Cast irons and some steels have a much worse time (warpage/breakage) of being 'quenched' in cold water than aluminum. I'll pass on any thermodynamic comparisons of water and air, after all hot water freezes faster than cold water Don't'cha Know! [img]i/expressions/face-icon-small-happy.gif[/img]

 

I think that I need to add a little something. Driving your car down the road does cooler your engine. Thats why the have radiators. The water pump curculates water through the radiator and the air coming in through the grill pass though it. This effect would be most noticable on a hot day, if you have a good temp gauge and you had left your car idle in the driveway for a while. Take a look at the temp gauge when you jump in and look at it again when you have drove a few miles, You will notice that the temp has dropped. As far as the orginal post, I have heard people tell me that it would hurt a hot motor to dip it in water, but I have never seen it happen. I think it just is a old wives tale.

 

bigfish, i know that driving your car down the road will cool your engine better, but the question was asked of how come your car will overheat if you drive it down the road with no coolant in it.

 

I love talking physics, Zukiscott, I think you have this backwards.

Water is a way more efficient than air in removing heat. Now the part where you have this wrong is where you stated that if you let an engine sit in 40 degree water and one in 40 degree air, the air cooled engine will be cooler. This is true to a point but only in standing water with no current at all. Add the slightest current and the 40 degree water will cool the engine of quick.

Dive suits are a good example. If you stand out in 40 air naked, you will be cold and uncomfortble but you will be OK. Jump in a 40 degree pool of water and you will die of hypothermia within the hour. Why becaue the water is a much better conducter of heat and will pull the heat away from the surface of you body very efficiantly. Now jump in the 40 degree pool with a divesuit, at first the water will be very cool, but wthin a few minutes your body will warm the water inside the suit. Since the warm water inside the suit is trapped you will warm up, like the hot engine sitting in perfectly still standing water. But how often does an engine sit in perfectly standing water, never.

 

rob, i agree with you about the moving water, but the same could be said for moving air. if you go stand outside naked in 40 degree weather with a stiff wind then your body temperature will also be lowered over time. also, if you jump into freezing water you will get hypothermia, just as you are naked outside in the wintertime, but you will die within an hour in the water becuase your body will slow and you won't be able to swim and you will drown. i know that you will never have your motor sitting in standing water, but that was the only way i could think for greatcanadian to test what i was saying. also, how often is your motor just sitting in idle air, never, there is always air current. i'm not saying your wrong and i'm right, i'm just saying we were looking at it in two different ways, you are right about moving water cooling a motor, but i am also right about moving air cooling a motor just as efficiently.

 

To prove my point about about water removing heat better than water. Take a nail put it under a torch until it is bright red. Now dip it in 40 degree water. The water will cool it so fast that your could immediatly handle the nail bare handed.

Now take the same nail, heat it up again and now put it in a 40 degree (air temp)room or box. It will take about 4 minutes before you could handle the nail bare handed.

Now what is more efficient at removing heat?

 

I'd never thought I'd agree with someone from Dade county again after recent events. That's a very practical demonstration trx250rob, but I doubt that'll sink in for a nother east coaster.

 

This is what can happen hot engine, cold water and hot differentals the sudden cooling of hot parts will pull water into them thought the seals.I know this from my four wheelen days the rear axle on my truck did it all the time I'm not talkin a quick splash but a long water crossing.When you change the lubes and it comes out milky white you know some water got in.

 

yes actually be careful when cold water hits ur hot motor the tempature decrease makes the head despand so fast it causes cracking..when a motor is hot it needs time to go down metal isnt very flexable man