Originally Posted by Alaska_Man
My brother has a 94 GMC Yukon with a stock 350 in it. It has 2 tapings, right next to the oil filter, that go up front to the radiator. We think they are just for cooling the oil. These lines are leaking and as we live in Alaska, we don't think we really need an oil cooler and we're thinking of just plugging the outlets, on the block, and doing away with lines. Would that be OK? Just wondering if, by plugging the outlets on the block, if pressure would build up there and do some damage to the engine?
They are for heating the oil. Everywhere they are part of the emissions reduction system intended to get the engine warmed up faster. It has the side benefit of significantly reducing piston, ring, and bore wear as the cold start rich mixture comes off a lot sooner reducing the fuel wash of the upper cylinder lube.
In Canada and Alaska these oil warming systems were used for many years to overcome the cold weather start issues of excessive wear from long periods of rich start operation long before they were put on lower 48 vehicles as an emission reduction measure. Your TBI truck has this feature it's managed by software instead of a choke as on carburated engines, but the cold rich running (choke) feature is still there just done differently. The computer does not shut this off till the coolant reaches 176 degrees F.
The fittings you're talking about can be removed from the adapter and radiator to be replaced with conventional fittings. You can do this with 1/4 or 3/8s (I forgot which from the last time I did this) male NPT to 1/2 female inverted flare. This should be regular parts store or hardware store stuff, you'll need 4 to cover the adapter and the radiator positions. The tubes can be formed using 1/2 aluminum, a double flare would be nice but a single will work. Or you can get 1/2 pipe to male nipple fittings and use 1/2 high pressure fuel line as sold for TPI type injection systems and make it all out of rubber instead of aluminum. Or 1/2 inch steel brake/fuel line will work. The effort of preserving this system while a PIA to do pays back in very extended engine life, especially where it's so damn cold so much of the time.