Radiator Drain

[Barrman]

Since it gets below freezing for maybe 5 nights a year around here. A large number of people don't run anti-freeze in vehicles once they have to do coolant system repairs. When those cold nights come, they just drain the system or hope nothing freezes up.

That must be what the previous owners of all the M715's Sermis and Pistolnut own. Because all the radiator drain plugs are missing. No problem, I will just buy a new one so we can finish up the small block conversion for Pistolnut I think. I buy a 1/8" NPT drain and it won't fit. Real close, but no fit. Maybe the threads are messed up I think and run a tap through the radiator side. Still no fit. I take the part back to the parts store and they laugh at me when I ask for something just a hair smaller saying nothing is smaller. So, I run the plug through a 1/8" NPT die. Still won't fit.

My stock radiator is long gone as well, along with the plug. Can anybody tell me what size the drain is supposed to be and why it is different from what auto parts stores are selling these days?

Thanks.

[randyscycle]

Could the plug be 1/8" BSP? A British thread? If you have a thread gauge laying around see how many TPI it is. I've run into that a few times. There is also a metric pipe plug that is close to the 1/8" pipe thread as well. I think I have a few of those taps around here somewhere.

[Mikel]

Antifreeze also lubricates the water pump seal and prevents corrossion. It also raises the boiling point of water. Worth using for any of those reasons.

[Barrman]

I agree about the coolant being a good thing. I was just reporting why out of 4 M715's there is not a single stock radiator drain that came with the trucks.

[porkchop]

Tim, I can send you a plug. I have a spare radiator in the garage that has the plug in it. You can then use it to acquire one for the rest. I wouldn't need it back since I can just transfer the one from this radiator to the next if I should have to replace my radiator. Plus I don't think I will be going with a stock radiator if I have to replace mine. Just PM your address to me again.

[brute4c]

Figure out what thread it is, please post...seems like another hole in our knowledge base...