MTFCA Forum

I just got a new Radiator from Bergs. I attempted to install a petcock i got from Snyders long ago and it will not fit.
I do not know if I should tap the radiator or try a different petcock. Snyders number A-8115-RE. It looks like a 3/8-24, but I am wondering if it is tapered toward the top. Thank you for your help.

David, that petcock is the same as those used on the pan for checking the oil levels. It is a tapered thread. The A prefix on the Snyders part usually denotes an A model part. I do not know if the petcocks are the same.

Allan from down under.

Should be 1/8" NPT, pipe thread. That is what is needed. Check that new one or use another correct petcock.

The only drain on the A is the radiator and it would be the same as T.

Snyder's descriptions for the A-8115-RE says "This petcock is used for model A and model T. Model A used it in the water return pipe. Model T's used it for the radiator, oil pan, and fuel sediment bowl. 1/8" NPT. U.S.A" I'd take what you got to the local Hardware Store and size it - could be that you got something by mistake.

Or maybe they didn't tap the hole in the tank deep enough, wouldn't be hard to tell by trying a 1/8" pipe tap in it. Dave

When you use an NPT tap, I assume there is a way to do it other than just like using a regular tap. Do you just turn to a certain depth and stop? Since it is tapered, how do you know how far to go?

It's like tightening bolts (turn them until just before they break). Tap only deep enough to make the threads.

Don't hold me to this, but I've been told that you stop tapping when there are 5 threads left on the tap above the hole.

I always just run the tap in a bit and then try the fitting, repeat as needed. That way, a fitting that may have had the threads chased in the past and is on the small side will still tighten up nicely. Also, fittings, as with most things, have a +or- tolerance which can lead problems if the wrong ones are matched up and you need a fitting to line up in a certain place. Dave

I also have a Berg's radiator, and the original petcock fit perfectly. Unless Berg's didn't tap the hole properly, I would take a close look at the petcock. Once you modify that radiator, Berg's is off the hook for any other problems, so I would be absolutely positive of what the issue is prior to doing anything. Before I grabbed a tap I would call Bergs and explain the issue and see what he recommends.

Whatever you do, when all is resolved, make damn sure the petcock is tightly seated in the outlet !! Usually they're a bugger to get out if you need to remove one. I never thought about mine, presumably it had been in place long before Lizzie adopted me, but one time last summer, I took Lizzie down to the hay field to check the wheel line; I almost took a joy ride around the section, then decided not to. That was fortunate, as the petcock fell out somewhere in that half-mile loop, and Lizzie was mighty hot under the collar when I pulled in the yard - not a drop of water in the system ! Thank heavens, no harm done.

On the left is the OR (original) petcock and on the right is the RE (reproduction) petcock.

The original petcock would turn about 2 1/2 times and the reproduction would only turn about 1 1/2 times. I applied Megaloc thread sealant and installed the petcock. I then used a crescent wrench to tighten it some more. It definitely will not come out and i doubt that it will leak.

Thanks to all for their input.

David, that non original petcock looks to have a slotted head screw to hold the turning piece in place. That is the problem with the early original style petcocks. If that screw comes loose, the petcock can/will open and there goes the fluid. When this happened on my 1912 van, I wired it shut; ugly but effective. I have since jetisoned the original, correct petcock for the more reliable later style.The washer, spring and split pin are reliable mechanical components.

Allan from down under.