So I had to pull the heater core tube out of the water pump on my 2000 5.9. What's the best way to reseal it? Just stuff an O-ring in with the tube? Silicone? Take the drugs that the engineers were on while designing it?

 

There is an o-ring on the end of it. On my 96 though, the tube rusted off just below the indent for the o-ring... Fortunately, the local parts store had replacement tubes in the "Help" section. I also had to hog out the hole in the water pump a bit, to get it to insert nicely. The hole was just drilled, no cleanup, so, sharp edges around it. Didn't want to cut the o-ring when I put it in there, so, just knocked the edge down a bit, and worked perfect.

 

What's funny is mine didn't seem to have an o ring. It was just sealed in with dust and atf from the leaking power steering pump. I'll have to double check and make sure the o ring isn't sitting in the bottom still but this design is one of the worst ways they could have done it. XD I asume the water pump is a dinosaur design that wasn't expected to need to deal with a heater core?

 

There is a bit of a 'slot' in the tube for the o-ring, and it can flatten out, so it looks like the tube is just one continuous piece, all the same diameter. Fooled me at first...... Cleaned it up, and discovered what was missing.

 

I went and double checked the tube and there was an o ring in there. Although it was perfectly shaped to just fill the channel with no visible seam... It came out almost like powder. Threw a new one on and its holding. Are the HNBR o-rings as long lasting as the vitons or do you think it would really matter?

 

No clue there. If it doesn't leak, run with it. If it starts leaking, change the o-ring again.