MGB GT overheating only on motorway.

Asked by Angelolione66 Mar 10, 2020 at 08:36 PM about the 1969 MG MGB

Question type: Maintenance & Repair

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.

4 Answers


with the rad.cap is off,look do the fins look ****??...have you serviced the radiator?did it over heat quicker, slower or the same going down MOTORWAY with the thermostat out??? do you add water all the time? when hot are the rad.hoses staying open and not sucking closed..did you get all of the air out of the system? PUT a new 160o thermostat in it.. required to keep water in the radiator longer !! add 1 bottle of water the rad water...also dont run 100% antifreeze/coolant 40% af 60%water..

2 people found this helpful.

A simple thing to check before getting into more expensive solutions is the lower radiator hose. It may be collapsing under higher engine RPMs and restricting coolant flow. There should be a spring in the hose to prevent that, no idea what MGB used back in 69 though. After that you'll need to look for restrictions in coolant flow like worn water pump, gunked up radiator, etc.

1 people found this helpful.

Probably need a cooling system service. I would probably install a HD radiator and maybe an electric fan (will help around town). Use the product Water Wetter in the coolant which will help reduce operating temps. Tune it up because an engine out of tune can run hot.

2 people found this helpful.

I installed a new radiator and water pump. That fixed the problem for me. Check your belts too!

2 people found this helpful.

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