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Inside Sealing GM Northstar Engines Who For shop owners and technicians What Tips for engine sealing repairs Where Visit www felpro only com for more information Why Leverage the expertise of the Fel Pro engineering team to gain a better understanding of this important and often misunderstood GM powerplant Highlights Introduction to the Northstar design Ensuring a lasting head gasket seal Finding hidden problems during the repair Choosing the right valve stem seals The Northstar family of engines represents the zenith of GM engineering from the 1990s and well into the current decade Introduced in 1993 for the automaker s luxury vehicle platforms this family of all aluminum V8 powerplants marked a true departure from previous engine designs in terms of overall architecture output per litre and sealing technology Although Northstar engines are viewed within the aftermarket as challenging they do offer a wealth of opportunity for engine professionals who are willing to learn about them and work on them The technical recommendations and products featured in this bulletin are based on extensive customer input to Federal Mogul s engine sealing team In addition the company s Fel Pro product engineers in Skokie Ill work closely with engine specialists within Federal Mogul s global network of technical research facilities to develop innovative solutions to the latest sealing challenges encountered in the repair environment Common Sealing Issues Among the most commonly reported Northstar sealing issues are 1 Cylinder head gasket failure 2 Manifold gasket leakage 3 Valve stem seal material choice Fel Pro Solutions 1 PermaTorque expanded graphite cylinder head gaskets with stainless steel combustion armors 2 Multi layer steel MLS exhaust manifold gaskets 3 FKM Viton positive type valve stem seals with installation aid Finding Opportunity in a Revolutionary Engine Platform GM Northstar 4 6L 4 0L Application Engines in Service 1993 2004 4 6L 2 322 902 1995 2003 4 0L 157 037 FPO 0508 151 www felpro only com A Look Inside the Northstar By John Gurnig Field Test Technician Depend ing on who you re talking to the GM Northstar Premium V V8 engine platform is either one of the best or one of the worst ever to come out of Detroit Many Cadillac enthusiasts rave about the power and response of this innovative powerplant Oth ers complain about chronic oil leaks and head sealing issues But most will agree on one point Finding a shop that will tackle a Northstar repair is next to impossible The reluctance of many engine professionals to perform Northstar repairs is largely due to a lack of understanding of this sophisticated engine plat form In fact for the first three years of production GM prohibited dealership technicians from perform ing internal repairs on Northstars preferring to send factory specialists to do this work A Different Animal The Northstar is indeed very different from most other engines but it also offers ample opportunity for aftermarket shops to in crease their market share There are probably many loyal Northstar owners in your area who are looking for a convenient source of quality aftermarket sealing repairs The differences in the Northstar begin with its construction a die cast aluminum 90 block massive one piece cast aluminum 16 valve DOHC heads lower crankcase assembly without conven tional main bearing caps and an oil manifold plate with a silicone gasket that serves as the oil gallery Many of these engines also featured a liquid cooled alternator until the 2001 model year At the time of its introduc tion the Northstar s most publicized feature was its innovative limp home mode which allows these engines to continue run ning for up to 50 miles at reduced output following a total loss of coolant The Northstar was used only in Cadillac models un til the introduction of a 4 0L version for the Oldsmobile Aurora in 1995 The engine family now consists of the original L37 4 6L model the transverse mounted LD8 the higher output LH2 the supercharged 4 4L LC3 and the 4 0L L47 used in the Aurora GM also developed a 3 5L V6 version the LX5 that was used briefly in the Oldsmobile Intrigue and Aurora Sealing Opportunities The Northstar is viewed by some as unrepair able Not true In fact sealing repairs among the most com mon service needs on these engines are well within the capa bilities of most well trained engine profes sionals But as with any modern engine it s absolutely vital that the technician begin the job with a deep understanding of the Northstar s unique design If you re going to repair a Northstar and there s no reason not to capture these service opportunities make sure you follow all of the manufac turer s recommendations and use only the best parts available John Gurnig runs the Fel Pro Field Test Garage in Skokie Ill He usually can be found under a hood out on a road test or back in the Fel Pro dyno lab GM Premium V engines are repairable as long as you know your stuff John Gurnig ENGINE MODEL YEARS APPLICATION L37 1993 Allante Eldorado ETC Seville STS DeVille Concours DTS DTS Per formance Buick Lucerne Super LD8 1994 Eldorado Seville SLS DeVille DeVille Concours DTS Buick Lucerne CXS Pontiac Bonneville GXP LH2 2004 SRX XLR STS LC3 Super charged 2006 STS V XLR V L47 1995 04 Oldsmobile Aurora LX5 V6 1999 02 Oldsmobile Intrigue and Aurora Northstar Engine Guide Head Gasket Repairs Given their all aluminum design Northstar engines aren t susceptible to the extreme casting motion associated with many high output bi metal engines There is moderate vertical motion however due to the comparatively high horsepower ratings of this engine family Most head gasket failures on these engines can be traced either to a cooling system issue or a loss of clamping force Clamping force deserves special attention The engine s head bolts are exposed to the elements over a significant portion of their length As the bolts are removed it is not uncommon for rust dirt and debris on these exposed areas to damage the block threads In fact thread damage is a primary concern on all Northstar engines In many cases the threads in the aluminum casting will bond to the fastener due to the countless heating cooling cycles encountered over several years of use As the bolts are removed some of the threads can literally be pulled from the block along with the fastener This damage might not be readily visible so carefully check all threads extending into the cylinder block assembly Then Heli Coil all suspect threads to ensure proper clamp loads Caution This is a torque to yield TTY application Cylinder head bolts must be replaced to ensure proper clamp load See the Fel Pro 900 Series catalog for a complete head bolt application listing Exposed Head Bolt Design Leads to Potential Problems Engine Years Ft Lbs 281 DOHC 4 6L 32 Valve Cadillac 2003 00 VIN Y 9 1st M11 bolts 30 2nd turn 70 degrees 3rd turn 60 degrees 4th turn 60 degrees 5th M6 bolts 8 8 281 DOHC 4 6L 32 Valve Cadillac 1999 98 VIN Y 9 1st M11 bolts 22 2nd turn 60 degrees 3rd turn 60 degrees 4th turn 60 degrees 5th M6 bolts 8 8 281 DOHC 4 6L 32 Valve Cadillac 1997 95 VIN Y 9 1st M11 bolts 22 2nd turn 60 degrees 3rd turn 60 degrees 4th turn 60 degrees 5th M6 bolts 8 8 281 DOHC 4 6L 32 Valve Cadillac 1994 93 VIN Y 9 1st M11 bolts 22 2nd turn 90 degrees 3rd turn 90 degrees 4th M6 bolts 10 244 DOHC 4 0L 32 Valve Oldsmobile 2003 01 VIN C 1st 30 2nd turn 70 degrees 3rd turn 60 degrees 4th turn 60 degrees 5th M6 bolts 8 8 244 DOHC 4 0L 32 Valve Oldsmobile 1999 98 VIN C 1st 30 2nd turn 70 degrees 3rd turn 60 degrees 4th turn 60 degrees 5th M6 bolts 8 8 244 DOHC 4 0L 32 Valve Oldsmobile 1997 VIN C 1st 22 2nd turn 60 degrees 3rd turn 60 degrees 4th turn 60 degrees 5th M6 bolts 8 8 244 DOHC 4 0L 32 Valve Oldsmobile 1996 95 VIN C 1st 22 2nd turn 90 degrees 3rd turn 75 degrees 4th M6 bolts 8 8 Northstar Torque Specifications The Fel Pro head gasket offered for Northstar engines features an advanced expanded graphite design a material particularly well suited to the amount of casting motion encountered in these engines This gasket features stainless steel combustion armors and a clear silicone topcoat Stainless steel armors are used for increased temperature resistance and their ability to resist cracking over millions of combustion cycles Repair Tips Intake Manifold Watch for Hidden Debris If you re repairing the top end of a Northstar engine due to a valve related issue burnt valve tim ing problem etc there is a strong possibility that a backfire occurred through the intake side of the engine This deserves special attention because the complex intake mani fold casting may hide stray pieces of metal or carbon This stowaway material can later become dislodged and end up in the combustion chamber causing damage to the valves piston head and cylinder walls Thoroughly inspect the manifold and replace if necessary Exhaust Manifold Seal with Fel Pro MLS Fel Pro engi neers recom mend using a multi layer steel MLS exhaust manifold gasket on this performance style engine The MLS gaskets offered by Fel Pro provide a robust seal be tween the cylinder head and the exhaust manifold The spring action of this MLS technology ensures the ability to maintain con tact pressure between the head and manifold as they expand and con tract at different rates Timing Parts Protect Yourself Pay close attention to the timing chain gears and tensioners when servicing the top front of Northstar engines Inspect ing replacing these parts now is a great insurance policy against an unhappy customer This is not a free wheeling engine so a hiccup in the valvetrain can cause the valves to hang in the combustion chamber and hit the pistons Per form this inspection repair now Valve Stem Seals Material Matters There s a huge dispar ity in the valve stem seal materials offered in the aftermarket Use only qual ity FKM rubber positive type valve stem seals such as those included in Fel Pro Head Sets and Valve Stem Seal Sets SS Using lower cost seals in a North star engine is an invitation to trouble Note that Fel Pro Head Sets HS and Valve Stem Seal Sets also include seal instal lation aids which are installed over the keeper groove area of the valve PRIOR to seal installation to prevent damage to the inside lip of the seal Once the seal is installed the aid can be discarded Only Fel Pro offers 100 application specific sealing solution components for Northstar engines Each Fel Pro gasket and seal for these applications features the best material and design for the aftermarket repair environment Northstar Engines Parts Check Exhaust System Exhaust Manifold Gaskets Exhaust Pipe Gaskets Fuel System Throttle Body Gaskets Leak Repair Camshaft Rear Seals Crankshaft Front Seals EGR Exhaust Air Supply Gaskets Intake Manifold Gaskets Oil Pan Gaskets Rear Main Seals Valve Cover Gaskets Cooling System Thermostat Gaskets Water Outlet Gaskets Water Pump Gaskets Drivetrain Rear Axle Housing Gaskets Transmission Pan Gaskets Engine Repair T T Y Head Bolts Head Gaskets Head Gasket Sets Valve Stem Seals Conversion Gasket Sets Repair Type Repair Type Premium Materials Viton Valve Stem Seals PermaDry Oil Pan Gaskets PTFE Rear Main Seals PermaDry Valve Cover GasketsViton is a registered trademark of the E I DuPont Company
