So, I have a brand new water pump and metal hose section for heater core. What is the best way to seal the threads? Also, if I turn it til tight, it’s not aligned. If I back it off to align, it’s not tight. Should I’d use some Teflon tape?

 

I wasn't 100% sure about the teflon tape so I used thread sealant.

https://www.napaonline.com/en/p/PTX7651155


Also used it for the old temp sensor in the new thermostat housing too.

 

I would agree with Ralph, some sort of liquid thread sealant is best.

 

Damn. Already got it back together with just tape. We’ll see. My sensor only has tape, and it has not leaked at all.

 

Well if it worked well with the sensor.........

 

I'd just use tape. The only time you have to be careful using tape is on a sensor that grounds to the engine (one wire).

 

I always use tape on threaded coolant fittings like this. Probably not the best way but it has always worked for me.

 

I've used tape every time, never had a problem with it.

 

Permatex #2.

 

Tapered threads such as the pipe fitting you're dealing with are designed to be turned past snug to the required orientation. They typically require thread tape or paste to seal properly, by design. Use thread tape/compound on every tapered thread you encounter.

 

I've always used tape with no problems, I did however do a way with the metal pipe and use a 3/8" NPT X 5/8" hose barb

 

Hubba Bubba does the trick, but Juicyfruit will do in a pinch

 

50 miles today. Dry as a bone. Tape seems to be working fine.

 

They're all good options done properly.

 

I have used tape and liquid thread sealant over the years but have started using Rectorseal T plus 2 thread sealant. I had a fitting that just wouldn’t stop weeping and a plumber friend suggested this and it worked the first try…great stuff.