MG Car Repair: Water temp. Gauge

Question
QUESTION: I have a 1963 MGM roadster, that has a dual oil and temp. Gauge. The oil side works but the water does not. Bought a new one , installed it but have the same problem. The installation is rather straight forward, can't see where I'm doing it wrong. I think I may have gotten a bad gauge. What do you think?

ANSWER: Hi Billy.  The early MGB water temperature gauge is purely mechanical.  To test the gauge, place the sensor bulb in a pan of boiling water.  The needle should rise quickly to the HOT position.  If the gauge stays on COLD, then it is faulty.  Do not heat the sensor with a naked flame, because the gauge can be damaged if the needle is forced beyond the HOT position.

Please note that the long thin tube between the gauge and the sensor is very fragile.  It is filled with Ether liquid.  If you kink it or damage it when installing the gauge, you can easily split the tube.  All the Ether will then evaporate leaving you with a non-functional gauge.   



---------- FOLLOW-UP ----------

QUESTION: Mr. Jones have purchased a new dual gauge, did the boiling water test and the gauge works. But once installed we have the same problem. We removed it again and did the hot water test and it worked. Now what?

Answer
Hi Billy.  Once you have installed the new gauge, fill the radiator with water plus antifreeze, remembering to turn the heater control to HOT in case you get an air lock.  Now start the engine and watch the gauge while the engine warms up.  You should be able to see the gauge gradually coming up to the normal position.  Let me know what you observe.