The Northstar engine is a family of GM engines produced from 1993 until 2011. Considered a very technically advanced engine, the Northstar is a traditional 90-degree V8, double overhead cam, with four valves per cylinder. While it initially debuted as a 4.6L V8, the Northstar engine had numerous variants including a 4.0L V8 and a supercharged 4.4L V8. A 3.5L V6 version was produced under the LX5 engine code, also dubbed the Shortstar.
As the first production GM V8 with overhead cams, the engine was technologically ahead of its time for production V8 engines. As such, it won the Ward’s 10 Best Engines three years in a row from 1995-1997. However, despite its successes the engine suffers from a number of common engine problems that are detrimental to the Northstar engine’s reliability.
Northstar Engine Applications
Since the Northstar came in a bunch of different variants and vehicles, we’ll lay out which cars had which engines. Additionally, we’ll do our best to specify which variants are most prone to the common problems we mention below.
L37: 4.6L V8
L37 models have VINs that begin with 9.
- 1993 Cadillac Allante
- 1993-2002 Cadillac Eldorado
- 1993-2004 Cadillac Seville
- 1996-2005 Cadillac DeVille
- 2006-2011 Cadillac DTS
- 2008-2011 Buick Lucerne
LD8: 4.6L V8
LD8 models have VINs that begin with Y. It has a lower redline and was designed to produce more torque than the L37 models. Since it is predominantly used in the same vehicles you will need to check the VIN number to determine which Northstar variant you have.
- 1994-2002 Cadillac Eldorado
- 1993-2004 Cadillac Seville
- 1994-2005 Cadillac DeVille
- 2006-2011 Cadillac DTS
- 2004-2005 Pontiac Bonneville
- 2006-2007 Buick Lucerne
LH2: 4.6L V8
Also a 4.2 V8, the LH2 is a modified Northstar meant for rear-wheel and all-wheel drive vehicles. Additionally, it added variable valve timing which increased horsepower to 320hp.
- 2004-2009 Cadillac SRX
- 2004-2009 Cadillac XLR
- 2005-2010 Cadillac STS
LC3: 4.4L Supercharged V8
The LC3 reduced the engine size for improved strength and to minimize head gasket leaks. It includes a supercharger and variable valve timing and produced up to 469hp and 439lb-ft. of torque. It was exclusively used in high end performance Cadillac’s, although short-lived due to poor sales.
- 2006-2009 Cadillac STS-V
- 2006-2009 Cadillac XLR-V
L47: 4.0L V8
- 1995-2003 Oldsmobile Aurora
- 1999-2005 Shelby Series 1
LX5 Shortstar: 3.5L V6
- 1999-2002 Oldsmobile Intrigue
- 2001-2002 Oldsmobile Aurora
Northstar Engine Problems
- Blown Head Gasket
- Rear Main Seal Oil Leaks
- Valve Cover Oil Leaks
- Excessive Oil Consumption
- Carbon Buildup
Despite its 18-year running history, the Northstar engine is susceptible to a lot of problems. The design of the engine is the predominant cause for the majority of these issues. While some have been remedied over the years others are still common even on newer Northstar vehicles.
While these problems might mostly appear to be minor the biggest problem with the Northstar is the cost of repairs. Due to its transverse design and engineering it is a rather expensive engine to repair when problems do arise.
1. Northstar Blown Head Gasket
Head gaskets hold an air-tight seal between the head and the engine block. They are crucial for maintaining cylinder compression and preventing oil and coolant from leaking into the combustion chamber. Operating between the block and head, the head gasket is subject to high temperatures and lots of pressure.
Head gasket failure is common for all Northstar engines. The engines head used torque-to-yield bolts, also known as TTY bolts. These are one-time bolts meaning they need to be replaced every time they are removed. Once TTY bolts are tightened they stretch. When the engine overheats the bolts stretch even further and don’t contract after cooling down like most metal does. When the bolts remain stretched and the head contracts, the head becomes loose on the block which causes the head gasket to blow.
While the Northstar engine was actually designed to be difficult to overheat, design flaws actually made it easy to overheat. As we’ll discuss further on, these engines burn a lot of oil which creates a lot of carbon buildup. This carbon buildup then causes increased engine temps which can blow the gasket too.
Lastly, the head gasket can also fail if the head bolts are removed and reused instead of being replaced.
Bad Head Gasket Symptoms
- Rough idling
- Poor performance
- Lack of acceleration
- Milky white residue in oil
- White smoke coming from exhaust
- Bubbling radiator and coolant reservoir
Unfortunately, with the Northstar head gasket sealer and other tricks don’t work. The only way to repair the gasket is to replace it along with the TTY bolts. The best way to prevent this from happening is to prevent the engine from overheating. Turn it off immediately if it ever gets above normal operating temps. And make sure it is always topped off with coolant.
2. Northstar Rear Main Seal Oil Leaks
Northstar engines produced through 1999 commonly develop oil leaks at the rear main seal. The rear main seal is located at the back of the block where the the crankshaft exits the block. It’s responsible for preventing oil from leaking at the crankshaft exit.
While most rear main seals are pressed into the block, pre-2000 Northstar’s didn’t use pressed seals. This leads to the seal wearing down faster from the crankshaft spinning. Additionally, low engine oil levels or infrequent oil changes can also cause the seal to wear down and leak more frequently. Lastly, not driving your car for prolonged periods of time can cause the seal to dry out and crack causing it to leak.
In 2000 Cadillac redesigned the rear main seal by pressing it into the block which solved the premature wear issues.
Cadillac Rear Main Seal Leak Symptoms
- Low engine oil
- Oil dripping from back of the block
Fortunately, a rear main seal leak isn’t the worst thing in the world. Generally it will usually just cause a small leak from the back of the block or crankshaft. The biggest potential danger is this oil leak causing your engine oil to run low which can then cause catastrophic internal engine damage.
Unfortunately, diagnosing a seal leak is difficult due to its engine location. Before paying to replace the seal we recommend trying to use some sealer, such as BlueDevil Rear Main Sealer.
3. Northstar Valve Cover Oil Leaks
A valve cover sits on the top portion of the cylinder head and prevents oil from leaking as it lubricates the camshafts, valves, etc. Similar to the cylinder head, the valve cover is also sealed with a gasket that sits between the cover and the top of the head. Northstar overheating can lead to cracked valve covers or bad valve cover gaskets.
When the valve cover fails it is usually the cause of small hairline cracks within the cover. When these cracks form they let pressure and oil out and eventually increase in size causing more leakage. The gasket is also prone to failing from heat, but is also a common maintenance item. Gaskets go bad over time from normal wear and tear and as these engines get older the gaskets are more likely to fail.
Northstar Valve Cover Gasket Failure Symptoms
- Oil leaking around the cover
- Burning oil smell
- Low oil levels
- Rough idling
- Cylinder misfires
Valve cover leaks can vary in degree. Usually they start small and then expand and worsen over time. The smell of burning oil through the air conditioning vents is a tell tale sign. As the leak progresses you will begin to notice low oil levels and possible misfires and poor idling.
Unfortunately the only options here are to replace the cover or gasket. Whichever it is that needs replacing, it’s not easy. The valve cover is connected to various other engine components which requires a lot of things to be disassembled for it to be removed.
4. Excessive Oil Consumption
Northstar engines are known to consume copious amounts of oil. While this is normal for a lot of high-performance V8’s it is mostly caused by the engine design. Northstar engines are known to consume up to 1 quart of oil every 500-1,000 miles. This is most common in 1993-1999 engines as the piston ring design was changed in 2000.
The oil consumption can be caused by leaks, but in this instance it is being burned off in the combustion chamber. The piston ring grooves are prone to carbon buildup, as discussed below. When this happens the rings get stuck in the ring lands and can’t clean the cylinder walls. This then causes blow-by to seep into the crankcase and oil to burn in the cylinder walls.
The result of blow-by getting into the crankcase is poor performance and bad fuel economy. What happens is this blow-by then gets recirculated into the combustion chamber through the PCV valve. This reduces the amount of oxygen in the combustion chamber which can cause misfires, rough idling, and overall poor performance.
Fortunately, this issue is remedied through cleaning the piston rings.
Northstar Piston Ring Cleaning
The excessive oil consumption is less of the issue here; the result of the excess carbon buildup in the piston rings is the issue. Since GM can’t solve the piston ring design issue the best remedy is to clean the piston rings.
The ring cleaning process includes filling the cylinders with a cleaning solvent, or seafoam, which dissolves the carbon and cleans the rings. The solvent is injected into the cylinders via the spark plug holes.
While cleaning the rings will fix the performance issues it won’t fix the underlying issues. This means cleaning the rings will need to be done again when the symptoms arise again.
5. Northstar Carbon Buildup
We’ve talked a lot about carbon buildup and how it can cause a myriad of problems like head gasket failure and poor performance. While pre-2000 engines faced a carbon buildup issue that was caused by the piston rings, another carbon buildup issue arose for 2000-2002 engines.
These engines commonly buildup carbon within the cylinders. These carbon deposits are heated up during combustion which creates further heat within the cylinder, burning oil and causing the engine to knock or ping under acceleration.
This problem mostly occurs in early 2000’s models and can be fixed by using seafoam and some fuel system cleaner.
Northstar Engine Reliability
Are Northstar engines reliable? Yes and no. The technical advancements this engine made also led to a lot of problems that were created by poor engine design. When the Northstar is reliable it’s a great engine, when it’s not it’s a terribly painful engine to own.
While most of the problems we mentioned sound relatively easy to fix, they aren’t. The engine design makes a lot of what would be simple repairs into labor intensive and expensive repairs. Therefore, the biggest problem with the Northstar in my opinion is the cost of maintenance and repair.
Temperamental is the best way to describe this engine. While the service manual calls for 7,500 to 10,000 mile oil change intervals, don’t listen to it. Keeping the Northstar reliable requires proactive and tentative maintenance. Change the oil every 5,000 miles. Make sure it is always topped off on coolant. Always run high-quality synthetic oil and put a bottle of fuel cleaner in the gas tank every few fill-ups to help improve reliability.