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Hi all, newbie here. Just getting to know my ‘37 Convertible Coupe. Glad to have found this thread. I am fortunate in that my square nut to the head comes off readily. Although the capillary tube is broken I’m interested in trying the repair as found in Skinned Knuckles regarding a ‘33 Plymouth. My question is that beneath the bolt past the threads in the head I’m just finding what appears to be the rest of the head. I anticipated finding a hole to the water gallery wear the bulb sits. Do I have a bulb stuck in the head or does the ‘37 Six use something other than a bulb? Thanks much! Regards, Tad
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Unfortunately you didn't wait for the photos to finish processing so only one was uploaded. You can go back and edit the same posting to add them.

Thanks Packard Don! Photos posted.

G'day gtcoastie,

to PackardInfo.

I invite you to include your '37 Convertible Coupe in PackardInfo's Packard Vehicle Registry.

There should be space in the water passage behind the opening where coolant can freely circulate around the bulb. It it looks or feels like a solid surface after removing the nut the bulb is most likely broken off the tube and stuck in the opening. Calcium and rust can do a job better than some glues and cause the bulb to almost become solid with the head.

Sometime a penetrating fluid or a commercial lime dissolving product continuously applied over a period of time will free it. Other times a rust and cooling system cleaner in the coolant such as oxalic acid will remove enough of the calcium or whatever to free the bulb. Other times it has had to be drilled out.

Most Packards used a bulb with a shoulder and a specific length nut that forces the bulb to seal against a smooth seat in the head. If you use any mechanical means to free the bulb take care not to damage that smooth seating surface or it could be hard to stop any leaks around the nut when things go back together.

Thanks Howard, that makes sense. I'm guessing if I start small and drill in the middle I might find enough to grab to pull the balance of the bulb out. I just didn't want to be blindly drilling into the head unless it was designed to open to the water passage.

Here is what mine looks like for reference.
Yes, the squared fitting bolts into the head, (it is directly into the water jacket space so is surrounded by the coolant), the sensor on the end of the tube (that is broken on yours) plugs into the bore on that fitting (so it is affected by the coolant and able to take its temperature), then the centre fitting that rides on the tube/spring tightens the sensor into the head fitting completing the water tight assembly.
Bob J.

Attach file:

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  Head Fitting.JPG (946.79 KB)


  Sensor.JPG (629.70 KB)


  Assembly.JPG (912.37 KB)

Done...thanks for the link for the Registry.

Bob J, exactly as I anticipated it should look. The only difference is that my square headed nut was directly into the head. Where did you get the spacer or was that part of the bulb/gauge kit? Thx, Tad

for includung your '37 Six Convertible Coupe in the Registry. Notice it's RHD, originally from the UK, I'd love to see a photo of the car.