Ken,
I checked Parts Book 78Z / Section 8 - Engine / Page 8-11 / 8.009 - FILTER - OIL and found P/N 643950 GASKET which I believe to be
between the oil filter base and oil filter adapter. Unfortunately there is no drawing so I couldn't tell if it was a square gasket
or a round o-ring. I checked other parts of the manual and noted that it uses "RING - "O" so P/N 643950 could in fact be the same
square gasket that is used in the oil filter. In the maintenance manual there is a line drawing and it sure looks like a square
gasket and not an o-ring:
http://www.gmcmhphotos.com/photos/455-2f-403-engine-oil-flow-path/p58336-oil-filter-base-cooler-adapter-26amp-3b-filter.html
Having noted all the above based on my experience working with pneumatic and hydraulic systems I did not like using a seal in the
oil cooler adapter that completely filled the o-ring groove and stood proud of that groove.
Someone else had mentioned that they had success with the Dorman kit P/N 317-916 so I bought one from O'Reilly's. It is not an
o-ring either it has a rectangular cross section, however, it does not fill the groove completely. When I installed it I noticed
that I had to stretch it to get it over the ID of the oil cooler adapter ID. After torquing the extension that attaches the oil
cooler adapter to the oil filter base to 55 ft lb the oil filter base and oil filter adapter were a metal to metal fit and it did
not leak.
However, being a pedantic bugger I didn't like the fact that you had to stretch to install it I decided to contact Parker Hannifin
engineering. I gave them the dimensions of the groove and they came up with P/N PH 2-230.
When I installed that seal and torqued the extension to 55 ft lb once again I got a metal to metal fit and no leakage.
Conclusion: GMC probably did use the square gasket out of the oil filter between the oil filter base and oil cooler adapter.
However, over time it is likely to cold flow, loose torque, and leak. If you do use a gasket from a used oil filter I would suggest
cleaning all the oil off of it and the interfacing surfaces and installing it bone dry. That will help keep it from cold flowing.
IMO the best thing to do is to use the Parker Hannifin O-ring 2-230 followed by the Dorman 317-036.
Here's another example of an oil filter gasket that cold flowed and leaked:
http://www.gmcmhphotos.com/photos/emergency-oil-cooler-line-repairs/p11683.html
Interesting information from John H. which kinda contradicts what I've noted above and is fine with me!
http://www.gmcmhphotos.com/photos/g6408-oil-filter-and-cooler.html
I reckon this horse has been flogged to DEATH!
Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Ken Burton
Sent: Saturday, June 24, 2017 11:53 PM
To: gmclist
Subject: Re: [GMCnet] Oil cooler adapter at block
Chris,
I used the recommended ring off of a Fram oil filter and tightened it to the spec. (I believe it is 55 Ft Lbs.) It will crush over
time, so the next three oil changes I checked it again. On the first two it did require some additional tightening. On the 3rd it
was just fine. I replaced it a least 12 years ago and have not needed to replace it again.
If it bothers you, replace it once and simply check that the thing is still tight during your next few oil changes.
I might replace it again in the next 5 years or so since it is easy to do.
--
Ken
