Hello
If it isn't one thing, its another. While fighting to get my Carter W-1 working properly I have another issue that won't go away. The prior owner ran the the heater hose to the top of the block as well as placed the shutoff valve there too. I was told that it was incorrect so I moved the newly purchased shutoff valve and heater hoses to the water pump area.
-The problem: coolant keeps leaking from the fitting despite using teflon to seal any possible leaks. I purchased a new fitting to the block from chevsof40s or Filling station(i buy form both to support them). I found the original fitting I didnt know i had and wonder if the mating between the original fitting and the probe nut will fit better than the reproduction? Am i just doing something simply wrong?
-Attached images are one of a similar probe that has the probe nut and shaved sides like mine(not sure why they are shaved) and my installation
Thank you
Michael
38 Master sedan

There are actually 3 places where that connection can leak. The key is to determine which one is leaking.

it can leak where the larger fitting threads into the block. Possibly the shut-off valve and heater connection damaged the threads in the head. You might try chasing them with a pipe thread tap.

It can leak where the probe nut fits into the fitting in the block.

The third area is where the capillary probe seats into the fitting in the block. If that fitting does not have clean and smooth seat for the flange on the probe it will leak.

Unfortunately there is a possibility that the fitting you purchased was not made properly. I see the word "China" on the fitting.

Have you tried reinstalling your original adapter fitting?

Mike

Thanks gents, it is leaking between the probe nut and adapter. I will install the original adapter which I would have done if I knew I had it but didn’t find it until I put everything together. That China label bugged me when I saw it too.

It is probably leaking between the temp probe and the adapter. Three years ago after an engine rebuild mine leaked there. No amount of torque would stop it. I finally made a small, thin paper gasket, put it between the probe and the block fitting, tightened the probe fitting snug. No leak and its still going.

Plain old pipe dope will serve you way better than Teflon tape for stopping/preventing leaks. It also serves as a light duty thread lock.

I have used an o ring on the sensor bulb pushed up to what remains of the flange on the bulb. Used a 2or 3mm size from one of those multiple choice selection boxes. I only tighten enough to stop the leak.