a base temperature. 180 designation is the temperature at which it opens to allow the coolant to circulate through the radiator to be cooled. Even with a perfectly good operating thermostat, if the ambient temperature is cold enough it may never open. If the cooling system is not capable of removing the heat from the engine properly, the engine will over heat and turn the coolant to steam. The average operating temperature of the coolant can easily range up over 212 to 240, and most often does, in a pressurized system. The true engine temperature is much higher yet, ranging to 700 degrees around the valve seats. The most important aspect of a cooling system is the flow rate taking the heat away for the hot spots in the engine. The coolant actually flows around the hot spots as steam, steam removes many more BTU's than water when flowing in the same passage.
mike hunt
Hi Ran wrote:
Not unusual for driving at slow speeds or in stop-and-go conditions. That temperature is about when the cooling fan on many cars will switch on to pull more air through the radiator to cool it off..
That doesn't make sense to me. Can you explain how that can be? Water that is still 'water' can absorb a lot of btu's before it turns to steam plus it is more dense then steam. Once it's turned to steam it's lost density so right off the bat it would have less potential to cool for a given flow rate. And it no longer absorbs btu's like a heat sink but simply gets superheated. In addition, if you turn the water into steam you lose some of the control over pressure plus you may generate cavitation problems at the surface where it boils off. I can't see how steam internally in the engine could be anything but bad. Another thought that occurs is that the precise reason for pressurized cooling systems is to AVOID generating steam. If steam was good wouldn't we use "vacuum packed" cooling systems so they would more easily generate steam instead of pressurizing them?
Well, consider the source...*rolls eyes*
The thermostat regulates the *minimum* block water jacket temperature. Once it is wide open, it can't do anything else, except close when required.
And yes, they need to open, even if it's freaking *cold*. Combustion heat will not conduct through the block fast enough to prevent overheating. Ask anyone whose had a stuck closed thermostat.
I would think that pockets of steam forming around the hot spots would be somewhat detrimental to water jacket integrity as well.
nate
I sat in on a Mopar performance seminar back in 98 or99 during the Mopar Nationals in Columbus.
The guest speaker described the problems they had with the WOO car (a Kinser car IIRC) running on alcohol. Seems they couldn't keep the block and heads from frosting up, even
-without- a cooling system.
The fleet I worked for in the early 90s had a bunch of Plymouth Horizons w/2.2 engines, in the dead of winter (Wisconsin) the heater core with the fan blowing was sufficient to keep the engine cool. Not uncommon for the thermostat to -not- open after an extended drive. Talked to a Chrysler trainer that I knew because the drivers of these vehicles would complain about insufficient heater output, he said, "that's the way they are."
Basic physics, Assuming you understand BTU's, it requires one BTU to raise one pint of water one degree, 69F to 70F degrees standard, at (one atmosphere) sea level. It requires 850 BTU's to change one pint of water to steam at the SAME temperature at atmosphere. Even more BTU's are extracted when the water is under pressure as within the cooling system. It is the flashing to steam in the head that adds to the speed of the cooling effect. If it were not for this phenomenon an engine would require a much larger, faster flowing, cooling system. Contrary to you assumption, the relatively much colder steam still absorbs heat. It is that frasling/condensing effect that makes extremely high pressure forced steam circulation boilers possible and so efficient.
mike hunt
AZGuy wrote:
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