My 1994 z28 with 107,000 miles runs terrible and stalls after 10-15 minutes. I took it to a Chevrolet garage for a diagnosis and the mechanic sd. it has a leaky waterpump which is dripping onto the 'ultraspark' distributor. In addition, the mechanic sd. it has a bad head gaskets because he put a pressuer test on the radiator and the coolant flowed somewhere in the engine when it should not have done so. We don't know where it went.

My personal mechanic has taken the spark plugs off and didn't find any moisture, We don't smell coolant, the exhaust isn't smoky, the coolant isn't oily, the oil isn't wattery and no noticeable leakage from the waterpump. My mechanic wants to take the heads off to check for a crack or a blown head gasket.

My question is , why would the car run strong and perfect for 10-15 minutes and horribly after ? Is it electrical or internal ?

Sincerely,
Galen , Columbus, Ohio