Initially rated at 295 horsepower, the Northstar V8 has grown over theyears to an incredible 469 hp at 6,400 rpm (STS-V SuperchargedNorthstar engine).
In 1995, the engine was ranked as one of the “10 Best Engines in North America” by Ward’s Auto World. It repeated the honor in 1996 and 1997, but it hasn’t cracked the Top 10 list in more than 12 years.
Like most other engines, the Cadillac Northstar 4.6 V8 has evolvedover the years. In 1994, the first Northstar V8 (L37) was joined by asecond version (LD8) with a different cam profile that lowered peakhorsepower slightly to 270 hp but increased torque output in the lowerrpm range for improved throttle response and quick acceleration. Thatsame year, GM introduced a downsized and somewhat less powerful versionof the original Northstar V8 into its Oldsmobile Aurora.
The L47 4.0L V8 was essentially the same engine as the larger 4.6L V8,but with a smaller bore size (87 mm vs. 93 mm). And the L47 4.0L V8 wasrated at only 250 hp.
In 1995, the power rating of the L37 4.6L V8 (VIN 9) was bumped upslightly to 300 hp, and the LD8 4.6L V8 (VIN Y) was upped to 275 hp.Those two basic versions of the 4.6L V8 (275 and 300 hp) were used invarious Cadillac models for nearly 10 years.
However, in 2005, Cadillac engineers gave their Northstar a boost whenthey introduced a new 4.4L Supercharged Northstar V8 engine and GM’snew Hydra-matic six-speed automatic transmission. The official powerratings for the 2006 STS are 469 hp at 6,400 rpm and 439 lbs.-ft. oftorque at 3,900 rpm.
Theautomaker said that the Northstar V8 supercharged engine represents themost output ever for a production Cadillac. In fact, during the finalstages of development, GM Powertrain engineers found more opportunitiesto push the boundaries of the Supercharged Northstar engine.
The Supercharged Northstar V8, which also powered the V-Seriesedition of the XLR luxury roadster, generated more peak power for theSTS-V, compared to the XLR-V, due largely to the greater underhoodspace of the STS that allows more induction and exhaust capacity. Onthe other hand, the XLR-V will be a quicker car than the STS-V, givenits superior power-to-weight ratio.
However, according to GM, that engine is no longer available for new Cadillac models.
And, while the 4.6 Northstar did make it into Cadillac’s 2010 models(DTS and CTS), it is unsure how long this engine will shine in theautomaker’s lineup. As automakers look toward more turbocharging ofsix-cylinder engines as a way to reduce fuel consumption in largervehicles, the Northstar may be on the verge of burning out.
Northstar’s Unique Engineering
The Northstar V8 has a die-cast aluminum 90° block with a bottom endgirdle that splits along the midline of the crankshaft bearings. Thistakes the place of the main bearing caps. For model year 2000, GM beganusing a new high pressure “squeeze” casting process for the lowercrankcase to reduce porosity in the aluminum, which may allow oil toseep through and leak (this has been a problem on some engines).
The cylinders have cast-in-place iron cylinder liners that are notreplaceable. Compression up to model year 2000 was a relatively high10.3:1. It was lowered to 10:1 in 2000. Each head has two camshafts(one intake, one exhaust) and four valves per cylinder (33 mm intakesand 29 mm exhausts).
Direct-acting hydraulic lash adjusters are positioned over each valve.The overhead cams are all chain-driven, and use an intermediate chainsprocket under the front cover to connect to the crankshaft. Threeseparate hydraulic tensioners are used to keep the cam chains tight.
The Northstar V8 is an interference engine, which means if a chainfails or is disconnected when the engine is cranked over, the valveswill hit the pistons. That’s something techs don’t want to happen withan expensive engine like this!
Finally, the intake manifold is Nylon 66 thermoplastic, which itsengineers explain that this helps cool intake air by conducting lessheat from the engine.
Fuel and Ignition
Fuel is delivered by sequential fuel injection with separate injectorsmounted under the engine’s top cover. Under the top cover you’ll alsofind the MAP sensor, intake air temperature sensor and fuel pressureregulator.
If the fuel pump relay fails on a Northstar V8, the engine shouldstill run because the fuel pump also can be energized through the oilpressure-sending unit.
A four-coil distributorless ignition with a waste spark set up providesspark to the plugs. Two crankshaft position sensors are used (A and B)plus a camshaft position sensor to provide timing inputs.
Both crank sensors are mounted in the block and the cam sensor islocated on the rear head in front of the exhaust cam. There’s also aknock sensor on the rear head between cylinders 1 and 3 to retardtiming if detonation becomes a problem under load.
Theignition system has two modes of operation: “module mode” and “ignitioncontrol mode.” In ignition control mode, the PCM controls ignitiontiming using sensor inputs. If there’s a problem in the PCM or with itssensor inputs, the module mode takes over and runs the engine with afixed 10° of advance.
The engine continues to run (essentially a limp-in mode) but with reduced performance.
In model year 2000, the DIS ignition system was changed to acoil-on-plug design, which eliminates the spark plug wires and wastespark. Each head has its own ignition module that fits in the middle ofthe valve cover.
Another unusual feature you may see is a liquid-cooled alternator onthe DeVille and Seville. Cadillacs are crammed with electricalaccessories that put quite a load on the charging system, so usingliquid cooling helps prolong the life of the alternator. In 2001, GMwent back to an air-cooled alternator to “eliminate the coolant tubesand potential leak points.”
Later updates to the engine included variable valve timing (VVT), whichGM engineers said can vary the intake valves by up to 40° and theexhaust valves up to 50° in order to increase power output. However,the VVT system was designed for the longitudinal LH2 engine and not forthe transverse front-wheel-drive (FWD) engine.
GM explained that horsepower output on the FWD engine was already maxedout and adding the VVT feature to it would create excessivetorque-steer issues.
Did You Know…
Another feature of the Northstar enginesis a “limp home” mode that allows the engine to continue running if allthe coolant is lost. If the PCM senses an overheating condition, ittemporarily disables up to half of the cylinders. This pumps enough airthough the engine to keep temperatures from getting hot enough to causeany damage. Even so, GM says the vehicle should not be driven more than50 miles in the limp-home mode.
One of GM’s goals with the Northstar program was to reduce maintenanceto a minimum. The engines are factory-equipped with 100,000-mileplatinum-tipped spark plugs and five-year/150,000-mile Dex-Coolantifreeze, and use chain-driven cams to eliminate the need to replacetiming belts. Except for oil and filter changes, there isn’t much tomaintain — unless something breaks.
The newer Northstar V8s use an “oil life monitor” light rather than aspecific mileage interval or service schedule to indicate when oilchanges are needed. The PCM tracks engine rpm, operating temperature,load, running time and ambient temperature to calculate oil life.
Up until 1999, the maximum oil change interval under ideal conditionswas 7,500 miles. In 2000, GM bumped the upper limit to 10,000 miles. In2002, they did away with the upper limit altogether stretching the oilchange interval to 12,000 miles or more, depending on operatingconditions. However, GM does say the oil should be changed at leastonce a year regardless of mileage.
Note: When changing oil on a 4.6L Northstar V8,keep in mind that this engine holds 7.5 quarts instead of the morecommon 4 or 5 quarts.
While the Northstar V8 is well engineered, like other engines they’vehad some problems. According to various sources, head gasket failuresare not uncommon. Nor is oil burning or oil leaks.
• Cadillac service bulletin 01-06-01-011 deals with oil burning on1996-’99 Northstar V8s. The cure, says Cadillac, is to do a ringcleaning procedure (seems those long oil change intervals weren’t sucha good idea after all). Cadillac recommends using GM cleaning kit (P/N12378545) and Kent-Moore J-45076 induction/evacuation tool to do thejob.
The cleaner is added into the cylinders through the spark plug holesand allowed to soak the rings for two hours. The cleaner and dissolvedcrud is then vacuumed out of the cylinders through the spark plugholes, followed by an oil change. Cleaning the throttle body and EGRvalve is also recommended.
• On 2000-’01 Northstar V8s, a buildup of carbon deposits in thecombustion chamber can cause a cold knock condition. Bulletin99-06-01-101A says to use top cleaner to remove the combustion chamberdeposits.
• No oil pressure on a 1993-’94 engine? Debris between the oil pressurerelief valve and its seat will prevent oil pressure buildup. The curehere is to clean or replace the pump (P/N 3543258), which is located onthe front of the engine.
• Oil leaks around the rear main crank seal have been a problem on some1996-’99 engines, so GM has developed a new rear main oil seal (P/N12556107) that should cure this problem. It’s a press fit seal thattakes a special tool (J-42482) to remove and install.
• In 1995, GM revised the original crankshaft balancer to providesmoother operation and longer durability. If the balancer is removedfrom the crankshaft for any reason, GM recommends installing the newer,improved balancer (P/N 12552437 or 12552436, depending on the engine).
• If you have to pull a cylinder head on a 1993-’99 4.0L or 4.6L Northstar V8to replace a gasket or do a valve job, do not reuse the old 11 mm headbolts. Also, GM has revised the head bolt torque values and tighteningprocedure as follows:
- In sequence, torque all bolts to 30 ft.-lbs.
- In sequence, rotate all bolts an additional 70°.
- In sequence, rotate all bolts an additional 60°.
- In sequence, rotate all bolts another 60°.
- Torque the front three M6 head bolts to 106 in.-lbs.
Because the Northstar V8s are aluminum, thread damage is not unusual.GM’s recommended thread repair kit is J42385-500 for main and headbolts, and J42385-2000 for other fasteners.
Information and photos courtesy of General Motors Corp.
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