Re: Temperature Gauge 1939 120
Posted by HH56 On 2018/3/2 16:04:39
The bulb and tube has to fit thru the hole in the instrument cluster mounting plate so bulb must be removed from the head and the entire length of tubing and bulb pulled into the passenger compt and thru the mounting plate before the gauge can be separated and taken away for repair.
Your instincts for caution are spot on. The nut is not fixed to the tube and bulb so with a bit of penetrating fluid and a lot of patience and care it will come free and spin while the tube and bulb is stationary. The issue is the bulb could be surrounded by sediment and effectively cemented into the head. If it has never been removed since new almost guaranteed. I don't believe anyone has found a surefire way to dissolve the sediment or calcium or whatever to free the bulb reliably and that is where the problem arises. I believe some of the sediment removal products and acid etches have been tried with varying to no success. There is no place to grab and remove the bulb other than pulling the tube so tube is frequently pulled or twisted off while the bulb stays put.
Some have managed to install a tee in the heater water out port on the head for a temp sensor but the downside there is if the heater is shut off there is no water flow so all you have is conduction and are not able to get an accurate reading.
There are some metal hose adapters that will tee into the upper radiator hose that are made for modern cars needing extra sensors. I have looked but so far haven't found one large enough for the Packard hose diameter. I did a variation on that approach by making an adapter out of 1" aluminum to fit under the thermostat housing. It will sense accurate water temp as flow goes thru but until the thermostat opens and water can flow past the sensor it lags a bit.
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Your instincts for caution are spot on. The nut is not fixed to the tube and bulb so with a bit of penetrating fluid and a lot of patience and care it will come free and spin while the tube and bulb is stationary. The issue is the bulb could be surrounded by sediment and effectively cemented into the head. If it has never been removed since new almost guaranteed. I don't believe anyone has found a surefire way to dissolve the sediment or calcium or whatever to free the bulb reliably and that is where the problem arises. I believe some of the sediment removal products and acid etches have been tried with varying to no success. There is no place to grab and remove the bulb other than pulling the tube so tube is frequently pulled or twisted off while the bulb stays put.
Some have managed to install a tee in the heater water out port on the head for a temp sensor but the downside there is if the heater is shut off there is no water flow so all you have is conduction and are not able to get an accurate reading.
There are some metal hose adapters that will tee into the upper radiator hose that are made for modern cars needing extra sensors. I have looked but so far haven't found one large enough for the Packard hose diameter. I did a variation on that approach by making an adapter out of 1" aluminum to fit under the thermostat housing. It will sense accurate water temp as flow goes thru but until the thermostat opens and water can flow past the sensor it lags a bit.
Attach file:
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(107.14 KB)
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