Abandoned History: Cadillac's Northstar V8, Head Bolts and Gaskets Aplenty (Part V)

After a delayed and limited roll-out of the new Northstar engine (in two power configurations) for the 1993 and 1994 model year, Cadillac enjoyed a wave of positive press. With an entirely new product portfolio in place by 1994, the Northstar-filled (except Fleetwood Brougham) Cadillac lineup was ready to roll through the remainder of the Nineties. Cadillac immediately set about tweaking their V8 for 1995, and it was around that time some issues began to poke holes in the Northstar’s trophy collection.

The Seville STS was Cadillac’s flagship product when it debuted for the 1992 model year. It kicked off the award winning period for the brand. However, the ‘92 that won all those accolades was indeed the 4.9-liter equipped version, as Northstar was not ready until 1993. 

Even Cadillac’s own PR video (for Northstar) skipped over this little fact, and lumped the ‘92 STS in with the other Northstar awards. The “European sports sedan” class was where every OEM wanted to be at the time. Magazine comparison tests of the day pitched both larger and smaller sedans of type against one another; sometimes unfairly. Seville STS, Acura Legend, Nissan Maxima, Mercedes-Benz 190 and 300, Lexus ES, Lexus GS, Lincoln Continental, Jaguar XJ, BMW 5-Series, Infiniti Q45 and J30, Mazda Millenia, and Oldsmobile Aurora. Pick and mix as you please for comparison content.

With regard to the new Northstar Cadillacs, 1993 saw automotive awards from the likes of Autoweek, MotorWeek, Popular Science, Business Week, Automobile Magazine, Modern Metals Magazine, Consumer’s Digest, Robb Report, United Press International, Popular Mechanics, and even Rolling Stone. The awards ranged in scope from best engineering, top 10 of the American luxury segment, design awards, and comparison test wins. Rolling Stone gifted the STS its “Hot Car Award.” They don’t seem to rate cars anymore, though. 

The 1993 and 1994 Northstar engines were the “original” versions. As we covered in a previous entry, the magnesium intake manifold lasted through only the first year of engine production. Tricky construction with magnesium and the metal’s less than impressive durability properties were the reason Modern Metals Magazine saw fit to give an award to Northstar. Immediately replaced in 1994 with a plastic intake manifold, Cadillac engineers set about tweaking both versions of the Northstar for 1995.

The high-spec L37 received a bump in power for its 1995 usage, from 295 horses and 290 lb-ft of torque to an even 300 horses and 295 torques. In 1995 the L37 model list included the Eldorado ETC, Seville STS, and DeVille Concours. Allanté faded away after 1993, with a single-year Northstar offering among other cost-cutting efforts. Allanté deserves its own series, which will happen on these pages.

For base model Northstar vehicles equipped with the LD8 version, power increased in 1995 from 270 horses to 275, though torque remained at 300 lb-ft. The intent was to differentiate the LD8 as more focused on torque than the high-po L37. Whether drivers noticed those 5 total torques was debatable. 1995 models with the LD8 were the Eldorado ESC, Seville SLS, and DeVille.

It was around this time the earlier Northstar-equipped Cadillacs began to show issues. We’ll start with the lesser known one, coolant and oil seepage. According to an explanation on an ancient forum thread, the 1993 to 1999 Northstars had a problem with the integrity of their block castings due to the alloy used and casting methods. 

Specifically, as the block was made the molten aluminum splashed up the side of the casting, and then began to cool. The splashed aluminum cooled to the point that when the rest of the casting was filled with molten alloy, the cooler metal did not bond properly to the rest of the block. A fissure was created in this way, and allowed leakage. Oil and coolant would escape from early Northstar engines directly through the block. 

The broader and more visible issue a couple of years into Northstar were its various coolant loss issues, generally lumped together as “head gasket failures.” A misnomer in general, it was not the fault of the head gasket itself: The issue lay with the head bolts. Head bolts are long threaded bolts which attach the cylinder head to an engine’s block. 

In the case of the Northstar, the head bolts were threaded too finely, and lost their integrity with heat cycling and stress. This so-called “stretching” of the head bolts would cause them to strip the metal off the block as the threads pulled away. This resulted in a loss of cylinder pressure. Without cylinder pressure, coolant entered the cylinders, exhaust, and eventually the engine oil.

The loss of coolant caused the engines to overheat, which cooked the head gasket. While issues within the cylinders or exhaust were not always visible, a ruined head gasket led to milkshake-like brownish oil under the engine’s oil filler cap. The issues were then known generally as a head gasket failure, or the “Northstar Condition.” 

It could happen at any time, generally with miles between 50,000 and 100,000, and was more a when than an if condition. It didn’t matter how gently an early Northstar was treated, or how often it was serviced, it was going to fail eventually in this catastrophic way. Unfortunately for all involved, the fix for a failed Northstar was not a simple one. 

We’ll pick up with Northstar repair specs next time, and even take a little diversion into 4.9 land. It seems just as Cadillac stepped away from the 4.9 and went full problem-prone Northstar, it was hit with a slap in the face from the government. The old V8 had some secrets the brass at GM swept happily under the rug, and every single one of them would be sent back to a dealer service bay. Perfect time for an upsell to a new N* though, right?

[Images: GM]

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