It takes a lot of heat to take the temper out of a spring... around 750 degrees F. The molded plastic end caps seem to be made of nylon. Nylon melts around 300 degrees F. The molded caps would be melting long before the springs lost their temper. I think the brush was sticking in its' cavity... just a guess.
As I said previously, I need to see more failed pumps.
This weekend, I will place thermocouples on the fuel pump body and in the fuel return bucket. If it ever stops raining here, I can take a long ride and record the results.
I think the only way to overheat the pump is to run it dry. And most likely, the bearings would begin to seize and cause an increase in the current demand causing the appearance that the motor over heated for other reasons. The fuel circulating through the pump should keep it well within it's safe operating temperature.
I believe that the theory of wrapping the fuel lines with insulation is a hold-over from the days of carburetors, when fuel lines ran close to hot engines and caused vapor lock. At atmospheric pressure, automotive fuels will boil at temps. between 100 and 400 degrees F. The wide range is due to the various additives used. With fuel under 58 psi pressure, there is no chance of the fuel boiling and causing vapor lock. Higher pressure, higher boiling point. Lower pressure, lower boiling point.
And, with the fuel sloshing around in those big, heat-sink aluminum tanks, how can the fuel heat up so much to cause damage. Put your hand on the fuel tank after a long run... see if it's hot.
