MGB GT overheating only on motorway.
Hi everyone. I've just purchased a 1969 MGB GT. Would anyone know why the engine over heats on the motorway but doesn't around town. I even removed the thermostat but it still overheated the engine, soon as I got to city driving the temperature was perfect. The head gasket shows no signs of being the cause, oil filler cap is clean. The gages work correctly because it was steaming aand the engine required a gallon of coolant. Could it be the water pump? The car has rarely been driven for many years before I bought it. Thank you in advance for your help.