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Hello All,
I have a 1996 850 GLT wagon (manual) with 305,000 on the odometer. Approximately a week ago, I noticed a crack that ran almost the entire circumference of the plastic radiator cap. It looked as though some one had taken a knife and ran it along the edge at the top of the cap. Coolant was escaping through this crack. Basically the very top of the radiator cap had separated from the lower bottom. I figured the cap had just spontaneously failed and purchased another Volvo radiator cap and thought nothing more of it. The leak had not caused the car to overhead. I just happened to notice the coolant residue around the expansion tank.
A week later I am looking at the expansion tank, and I noticed the top of the tank where the cap screws on it “bulged” upward. The radiator cap is no longer flush against the expansion tank, but instead is raised upward. I also noticed a stress crack developing in the expansion tank where the “upward bulge” has developed. The expansion tank and the radiator cap are not leaking, but the expansion tank looks light it about to explode.
Some background information. I flush and replace the coolant once a year. The engine is not running hot according to the temperature gauge. In fact it is “dead center” with the position of the temperature needle as it should be. I have not replaced the thermostat on this car in several years, because I saw no indication it was not functioning properly. Yet I know, based upon the radiator cap that failed, followed by a “bulge” that developed in the expansion tank after I replaced the radiator cap, it appears that excessive pressure is building up in the cooling system. Also, the coolant level is at the the level it should be, so there is not excess coolant in the system.
Does anyone have any idea what could be causing this excessive pressure in the cooling system? My fear is I may blow a head gasket, or water hose or cause the radiator itself to fail if I don’t fix this problem. Yet all I see is the symptoms, but not the cause of this problem.
Thanks to all who reply.
Hugh
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