Oil and water gauge replacement

Hi ,I have a non functioning water temp gauge, seems to be the mechanical side of things in the instrument, hand will not move on the water gauge side of things, I have tested it by applying heat to the bulb end and no movement, ( don’t ask how it got broken!) anyway I have seen that there are smiths oil and water replacement units available, but I am not sure how I would go about transmitting the water temp from the existing arrangement to the new gauge, has anybody made this modification and if so what is required
thanks for the help

The meter end can be sticky. Mine tended to stick and I squirted a little mist of release oil into it and that sorted it.


Hi Pete I think its more than that, I can’t get the needle to move if I try to lift off its stop, looks like Mechanical issue inside the gage

Mine would stick at the end stop and it either wouldn’t move or if the temperature was high enough it would jump but not all the way but might take a few more jumps before reading correctly. Tapping it might help but try using an aerosol of release oil squirting into the back of the gauge.


If the diethelether has leaked out of the bulb in the sender no amount of tapping or spraying anything will move it.

If the needle sticks to the pin but eventually releases with a jump, the problem is the stop pin. The pins have a thin coating, or probably a tube, of rubbery material. When this ages, it becomes sticky like perishing rubber. I believe its purpose is simply cosmetic - black sleeve for a black dial. You can scrape it off and leave it as a silvery metal or replace it with paint or put a new sleeve on. I found suitable tubing material from the leads used for ear buds. Just remove the copper wires.

That’s not your problem Mike. If it has jammed and the needle won’t move, the mechanical parts inside have wedged somehow. If you have not opened one of these Bourdon tube mechanical instruments before, they are very simple. The tube is curved and when it is pressurised, it tries to straighten. The outer end of the tube has a link arm which pulls on a sector gear. The teeth on the gear engage with the teeth on the needle spindle. My guess is the sector gear is seized somehow and it should be able to be reset if nothing is broken. To inspect, twist the bezel off, remove the glass, then remove the couple of screws in the housing. You should be able to ease the mechanism out complete with the dial. Don’t break or cut the capillary tube as you will need it refilled with ether and reconnected.

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Here it is with the oil pressure mechanism removed.

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On the statement about the bulb being “don’t ask how it got broken”, please know that if the ether inside the bulb and associated pipe has leaked out then the meter needle will not move no matter how much heat is applied to the bulb. A filled and sealed ether system is required for the unit to work. Otherwise, an entirely different sender and temperature gauge would be required.

Hi Mike,

You have innumerable instrument restorers in the UK (lucky people). I found at least 10 on a quick ‘web’ search. Others will know who is reliable and represents value for GBP. I found this one at the top of the list https://melvyn-rutter.co.uk/restoration/instruments/ by way of example. It is far better to keep the original instruments rather than try to replace them.


Hi and thanks all for the advice

The tube has not been damaged, the quote don’t ask how it got stuck is because I removed the outer face of the dial to repaint it whereby the needle for the water temp fell off, after cursing myself I then removed the three locking screws that hold both units in the gauge and thought I could remove the barrel of the gauge to get to the workings, I replaced the needle and got both the securing screws back in to hold both the gauges, however, the water gauge needle jammed every time I positioned it to tighten the screws up, I was afraid of damaging things if I played around with the internals, however Pete’s description of how they work has given me confidence to release it from the barrel and try to reset it, this is not easy though whilst still in the car, I will give it another go before the weekend and post if successful