There are 2 other possible problematic areas that I am aware of. First one is rear cover gasket. It's on the back side(trans end) of the block, and can leak independently of the rear main seal. Another one to check is the crank position sensor which is apparently above the starter.
I have an '04 Tahoe with 281k on it and I'm in the same predicament with oil leaks. Needless to say my undercarriage is "rust proofed" with all the oil spray from driving with an oil leak.
In regards to your coolant loss, you may have compromised head gaskets, or the dreaded and all too common Castech cracked head. Castech is the manufacturer of cylinder head castings for GM and they made junk head castings that crack with time. Once cracked, the coolant leaks into the oil and causes lots of problems. Plenty of online reading for Castech heads. For a temporary fix of coolant loss, you may consider Bars Leaks additive. I dropped a bottle in my 04 until I can find a replacement drop in engine, or come up with a plan of action to freshen up my existing 5.3.
I am at the point where I think the only way to take care of the multitude of problems that afflicts high mileage 5.3's is to remove the engine from the vehicle and address everything at once. Anyone found a way to effectively fix all the 5.3 issues without breaking the back and the bank attempting to do it in the Tahoe Suburban Silverado Sierra?
