6 Common Cadillac Northstar Engine Problems

The Northstar engine is a family of GM engines produced from 1993 until 2011. From a technology standpoint the engine was extremely advanced and well ahead of its time. This lead it to winning a few “best engine” awards but the use of new technology resulted in quite a few problems and reliability issues. Furthermore, its transverse mounting and unique design make it very expensive to repair. Ultimately, the Northstar is not a very reliable nor is it cost friendly.

In this guide we’re going to discuss some of the most common engine problems that affect the Northstar. These include blown head gaskets, rear main seal leaks, valve cover issues, oil consumption, carbon buildup, and water pump failure. Additionally, we’ll discuss overall reliability in more depth below.

Northstar Engine Problems

• Blown Head Gasket
• Rear Main Seal Oil Leaks
• Valve Cover Oil Leaks
• Excessive Oil Consumption
• Carbon Buildup
• Water Pump Failure

1. Blown Head Gaskets

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
• Overheating
• 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. 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

3. Valve Cover Oil Leaks

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.

Failure Symptoms

• Oil leaking around the cover
• Burning oil smell
• Low oil levels
• Rough idling
• Cylinder misfires

4. Northstar 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.

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. Carbon Buildup Problems

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.

6. Premature Water Pump Failure

This is another common Northstar engine that isn’t at all unique to the Northstar. Water pumps tend to be a point of failure on quite a few modern engines, likely due to the fact that they are under high strain at all times. As the water pump is one of the most important components in an engine’s cooling system, a failing water pump on a Cadillac Northstar can be a significant issue if not addressed in a timely manner. While there is no way to predict a water pump failure, keep in mind that the 100,000-mile mark tends to be the point when you should think about replacing your Northstar’s water pump even if it hasn’t failed.

There have been reports of significant Northstar water pump leaks as early as the 40,000-mile mark, which is very early for a water pump to be failing. This leak can usually be spotted pretty early, as coolant will be leaking underneath the vehicle. A jump in engine temperature can also indicate that your Northstar has a water pump leak, so keep an eye on your temp gauge.

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.