Headbolts "On the Boil?"
07-18-2014, 03:04 PM
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C63AMG, NIssan NX2000, Pontiac Fiero GT
Headbolts "On the Boil?"
The recurring pictures of the removed headbolts has one common feature:corrosion . Most are not broken. This forum has discussed breakage from several views: (1)defective headbolts (2) weak headbolt design (3) corrosive coolant. Forum member "Critter" has interested me in reading more on coolant additives, taking me into another view: "local boiling." (Yes, raving on again...) Experts views suggest the following.
Coolant can boil at its calculated temp. The water vaporizes and insulates the affected area from coolant, further heating it. Dissolved oxygen can be released , attacking metal (headbolt rust).
C 63 headbolts shoulders (tops) are recessed , out of coolant flow. WOT may produce "local boiling" on and off the track. Heat soak after shutdown raises hotspot temps further. (Lotus Elise K engine cars use ECU controlled supplemental water pumps to address this). I have noticed the dash coolant gauge does not follow the oil gauge . Yesteday the coolant temp said steady 197F, while the oil swung from 208F to 235F climbing hills home. Is "local boiling" undected?
Coolant can boil at its calculated temp. The water vaporizes and insulates the affected area from coolant, further heating it. Dissolved oxygen can be released , attacking metal (headbolt rust).
C 63 headbolts shoulders (tops) are recessed , out of coolant flow. WOT may produce "local boiling" on and off the track. Heat soak after shutdown raises hotspot temps further. (Lotus Elise K engine cars use ECU controlled supplemental water pumps to address this). I have noticed the dash coolant gauge does not follow the oil gauge . Yesteday the coolant temp said steady 197F, while the oil swung from 208F to 235F climbing hills home. Is "local boiling" undected?
