Just had my Northstar engine resealed. Started to get an oil leak and it got progressively worse over time. Very reputable garage here locally and they did a superb job. Every seal/gasket replaced along with hoses, oil cooler lines, oil filter, and oil pressure sensor. My GXP only has 71k miles and she runs terrific now. Best of all, the garage guaranteed their work for 5 years/50k miles. It was expensive, but I plan on keeping the car so it's worth it to me.

Had mine done last week. Purchased the car last month knowing it had a lower crankcase leak. Car is in excellent shape otherwise. Crimson red tintcoat/dark pewter interior with every option except heated seats. Was in sellers family since 05 and said was always garaged and driven in rain only a handful of times and it shows. Car is near showroom inside and out with every service record dating back to when it was originally sold, which is the only reason I purchased knowing the needed work required. Ended up getting a complete seal of all gaskets, new oil manifold, bearing studs, oil cooler hoses, new crankshaft position sensor and valve covers/gaskets. Performed locally at shop owned by former Cadillac service manager. Did a great job. Out of curiosity, how many hours did yours bill out at? Mine was 25hrs at a total cost, including tax, right at $2500.

Paid almost 4k..had to replace the power steering lines also.

Unless they did AN fittings on the cooler lines, they're probably already leaking again. If not, they will be soon. It's just the design of the fittings on the OEM lines.

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Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck