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dyates773 -> Northstar Coolant Loss (5/22/2007 3:35:01 PM)
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Many thanks to all of you who have repeatibly posted your comments on the well known issue of Northstar headbolts losing thread integrity in the block leading to head gasket issues. I own a 1998 Seville STS with 194,000 miles. The car is in excellent condition except...... at sustained highway speeds the coolant is forced out of the coolant tank cap. The car will overheat when the level drops enough to stop flowing or gets "air bound". This car is in good enough condition to drive everyday, runs great, but cannot be driven at sustained speeds over 60 mph. Its age and condition does not warrant installing a long block or a major teardown on such a high mileage engine, the cost alone would be more than the car is worth. For those of you in my situation I have engineered a less than perfect but workable solution. My thinking was how to vent the exhaust gas and pressure to prevent forcing out the coolant. Being a Chemical Engineer I'm very familar with industrial hot water systems. Many of these systems cannot tolerate air in the piping. Most of them have air vents in the piping system. They are high pressure and high temperature. I have installed a 1/2" NPT float type air vent into one of the cooling system bypass hoses that now vents the trapped combustion gases. The vent is rated at 50 PSI and 250'F. It has worked for over 1000 miles in the last month. It does not pass liquid, only air. Today I drove home on the Interstate at 70MPH for over 40 miles with an outside temperature over 80 degrees. No overheating. I will post a picture if there is any interest. Good luck.
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