Cadillac Northstar Engine Problems

History

The Northstar debuted on the ill-fated Cadillac Allanté, a two-seater roadster that Cadillac hoped would compete head to head with the sports car line-up coming from Germany and Japan. The Allanté was an epic failure, but the Northstar survived for nearly 20 years until GM announced it was retiring the venerable engine in 2010. Most Northstar versions displaced 4.6 liters and could generate up to 300 horsepower. A 4.4-liter version produced from 2006 to 2009 generated up to 469 horsepower in the Cadillac XLR-V and STS-V. A four-liter version powered some Oldsmobiles, according to Autotropolis.com and Allanteatlanta.com.

Precisely because the Northstar was a high-performance engine, in many ways it behaved like a delicate flower. It was an engine much like the high-performance Mercedes-Benz S-Class and Italian-made roadster motors. It could be temperamental with special needs. The Northstar featured a die-cast aluminum block. The bottom end girdle bisected the bottom of the engine along the center of the crankshaft bearings. There were no main bearing caps found on other engines. However, the engine was prone to oil leaks because aluminum was porous. GM in 2000 developed a new process that "squeezed" the lower crankcase casting to reduce leaks.

In the 1990s, the Northstar V-8 had four primary problems: head gasket failure, oil leaks, high oil usage and oil burning. Cadillac enthusiasts generally dismissed high oil use as a problem, noting that it's not uncommon for high-performance engines to use a large amount of oil. GM noted that one quart of oil per 1,000 miles was not unusual since 32-valve tubes must be adequately lubricated. What's not normal was the buildup of carbon in the rings that also led to high oil use. A GM-made cleaning kit usually solved the problem.

Common among the 1996 to 1999 Northstar V-8s were oil leaks originating at the rear main crank seal. Part of the problem was due to the aluminum block but also the seating of the oil seal in the block. GM solved the problem by developing a rear main oil seal that pressed into the block. It could only be removed and replaced by a special GM service tool.

Head gasket problems also plagued the Northstar. Burning oil and the resulting buildup of debris in the engine caused it to overheat and blow a gasket. In other instances, the heads may have been serviced or replaced and then re-installed with a new head gasket using the original head bolts. The threads of the original head bolts were weakened after removal and no longer secured the head and gasket properly. New head bolts were required. Replacing the head bolts out of sequence and at the wrong torque values could also lead to a blown head gasket.