Over-engineered. If you have not heard of this term, a dive into the history of GM’s Northstar engine should help. On sale for two decades, the Northstar engine has mustered a reputation for itself. What kind of reputation, you might ask. Sometimes good, sometimes bad. Allow us to clear it up for you.
History of Northstar Engine
Northstar engines were performance engines developed and manufactured by General Motors in the ’90s. Mostly revered for its applications in many Cadillacs, the Northstar engine is considered the most complex GM engine ever.
The Northstar engines were quite complicated for their time. In its initial years, it was considered to be engineering on the bleeding edge. But as it munched years, its intricate construction morphed into a convoluted puzzle for the mechanics.
The conception of the Northstar Engine Family
General Motors started scribbling on the drawing board for this engine in the ’80s. With banks filling up and people flaunting goldies, the luxury car market was about to blow up. With European makers already in the game and Japanese manufacturers like Lexus cooking up a revolutionary recipe like the LS400, GM had to act. It was not a knee-jerk reaction though. It took almost a decade for GM to imagine, design, engineer, market and roll out this mill.
With Oldsmobile’s R&D facility, GM started building a sophisticated engine that would stand its ground against the modern rival units. This was, on paper, a very good decision. Their aging Over Head Valve (OHV) engines was on their death bed and would not have lasted the fight. The existing OHV engines were also plagued with reliability issues, which also would not have helped the cause.
Engineering of the Northstar Engine
The Northstar engine was an engineering feat that was quite impressive as an idea. They were 90-degree V engines. The original Northstar engine was a V8 that came with a displacement of 4.6-liters (4,565 cc).
The first Northstar engine was a 4.6-liter V8 unit. In a V-engine, the cylinders are arranged in cylinder banks, angled against each other on a common crankshaft. In a V8 engine, for example, each of the two cylinder banks will have 4 cylinders placed in line. Each of these banks will be placed on a crankshaft at an angle from each other, forming a V.
The Northstar V8 had the same configuration and the angle between the banks was 90 degrees. These V8 engines were inherently balanced, and offered a smoother drive, compared to an inline engine.
Northstar engines did away with the old Over Head Valve configuration. In the old OHV engines, pushrods and rocker arms were used to control the valve motion. This proved to be ineffective as modern cars demanded more power. For more power, petrol engines needed to rev higher. An Over Head Valve engine was not capable of reaching higher revs.
Northstar engines rectified this issue by shifting to an Over Head Cam design. In this configuration, the camshafts are moved from the engine block to the cylinder head, controlling the valve from above. This made the valve motion quicker, ergo faster throttle response, and more power.
The Northstar engines employed four valves per cylinder. Instead of a single camshaft, they utilized two separate units. This is called a Double Over Head Cam engine (DOHC). While one camshaft actuated the intake valves, the other took care of the exhaust valves. With both camshafts working in tandem, these engines could rev even higher, producing more power.
DOHC engines also provided more control over the valve motion, paving way for better power delivery and fuel efficiency. The Northstar engines benefited from this technology, as it was a huge leap from their old pushrod engines.
Aluminum Block/Aluminum head
Northstar engines were modern engines. A modern move in automotive engineering of that time, that still runs strong now, is saving weight. Northstar engines utilized aluminum for the construction of their block and head, saving a considerable amount of weight.
With all this modern technology, the Northstar engines were expected to produce a decent amount of power. And it did. The first naturally-aspirated models churned out respectable power outputs ranging from 275 hp to 300 hp. This got hiked up as high as 469 hp in the supercharged variants that arrived later. The supercharged versions were also debored, with the total capacity reduced to 4.4-liters.
Interference Engine design
Northstar Engines were interference engines. Interference engines are made with no clearance between the top of the pistons and the valves. Non-interference engines leave room between the valves and the piston when it reaches the top dead center of the cylinder.
Interference engines are built to tighter tolerances. This allows the engine to make use of most of its volume, rev higher, and produce more power. But, on the flipside, interference engines could an absolute headache. Unfortunately, Northstar engines were known mostly for this trait of their interference design.
In any engine, a failure in the timing belt will cause the engine to stop. But the clearance between the valve and the pistons in a non-interference engine prevents a collision and saves itself.
But in an interference engine like the Northstar, if the timing belt fails for some reason, it can bring in some catastrophic outcomes. If in the middle of a drive, a failure in the timing belt can cause the pistons to crash into the valves. A bang, a pop, and a clatter are all you will hear before the engine finally let go. If this happens, an extensive rebuild will become necessary.
Sadly, Northstar engines’ interference design was just another nail in its coffin.
There were some features that made the Northstar engines peculiar, and the limp-home mode was one of them. This was a fail-safe method. These engines were capable of running without any coolant. In this worst-case scenario, the engine will route the fuel to only one cylinder bank. Meanwhile, the other bank will be air-cooled.
The Northstar engines had a massive oil capacity as well as an aluminum construction. These helped in better heat dissipation. With this tech, the Northstar engines could run for a maximum of 100 miles without any coolant in them.
Later Developments in the Northstar Engine
During its life of almost two decades, the Northstar engine range received a bunch of updates
The later Northstar engines were supercharged to squeeze out more power and torque, from a lower engine size.
Variable Valve Timing
A modern tech that allowed altering the valve timings. This helped the engine to adapt to the fuel demand, depending on the environment, throttle input, and a myriad of other factors. In the Northstar engine, it was capable of varying the intake valve by 40 degrees and exhaust by 50 degrees.
Direct coil-on-plug ignition
Each spark plug was hooked up to an individual coil. This arrangement helps the Engine Control Module (ECM) control the ignition to a closer degree. Achieving better power, fuel efficiency, and emissions were possible with this technology. It also eliminated the spark plug wires, a weak link in the spark plug assembly.
This was supposed to be a downgrade. The original models of the Northstar engines had a liquid-cooled alternator as a bid to prolong its life. But this posed the risk of coolant leaks and additional tubing. To improve reliability, GM swapped it for air-cooled units.
The Final Roll-out
The Northstar engine made its debut in the Cadillac Allanté, in mid-1992. The Allanté featured a V8 model of the Northstar, with an output of 295 hp. This was also accompanied by a healthy reserve of torque, at 290 lb.ft. The Allanté’s engine was the genesis of the long-range of engines to be used by Cadillac, Oldsmobile, and Buick, including a cameo in a Shelby.
Northstar Engine versions
The original Northstar engine plonked in the engine bay of the Cadillac Allanté was the L37. The 295 hp output in the Allanté went up to 300 hp in the STS, DTS, and ETC Cadillacs, from 1996 through 2004. The L37 was transversely mounted for a front-wheel-drive layout. The Northstar engine was a rarity as V8s are normally reserved for rear-wheel-drive cars.
The L37 was a Northstar engine built for outright performance. The LD8 on the other hand focused on churning out more torque. It did not rev as much as the performance-oriented L37. Most of these LD8 Northstar engines produce 275 hp and 300 lb.ft. This engine was used in the 1994-2002 Cadillac Eldorado, 1996-2005 Cadillac Deville, 2006-2011 Cadillac DTS, and 2006-2007 Buick Lucerne.
This was the first longitudinally mounted Northstar engine. While originally designed for transverse-mounted front-wheel-drive applications, the LH2 allowed rear-wheel-drive/all-wheel-drive applications. This Northstar also received updates including continuously variable valve timing.
With this improvement, the LH2 Northstar V8 produced more power, 320 hp. It also churned out more torque, at 315 lb.ft. Developed in 2004, the LH2 Northstar engine found its home in the Cadillac STS, SRX, and XLR models.
This was a major update in the arena of forced induction. While all the previous versions of the Northstar engine were naturally aspirated, the LC3 came with supercharging.
Featured in the 2006 Cadillac STS-V and XLR-V performance models, the LC3 Northstar was capable of producing 469 hp and 439 lb.ft of torque in the STS-V. In the XLR-V, the outputs were slightly lower, at 443 hp and 414 lb.ft. As we mentioned before, this engine was also debored, dropping the capacity from 4.6-liters to 4.4-liters, in favor of additional strength.
This engine may not always be called a Northstar engine, but is largely based on it. Dubbed the Aurora engine, thanks to its application in the Oldsmobile Aurora from the year 1995 through 2004. It is an even smaller engine, at 4.0-liters, with outputs of 250 hp and 260 lb. ft.
This is also the Northstar engine that went on the racetrack. A 650 hp version of the L47 Northstar used in the Oldsmobile Aurora GTS-1 and Riley&Scott LMP prototypes entered the 1995 IMSA sports car competition by the GM racing division. It also raced in the 1997 Indy Racing League competition. In 2000, a twin-turbo version was seen being used in the Cadillac Northstar LMP program.
The L47 version of the Northstar engine also featured in a Shelby. The Shelby Series 1 made from 1999-2005 featured the L47 under its hood, with a decent output of 320 hp and 290 lb.ft.
We are straying even further from the familiar V8 Northstar engine formula. The LX5 Shortstar was based on the L47 Aurora V8 engine but it was a V6. It was technically a short Northstar engine, later called the Shortstar engine.
But do not be mistaken. This was not the exact L47 with two less cylinders. The entire cylinder block was engineered from the ground up, despite which it retains the 90-degree V-angle of the Northstar.
Dropping two cylinders brought down the capacity of the engine as well. The Shortstar displaced just 3.5-liters and produced 215 hp. The torque was also lower, at 234 lb.ft.
This engine debuted in the 1999 Oldsmobile Intrigue. It was also found under the hood of the Oldsmobile Aurora, playing second fiddle to the L47 Northstar V8, a.k.a the Aurora engine. The Shortstar was finally discontinued in 2004, making way for the newer High feature Engine.
But before it died, the Shortstar found its place on Ward’s 10 Best Engines list for 1999 and 2000. The V8 Northstar engines also found a place on this list, in the years 1995, 1996, and 1997.
The Final Northstars
After a long run spanning almost two decades, the Northstar engine came to its final leg in 2011. The last cars to sport a Northstar engine were the Buick Lucerne, Cadillac DTS, and the Cadillac STS. The Northstar was later replaced by the GM LS small-block OHV engine, switching back to the pushrod design.
The Northstar system
Northstar engine was way ahead of its time, we have all read about it. But with this new engine, GM also rolled out a package of features that made their cars even more modern. The Northstar package was introduced in the 1993 Cadillac Allanté and then in 1993 Cadillac Seville and Cadillac Eldorado.
The Northstar system consisted of components for different areas of the vehicle. Engine, transmission, brakes, suspension, steering, the lot. With this package, GM planned to make the cars as modern as possible. This was to create an offensive against the upcoming Japanese and European luxury cars.
The Northstar system included
- The Northstar engine: It was either the original L37 or the LD8 engine that featured in this package.
- Variable Valve Timing: These engines offered continuously varying valve timings, for better fuel efficiency.
- GM 4T80-E 4-Speed Automatic Transmission
- Road Sensing Suspension (RSS): This system used sensors to measure the shock absorbers’ damping rates every 15 milliseconds. Depending on the road surface, the damping was changed between two settings. There was an advanced CV-RSS system available in some cars.
- Bosch Anti-lock Braking System and all-wheel disc brakes
- Speed-variable power steering from Magnasteer
Northstar Engine Problems
So, if the Northstar engine was an example of modern engineering, why is it so heavily criticized on online forums? Simple answer, it was bad modern engineering. But it is not that easy to say. As the Northstar engine was used in a flurry of GM cars, it will be a blanket statement if we say that it was an unreliable motor.
If you have the habit of sifting through Craigslist for used cars on a dismal budget, you may have come across a bunch of Northstar-equipped models. For so many cars with the same engine to fetch such little resale value, there should be a common issue with the engine. And yes, there is. But unlike a modern unreliable GM car like the Chevrolet Cruze, the Northstar engined machines mostly faced one key issue.
This is the major issue everybody highlights in almost all forums when they talk about the Northstar engine. This was a prevalent issue in the engine and this was one of the major reasons that brought down the popularity of the Northstar.
If the Northstar engines run too hot, the head bolts would easily pull out of the engine block. These single-use torque-to-yield bolts were too slender and smooth. These bolts, permanently stretch once they are tightened to place. In an overheating scenario, this stretching increases, causing them to pull out.
When the head bolts pull out, coolant could leak out. This reduces the amount of coolant that cools down the combustion chamber, overheating the engine. Even when the engine cools down, the stretched bolts retain the stretch, permanently leaving a gap. This can blow the head gasket.
The limp-home mode would have helped the Northstar save the engine from some bit of overheating but when it does overheat, the engine had such tight tolerances, paving way for a colossal repair job.
How to spot this issue?
Like any other vehicle, the engine temperature gauge and coolant level indicator are the primary indicators of an overheating engine. Plumes of smoke from the exhaust pipe or needing to top up the radiator constantly are also bankable warnings.
If you spot any of these warnings, it is advised to stop the vehicle immediately. Forget not, do not trust the Northstar’s limp-home mode. That may not help you in this scenario.
Which engines had the most trouble?
The head gasket issues were most prevalent in the Northstar engines from 1997 to 1999. In 2000, Cadillac tried to address this issue by increasing the lengths of these bolts. This actually helped to reduce the chances of blowing a gasket but it did not eliminate it.
In 2004, they finally replaced the notorious bolts. They were swapped with LS6 head bolts which were longer than the original bolts and featured a coarser thread. Due to this modification, the 2005-2011 Northstar engines had fewer gasket issues. In fact, it was no less reliable than other aluminum V8 engines.
What is the fix?
The only sensible repair job is to replace the head gasket and the dreaded TTY bolts. This, in a regular car, costs a bomb to carry out. But in the “over-engineered” Northstar, it costed the bomb and its launcher.
The Northstar engines were packed so tight in the engine bay. Thus, the only way you could change these components is by dropping the engine. This would cost the owner an arm and a leg. Exact estimates are hard to find, but ballpark figures hover around $4000-$5000. This can be more than the actual value of the whole car in the used market.
This made the task of repair even more difficult. Hence, Youtuber Car Wizard called the Northstar engine, the Dumbest design.
Other Northstar Engine Problems
Apart from the head gasket issue, Northstar engines used to have some other minor issues as well.
Northstars are known for their excessive oil consumption. Pre-2000 Northstars may drink up to a quart of oil in just 500 miles. The piston rings in these cars can have carbon buildup in them, leaving an incompetent seal. This increases the oil consumption
The earlier Northstars can develop leaks around the seals and valve covers. It goes without saying that oil levels can drop in this engine. The owner may have to replace these seals and gaskets.
Carbon buildup in cylinders
The carbon buildup in the piston rings was solved by GM by 2000. But this job created yet another carbon-related issue. The 2000 and 2001 Northstar engines are found to develop carbon buildup inside the cylinders. This causes the engine to underperform during hard acceleration.
Is the hate on Northstar engine warranted?
So, what do we know? Back when it was launched, Northstar engines were not like the hardy, iron-block engines that everybody was familiar with. It was made to tighter tolerances, making it a finicky, high-maintenance engine to live with.
It had its own fair share of problems, the most acute of which is the head gasket issue. This could have been easily solved by swapping the bolts out for stronger ones. But dropping the engine to replace the bolts and gasket made it an unnecessarily expensive affair.
The unreasonable expense for the repair job was almost always higher than what the whole car is worth. Hence, most owners chose to dump the car instead of funneling money into it. This only worsened the already notorious appeal of the Northstar engine.
The Northstar engines are definitely expensive to live with. But if you are in the market for a modern American engine, stick to Northstars beyond 2005.
Feature image via VX1NG at wiki.commons (CC BY-SA 3.0).
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