How high of a water temp can engine get and be deemed safe?

[dirty hippie]

It's been triple digit hot here in the Los Angeles area. A couple of times I was on the freeway and hit pre-rush-hour traffic or just a congested portion of the freeway in which traffic slowed to a crawl and even at times to stop-n-go. As usual, I monitor my SG2 with water temp readings as one of the four readings. Usually my car cruises at 193-195-deg F. But in heavy slow or stop-n-go traffic after driving at 55-60mph, I see that the temp readings slowly go up, first to 197, then 198, with highest being 206. No A/C on. However, the temp never really stays in the 200 range temp for long. Usually it goes back down when I see a gap and speed up a bit to rush air into the "grille." Once traffic frees up and I can go at speeds, temp goes back down to a comfortable 195. I think water boils at 212, and I think I read somewhere that the fan kicks in at 212. Do you guys drive with water temp in the 200 range often? What has been your experience in driving in hot weather in slow traffic--no load, just lack of airflow through the engine bay area?

[Eli]

The temperature that a liquid boils at is dependant on the pressure it is subjected to. For example, at sea level and under 15PSI of pressure, plain water doesn't boil until 252ºF. At sea level, the air pressure is 14.7PSI and water boils at 212ºF.

The coolant system in an automobile is closed to allow pressure to build. Further, you shouldn't be running straight water in a modern automotive coolant system - antifreeze is necessary even if you don't ever see freezing temperatures as it has corrosion inhibitors and lubricants for you water pump. Antifreeze both lowers the freezing point of water and increases it's boiling point. With a 50/50 ethylene glycol/water mix, the boiling point of the liquid is 225ºF at sea level.

The radiator fan comes on at 206ºF. The highest I've seen my coolant temperature is 217ºF, after climbing a long, steep grade. Over 240ºF, and you're starting to get into problem territory.

The thermostat keeps the coolant temperature between 193ºF and 198ºF with adequate radiator airflow.

As a side note, this phenomenon is why things cook differently at higher elevations. For example, I'm at 7,000' in elevation. The air pressure up here is only 11.3PSI. This causes water to boil at only 198ºF, which in turn causes you to have to cook things like pasta longer because of the lower temperature.

[Leeper]

Water boils at 212 at sea level with no pressure, your engine HOPEFULLY has coolant/anti-freeze which raises the boiling temp considerably so no worries about it handling the heat. If your temp gauge on your car goes over 1/2 then you have engine cooling issues.

[Varak]

I'm in Phoenix and my 'normal' water temp during the summer is around 203. Under heavy load it will go above 210, but drops back quickly. During the winter (or at night) it is around 198.

[ackattacker]

The engine is essentially safe from heat damage as long as there is coolant in it and it's circulating. Don't worry about it unless the coolant starts boiling out. I drive an air cooled VW Bus that routinely sees cylinder head temps over 400F and Oil Temp up around 240!!!

[Leeper]

Ackattacker - you are comparing apples to oranges here. Air-cooled cars are completely different in their tolerances than are water-cooled. DH - if your car gets anywhere near the red area on the water gauge then you are in trouble. If it routinely gets over half for any period of time your car has issues that needs to get addressed. I can drive my Insight in well over 100 degree temps in any sort of traffic and it will never reach half.

[Eli]

His comparison is valid - in the right context. He's saying that as long as there is coolant in the engine, it's not possible for it to overheat. This is pretty much true. The problem is that when the coolant reaches a certain temperature it begins to boil, raising the system pressure to beyond what the radiator cap is designed to hold. That's when you end up with the classic "steaming hood" syndrome. At this point, you have no/little coolant left and engine damage is imminent.

Air-cooled represents worst case scenario. Our cars will never see temperatures like that, at least I hope. Technically, the tolerances are roughly the same. It's just that a water cooled engine overheats VERY rapidly once coolant is lost because of the low surface area of the engine.

The other problem is that the Insight's temperature gauge completely sucks, unfortunately. Like the other gauges, it doesn't give you a good indication of what is actually happening - in this case, coolant temperature. Notice that it starts at 2 bars, jumps up to four bars at around 120F, then finally to six bars at 160F. Note that it doesn't change again until at least 220F, and probably much higher than that. Not something I want to test, at any rate.

If you see the gauge above six bars, something is wrong. Don't wait for it to climb any higher....

[dirty hippie]

Leeper, as far as I know, the car is using 50/50 pre-mix coolant. I don't think it's Honda stuff but Prestone green. Temp gauge on car never goes pass 6 bars, and I keep an eye on that and not just the SG2. My question was how often or if it's even accepatble to see temp reach the 200 range. It seems like normal operating temp for my car is 193-195, but just have seen it reach up to 206 for very short periods while crawling in traffic on a hot day with no to little engine load and little airflow to the radiator.

Btw, I'm surprised how quickly the gen 1 gets to operating temp and also how quickly it cools off.

Btw, Leeper: "I can drive my Insight in well over 100 degree temps in any sort of traffic and it will never reach half." What do you mean by this?

[Eli]

Seeing over 200 is completely normal, again the radiator fan doesn't turn on until 206 degrees.

For how much coolant the engine holds and how big the engine is, I think it actually takes a long time to reach operating temp. And this is with purposefully engineered coolant passages around the exhaust ports....

It's because of how efficient our engines are. Truly incredible efficiency for a gasoline engine.

Leeper means half on the temp gauge, but like I pointed out if you see it above 6 bars stop immediately and check things out.

[Willie Williford]

FYI
For a learning and maybe entertaining scenerio about the efficency of the cooling system in the Gen 1 Insight you might want to read page 26 of the thread "Turbocharged Insight".
(Don't try this at home without adult suppervision)
HTH

Willie