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If the engine isn't overheating and the coolant is coming out, we need top check for a bad head gasket. It sounds like compressed air from the combustion chamber is getting into the cooling system and causing this.
Take a look through this link and let me know the results.
As far as the water pump working, if the engine doesn't overheat, it is working.
Let me know the results of the head gasket test.
Friday, April 26th, 2019 AT 8:28 PM