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MG MGB GT V8 Factory Originals Technical - Engine Overheating?

I have a 3.9 litre Rover V8 in my 1980. The temperature gauge in the car says the engine is running hot. My mechanic says it's not, the gauge is not accurate.

What is the correct running temperature and what is the best method for measuring it?

Richard Cohen

PS: I'm the guy who couldn't decide to keep or get rid of my B. After an all new electrical harness, I'm keeping it with a smile on my face.

I have a 90" thermostat in my GT (3.5) and it never moves from that temp summer or winter.
Peter (TC9356)
Peter Malkin

We give a great deal of credence to the readings our gauges give us. I have 2 V8's, one a 3.9, the other a 3.5. The cooling and lubrication systems on both are identical, and there are no other issues which might affect running temperatures. But the capillary temp gauges give completely different readings. One sits at 5.30, the other at 7 o'clock. These gauges are not stunningly accurate! If it's not boiling and losing coolant then it's probably OK. But if you need to know buy or borrow an infra-red gun and point it at the inlet manifold where the sender unit is when up to temp.
Allan Reeling

Come on Richard, let us know what's happening!
Allan Reeling

"But the capillary temp gauges give completely different readings."

I've had that with two different gauges on the same car.

However I'm wondering if this uses an electric gauge, as it is based on a 1980, and presumably the engine is later than the factory V8s. There were three different gauges and three senders over the life of the MGB. The first change occurred at different points for each (North American cars), indicating they they were compatible. But the final change (when the UK got the electric temp gauge) they both changed together. The senders have different coloured insulators, the final one was black, the earlier two probably red. Get the wrong combination and it can read either high or low. Someone recently with the same issue had his reading N at switch-on, and H when up to temp.

As Allen says if it isn't steaming or losing coolant it is probably OK, and an infra-red thermometer will tell what it actually is.

This thread was discussed between 06/07/2016 and 22/07/2016

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