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Oil Cooler o-ring size 1999 Chevy Express 2500 5.7

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Anyone know the size of the o-ring that goes inside the fitting that screws into the radiator for the oil cooler?  Mine is leaking bad.  I replaced the radiator years ago and can't match this fitting with anything on the internet or local auto shops.  I thought I got a basic radiator from NAPA years ago but even they have no clue on these fittings (NAPA guy mic'd the threads and said 22mm).  Last time this happened I just replaced the o-rings but I've lost that info through the years and can't find it anywhere.  I've already picked the old o-rings out (was hard as a rock on the top one so broke into pieces) so I'm without my work van until I can get o-rings.  Thanks for any help.

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Quick disconnect fittings?   Why not buy new fittings? That or buy an o-ring assortment box and find one that fits.


The only time I had an issue I just replaced the fitting since it was only $4 or so

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Txab that was my plan to just buy the fittings and be done with it but noone had the correct one including extensive internet searches.  I went to Lowe's and got a box of #10 o-rings.  The last time I did it the fix has lasted a few years so I'll see how this does.  It was just a pain to find the correct o-ring to fit in the fitting.  Once I got to Lowe's and was looking at the boxes of o-rings it started to come back to me which ones I bought last time.

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