Re: [MV] MV] M54 injection lines leaking, need help

From: DDoyle9570@aol.com
Date: Wed Apr 30 2003 - 05:42:54 PDT


In a message dated 4/30/2003 2:31:01 AM Eastern Standard Time, stalwart@nwlink.com writes:

> Can't give you a torque spec,

I can, its 23-25 pound-feet.

Remember, this is not pipe thread. Actually, what we call pipe thread is a tapered thread known as NPT. I have never researched this, but with the military's mentallity for minimizing supply items, I suspect most of the "pipe thread" connections on our vehicles a NPTF....now commonly referred to as a "dry-seal" thread, actually National Pipe Thread for Fuel. The fittings will interchange between NPT and NPTF, but NPTF was intended for fuel and other systems where the use of sealing compounds, especially tape, should be avoided.

The tapered pipe threads seal there connections by squeezing the metal together. In certain other tipes of connections, like those of the injector lines, the threads are only mechanical connections, to guide and physically hold in place the line, the sealing surface is achieved by close tolerence, precise fit parts. The liquid should not, by design, ever contact any part of the threaded surface. When there is a leak in this type joint, continued tightening rarely results in an improvement. So long as the mating surfaces were clean and blemish free, and the connection was properly torqued to begin with, it should be leak-free.

My .02,
David Doyle



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