Coolant Questions Answered

21 replies to this topic
  • SUnruh

Posted November 06, 2001 - 02:18 PM


do you really think so?

i mean the engine only overflows when it reaches a pressure (temp related) where the cap lets it out.

now, let's change the cap so that it blow at only 10 degrees over optimum temp. if the engine don't puke, why do you need different coolant?

water boils at 212, but with some pressure can push that up to 220-230 before it blows.
so if your engine (in any motor) don't puke coolant, is it NOT already at optimum temp and not over it?

meaning, if you are not puking coolant, what more do you need?

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  • mikeolichney

Posted November 07, 2001 - 11:02 AM


The only time mine pukes coolant is whe its idling on a stand without airflow. I think when you are riding, you are not near the temps where the cap goes into its pressure relief function. The real question here is when you are riding is there any benefit to having your engine (cam, valves, piston, crank, etc) running a few degrees cooler. I don't know. I said I was just guessing.

My examples with the air cooled 125 and 930 engine are extreme. The 930 could be running a few hundred degrees hotter without the intercooler (the engines are oil cooled and so they don't boil over). I was just pointing out that higher engine temps (in the extreme) can cause quick wear. It was just something to back up my guess.

I was assuming that "optimum operating temperature" was the temperature at which the clearances in the engine due to thermal expansion were at their design specs. This is pretty loose because each clearance has a manufacturing tolerance, and so the temps could be different. This is also from a wear perspective, the optimum temp for power production could be quite different.

Its obvious that if you let your radiator boil over to the point it ran dry (say it was totally clogged with mud or something) the engine would get really hot, the Al piston would expand faster than its steel cylinder, and when all the tolerance was used up by thermal expansion, and it would wear really fast or seize. Whether there would be increased wear below this point is unclear (but probably more relevant). Like I said, I don't know, I was just guessing, and giving some reasons for my guesses.

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