Porsche M96/M97 engine: faults and reliability

• 2.5 Boxster 204 hp (M96.20, 1996-1999)

  1996–1999 · 204 hp · M96.20

  With caution

  Stuttcars places the porous blocks and cracked liners in the 2.5 of 1997-1999, although auto motor und sport considers the smaller Boxster engines the least prone to failure; check for white smoke on start-up and ask for the service history.^[10][11]

• 2.7 and 3.2 S Boxster 220-258 hp (M96.21/.22/.23/.24, 1999-2004)

  1999–2004 · 220–258 hp · M96.21, M96.22, M96.23, M96.24

  With caution

  Those from 2000-2005 have the single-row IMS bearing, the highest-risk one according to Flat Six Innovations; ask for proof that it has been upgraded and check the rear seal.^[2][10]

• 3.4 Carrera 300 hp (M96.01/.02/.04, 1997-2001)

  1997–2001 · 300 hp · M96.01, M96.02, M96.04

  With caution

  Auto motor und sport places the engine damage mainly before the facelift, and RennsportKC advises avoiding the 1999 996 because of cracked liners and cylinder heads; the double-row IMS of 1997-1999 fails less than the later one.^[2][12][13]

• 3.6 Carrera 320 hp (M96.03, 2002-2005)

  2002–2005 · 320 hp · M96.03

  With caution

  It has the single-row IMS bearing of higher risk (2000-2005, according to Flat Six Innovations) and Motorious considers it somewhat more prone to scoring the cylinders than the 3.4; you need proof of an upgraded IMS and an inspection with a borescope.^[2][14]

• 3.6 and 3.8 S of the 997.1, 325-355 hp (M96.05 / M97.01, 2004-2008)

  2004–2008 · 325–355 hp · M96.05, M97.01

  With caution

  Auto Bild sees the cylinder problem as even more marked in the 997.1 than in the 996, and Renn Driver associates it mainly with the 3.8 of the Carrera S; the large IMS bearing cannot be upgraded without opening the engine. Ask for a borescope inspection before buying.^[3][9][15]

• 2.7, 3.2 S and 3.4 S of the 987.1, 240-295 hp (M96.26 / M97.21 / M97.22, 2004-2008)

  2004–2008 · 240–295 hp · M96.26, M97.21, M97.22

  With caution

  Goodwood cites IMS problems in 987.1 models before 2009, with an incidence that seems lower than in earlier Porsches, and cylinder scoring mainly in the 3.4s; Foreign Automotive describes oil consumption and cold-start noise from cylinder 6 in those 3.4s.^[16][17]

Buy: No known serious faults, or they have already been corrected, in this version. With caution: Worth buying if something specific is verified: history, a replaced part or a completed campaign. Avoid: High risk of a serious fault that is hard to check for or prevent.

1. 1Critical severityFrequency: OccasionalTimingFailure of the intermediate shaft bearing (IMS) on the M96/M97Yes: the intermediate shaft bearing (IMS) can fail and destroy the engine. Wikipedia records failure rates of up to 8% revealed in the Eisen class action over the 996; the risk is concentrated in the 2000-2005 M96 with the single-row bearing and is lower, but real, in the large non-repairable bearing of the M97.
2. 2Critical severityFrequency: OccasionalCylinder head and blockScored cylinders (bore scoring) and ‘Kolbenkipper’ on the M96/M97Yes: in the 3.4, 3.6 and 3.8-litre M96 and M97 the cylinder walls can score, with a ticking at low revs, blue smoke and oil consumption; it is confirmed with a borescope and, if serious, requires rebuilding the engine. Sources disagree on how many engines are affected.
3. 3Critical severityFrequency: OccasionalCylinder head and blockPorous blocks and cracked or displaced liners in the first M96sYes, in the first M96s: Wikipedia records cracked or displaced cylinder liners and porous blocks that mixed oil and coolant, corrected with a minor redesign at the end of 1999. Stuttcars places them in the 2.5s of 1997-1999 and RennsportKC advises avoiding the 1999 996.
4. 4High severityFrequency: OccasionalCoolingComposite-impeller water pump that breaks up and clogs the coolant circuitYes: the composite impeller of the factory water pump can break and spread fragments through the circuit, clogging the cylinder head passages, creating hot spots and, according to Flat Six Innovations, possibly cracking cylinder heads.
5. 5Medium severityFrequency: CommonLubricationLeak from the rear crankshaft seal (RMS) on the M96/M97Yes: the rear crankshaft seal (RMS) often leaks oil on the 996, Boxster and 997.1. It usually starts as a sweat on the gearbox bell housing and can contaminate the clutch; Porsche's redesign with a PTFE seal greatly reduced leaks.
6. 6Medium severityFrequency: CommonLubricationAir-oil separator (AOS) failure: blue smoke and oil consumptionYes: the air-oil separator (AOS) and its hoses degrade with heat and let oil into the intake, causing blue smoke, uneven idling and oil consumption; in the worst case there is hydrolock. It is a cheap part, but awkward to replace.
7. 7Medium severityFrequency: CommonCoolingCoolant leaks: plastic expansion tank, pipes and fittingsYes: the M96's plastic expansion tank, located in the rear luggage compartment of the Boxster, cracks with heat, and the pipes and fittings of the cooling circuit age and drip; Auto Bild says the coolant problem gets worse on the 997.
8. 8Medium severityFrequency: OccasionalTimingWear of the VarioCam tensioner shoes and timing chains on the 996Yes, on the 996: the VarioCam camshaft adjuster shoes, which tension the chain, wear prematurely, as do the fourth and fifth chains. RennsportKC advises replacing them at around 100,000 miles (about 160,000 km); Flat Six Innovations warns if camshaft deviation exceeds about 4 degrees.
9. 9Low severityFrequency: CommonIgnitionIgnition coils cracked by heat and misfiresYes: the ignition coils of the M96/M97 crack with age and the heat of the engine and exhaust, causing misfires. Auto Bild notes that on the 997 they are also low-mounted and exposed to water splashes.

Severity colours: low, medium, high, critical. How we rate them

Manufacturer

Porsche

Family

Bóxer de seis cilindros refrigerado por agua de Porsche con inyección indirecta: M96 (Boxster 986 desde 1996, 911 996 desde 1997) y su evolución M97 (997.1 y Boxster/Cayman 987.1, hasta 2008). No incluye los Mezger del Turbo, GT2 y GT3 ni los de inyección directa MA1/9A1 (997.2, 987.2 y 991.1), que tienen ficha propia.

Fuel

Petrol

Displacement

—

Cylinders

6

Fuel system

Naturally aspirated

Injection

Indirect injection

Timing

Chain

Power

204–355 hp

Production

1996–2008

Makes

Porsche

Technical data^{[1][2][5][6][7][8][9]}

1. 1996–1999

   2.5 Boxster 204 hp (M96.20, 1996-1999)

   Porsche's first water-cooled six-cylinder boxer, 2.5 litres and 204 hp (150 kW) in the Boxster 986. Wikipedia cites cracked or displaced cylinder liners and porous blocks in the first engines, corrected with a minor redesign at the end of 1999.^[5]

2. 1997–2001

   3.4 Carrera 300 hp (M96.01/.02/.04, 1997-2001)

   The first 911 with water cooling: 3.4-litre boxer (3,387 cc) and 300 hp in the 996 Carrera, with two front side radiators.^[1][18]

3. 1999–2004

   2.7 and 3.2 S Boxster 220-258 hp (M96.21/.22/.23/.24, 1999-2004)

   The Boxster rises to 2.7 litres (220 hp) and the 3.2-litre Boxster S (250 hp) is added; in 2003 they go up to 225 and 258 hp. Wikipedia dates both capacities to 1999-2000.^[5]

4. 2002–2005

   3.6 Carrera 320 hp (M96.03, 2002-2005)

   With the facelift of the 996 Carrera, the boxer rises to 3.6 litres (3,596 cc) and 320 hp and introduces VarioCam Plus. Auto motor und sport dates the facelift to 2001, and the German Wikipedia dates the 3.6 to the 2002 model year.^[12][18]

5. 2004–2008

   3.6 and 3.8 S of the 997.1, 325-355 hp (M96.05 / M97.01, 2004-2008)

   The 997.1 fits the 3.6 (M96.05, 325 hp) in the Carrera and the 3.8 (M97.01, 355 hp) in the Carrera S. FCP Euro explains that M96.05 engines up to engine number 6950745 keep the repairable 996 IMS bearing, and that later ones and the M97 have a larger one that cannot be inspected with the engine fitted.^[7][9]

6. 2004–2008

   2.7, 3.2 S and 3.4 S of the 987.1, 240-295 hp (M96.26 / M97.21 / M97.22, 2004-2008)

   The 987.1 introduces the Cayman and keeps the 2.7 (240 hp, 245 hp from 2007), the 3.2-litre Boxster S (280 hp, 2005-2006) and the 295 hp 3.4 fitted to the Cayman S, which the Boxster S inherited in 2007. Wikipedia gives the codes M96.26 and M97.21/M97.22.^[8][19]

• Timing chain kit

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• Oil filter

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• Air filter

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• Spark plugs

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