What temp is too hot?

[cbouton]

Finally got my new setup out on the snow and conditions were 28-32°F ambient and snow was soft 6" on top of semi firm base, not much loose throwing up and my temps were running 195-205°F . When they got to 200 I'd find a more open area to increase my speed to bring temps back down too around 190. Bike setup is 21 GasGas EX450F with thermo bob 180° and PST engine jacket running a Riot 3 Pro. If I tried to go slower in 1st gear temps would go right over 200. About an hour into the ride had to stop and tighten my chains so I went ahead and removed the engine blanket and temps were still in the 195-205 range rest of the day. Thinking about installing a fan kit for slower riding. My question is what temp is too hot? I did a search but all threads appeared to be about getting temps up, not what the upper limits should be.

 

[eric82930]

As long as it's not boiling and puking coolant it's fine. With a standard radiator cap it won't boil until at least 220. High pressure caps and fancy coolant will raise it even more but be ware some fancy coolant will freeze!

 

[byeatts]

Water boiling temp is 220, Coolant adds much higher boiling point and cap adds even higher boiling temp. 240 degrees will not boil coolant regardless of cap.

 

[needpowder]

Also depends where your temperature is being read at. My thermo Bob is a couple inches up from the head and I feel like the readings are about 10 to 20° off. For example if I am at 180 on my gauge my temperature might be 200. Sometimes I hit 220 to even 240 on big climbs when I’m not paying attention to the gauge. Usually spit some coolant out at those temperatures. I often pack my Engine jacket full of snow when I know I’m going to be climbing long distances. And conditions this year we’re strange. I rode most of January and early February without an engine jacket at all and still had to kick snow on my engine often. This is on my Yamaha. My buddies on Husqvarna and KTM seem to run cooler.

 

[M5-]

Water actually boils at 100C or 212 F. I don't start to get too excited until I see 235-240, normally it doesn't get that high but it happens. 1.8 Bar rad cap and Engine Ice it wont push coolant even at those temps. Hey Portgrinder I know you're just dying to jump in on this one. LOL

M5

 

[byeatts]

Also depends where your temperature is being read at. My thermo Bob is a couple inches up from the head and I feel like the readings are about 10 to 20° off. For example if I am at 180 on my gauge my temperature might be 200. Sometimes I hit 220 to even 240 on big climbs when I’m not paying attention to the gauge. Usually spit some coolant out at those temperatures. I often pack my Engine jacket full of snow when I know I’m going to be climbing long distances. And conditions this year we’re strange. I rode most of January and early February without an engine jacket at all and still had to kick snow on my engine often. This is on my Yamaha. My buddies on Husqvarna and KTM seem to run cooler.

spitting coolant out at 240 is not from boiling , its simply expanding fluids and pushes the extra volume out because it was filled to the top , many see 260 often and no boil at all . Evens coolant has boiling point of 375 degrees. pure water will have a boiling range 212 to 225 depending on the dissolved oxygen content .

 

[M5-]

What is the maximum boiling point of water?


212°F

Increasing the temperature above the boiling point, 212°F (100°C), causes water to change from liquid to gas (water vapor). The melting/freezing and boiling points change with pressure. The boiling point of water varies with atmospheric pressure. At lower pressure or higher altitudes, the boiling point is lower.


I'm calling BS, where do you come up with this stuff, honestly, we learned this in high school, or maybe it was junior high.

M5

 

[Sheetmetalfab]

What is the maximum boiling point of water?


212°F

Increasing the temperature above the boiling point, 212°F (100°C), causes water to change from liquid to gas (water vapor). The melting/freezing and boiling points change with pressure. The boiling point of water varies with atmospheric pressure. At lower pressure or higher altitudes, the boiling point is lower.


I'm calling BS, where do you come up with this stuff, honestly, we learned this in high school, or maybe it was junior high.

M5

Altitude changes the boiling point.

Your definition is only true at sea level.

Hence why you see baking instructions having a high altitude alternate set of cooking instructions.

 

[eric82930]

So true about cooking. Baking stuff is tough sometimes. Water boils in my house at 7k below 200 degrees so everything bakes at 12 deg less than sea level until all the water is cooked out.
The puke point in a bike is totally dependent on kind of coolant and cap pressure. And expansion of an overfilled system has nothing to do with boiling point. Also keep in mind the cap blow off pressure is reduced by .35 bar at 10k. Most single track riders at high altitude change the cap to something higher to compensate for the low air pressure.
Also know that until most of the coolant is gone from the engine block the core engine temp won't go above the boiling point.

 

[needpowder]

At what temperature do you think we’re actually doing damage to the engine?

 

[eric82930]

At what temperature do you think we’re actually doing damage to the engine?

 

[eric82930]

Some people believe that if your coolant is too hot then your piston will run hot which is true but lean fuel mixture from our friends at the EPA create way more heat in the piston than any change in coolant can create.
From everything I've seen, there is no damage being done until most of the coolant has puked out and the water pump stops circulating. After that it could warp the head or burn the valve seals but the oil is usually good to 400° so bearings and such easily survive.

The only damage I've ever seen was from blown hoses with zero water left.

 

[tchriste]

I run a 2020 KTM 450 and I see 195-205 while playing. on trail I see 155-165. Big hill pulls she'll climb up higher. deep pow she runs cool about 148-160. My manual says max is 238 with stock coolant and rad cap. I run a fan set at 95c but the fan sensor is at the top of the rad and the temp guage is located at the thermostat so there's a difference to adjust for, the heated handlebars also play a roll below thermostat setting. Hope that helps.

 

[dooman92]

needpower, that is a good question. But, there are other factors than just coolant temp that affect the max temp without damage so it is difficult to point to a certain temp. Given that many critical parts in the engine are cooled by the oil, oil temp is a part of the equation. As we know slipping the clutch heats the oil. From what I read from engineering studies and conversation with two GM engineers oil temps between 200F and 250F are best for longevity. Most synthetic oils start to experience therma break down just south of 300F. I know from experience that vehicles operating with coolant temps at 210-215F vs less than 200 last much longer. I worked as an auto tech at the advent of exhaust emission systems. We found higher coolant and combustion chamber temps reduced hydrocarbon emissions and extended engine life. That 210F thermostat in your truck is one off the reasons we have so many 200-300K mile engines. So, if oil temps are less than 250F I am comfortable with coolant temps of 240ish or more for short periods and 200-210 average. Fwiw, I have oil temp gauge on both my bikes and in no snow dust conditions on trail I see oil temps 250-260 periodically and I do not slip the clutch. In the snow oil temps seldom hit 200 so in the snow the oil is doing alot of cooling and elevated coolant temps would be less of a concern. This is assuming that the system has either high boiling point coolant or a properly pressurized system and boiling of coolant is not taking place. I run evans coolant to eliminate that potential for boilover.

 

[wwillf01]

My 450sxf runs best 200 to 220… I would not worry till 235 and above but I run Evans also.


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[eric82930]

I would agree one aspect of the whole debate is wondering how to make the engine last the longest life span possible and the other aspect is when instantaneous catastrophic damage occurs.

Longevity has never been the engineering goal for mx bikes with 100hr rebuild requirements and if longevity was the main goal then we should Never slip the clutch or hit the Rev limiter but where's the fun in that?
If my bikes are still making compression and don't sound like marbles in the engine I don't worry about much until the cartographic failure occurs which isn't often and I ride a lot. Snow bikes are much less trouble than my 2 decades of sleds in my experience the sleds blew every season even with the best maintenance.

 

[byeatts]

So true about cooking. Baking stuff is tough sometimes. Water boils in my house at 7k below 200 degrees so everything bakes at 12 deg less than sea level until all the water is cooked out.
The puke point in a bike is totally dependent on kind of coolant and cap pressure. And expansion of an overfilled system has nothing to do with boiling point. Also keep in mind the cap blow off pressure is reduced by .35 bar at 10k. Most single track riders at high altitude change the cap to something higher to compensate for the low air pressure.
Also know that until most of the coolant is gone from the engine block the core engine temp won't go above the boiling point.

The expansion of liquid absolutely causes coolant to spit out, That's why the suggested fill line is at the radiator fin level. Many factors alter boiling point ,atmospheric Pressure , system pressure and the molecular makeup of the fluids ect , Its not an absolute temp in which water boils .