pipe thread sealer

[67hat34c]

I took off the exhaust manifold on my onan mcck. machined it and bead blasted and painted it. now the nipple that screws into the elbow and the exhaust manifold will not fit properly. When i tighten it into the exhaust manifold the proper down angle position for the elbow will not allow the threads to tighten properly i can wrench it around 3/4 of the way but can make it far enough. is there something i can use on the threads? or do i need to go back to the machine shop and have them cut the pipe thread a little deeper. All they did was clean the thread before.

When I took the elbow off it had some type of heavy guage tape on it way thicker than teflon tape.

 

[Nonchalant1]

Leave the pretty manifold alone and just chase the threads on the nipple, but do it in steps. Chase the threads, try it, chase the threads, try it. You can always go a little farther, but you can't put any metal back on.

I'd use Fuchs 762 Hi-Temp sealing compound when you reassemble it.

Doug Shuman

 

[yachtsmanbill]

ONAN had several recalls / warnings about those nipples cracking and letting carbon monoxide get into the boat. Its on the dry part of the exhaust. I changed mine and put a Sch. 80 SS nipple in its place. USE PIPE DOPE instead of tape !! A new one will tighten into position; never loosen them to adjust, especially THAT one. AND never use it for a step ! ws

 

[67hat34c]

nipple is SS, Will take it back to machine shop and have them chase it. Dont have a 1.25" tap.

 

[yachtsmanbill]

try flipping it end for end. put both fittings together and tighten the water el first until its in position. theyll all be tight then. ws