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Proper "feel" when tightening o-ring connections

brimac50 on Fri August 30, 2013 6:46 AM User is offline

Year: 1980
Make: Chev
Model: C20

This is could be an generic question, I suppose. My concern is having the correct o-ring, for a particular fitting connection. I'm not a regular, at this type of work, so I don't have a lot of experience to pull on.

When tightening down a fitting connection, with a new o-ring, .... should the collar of the male fitting, ever "butt up" against the female fitting? Or, should the compressed o-ring always separate the two? I have a few connections where, there isn't much o-ring resistance, when tightening, and end up metal to metal, as described. On those I'm assuming they'd leak. With the connections I'm not worried about, you can feel the resistance of the o-ring when tightening. And, the female fittings have not butted up against the male collar. From my limited experience, I'd say that is correct. The only OEM parts left on this system are the "through the radiator support" tubing to the condenser. Everything else is a replacement. I know that might be a possible factor. Any thoughts? I'll check with NAPA later today, for "proper" seals

GM Tech on Fri August 30, 2013 8:53 AM User is offline

O-rings seal ID to OD.... they are not compression gaskets! so the connector is there just to hold the joint together-- more torque means nothing-if the joint leaks, you have the wrong sized o-ring or junk in the sealing area or a bad sealing surface--

sealing washers however use a gasket seal approach- more torque does mean more compression- but these have manifolds that flaten out the sealing washers- not tubular threaded joints..

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Fri August 30, 2013 10:55 AM User is offline

What GM Tech said. Tube joints should go all the way together since the o-ring seals on the sides. The nut does not have to be very tight at all.

NickD on Fri August 30, 2013 7:40 PM User is offline

Corrosion on an O'ring fitting will cause a leak, where on a flared fitting, can even stop a leak. So why are they using O-rings, guess they want these fittings to leak.

And since that O'ring is a media between two pieces of metal, that metal should have a mirror finish or else it will leak. If badly corroded and cannot be polished, has to be replaced. Also have to be darn careful that ring is not twisted when installed. With a flared fitting, a tad more muscle will cure that.



Helps greatly with O-rings.

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