M96 Family

Porsche M96.79
Porsche M96.79 – photo by The Car Spy

Porsche M96 Family

All Engines

Problems

  • Air-oil separator (AOS) failure – generally identified by the car blowing blue smoke from the exhaust. This is very expensive to fix, as it generally requires dropping the engine. Expect to pay $1k+ for repairs at a reputable shop.
  • Water pump failure
  • Motor mounts wear out, but they are easy and cheap to replace. Worn motor mounts can be identified by sagging/uneven exhaust tips.

Not Problems

  • Oil consumption – it is not unusual for these cars to go through a quart of oil in between changes
  • Occasional puffs of smoke on cold starts – this is something that has plagued Porsche flat-six engines for years. After sitting, the car may blow out a puff of blue smoke on a cold start. As long as it is not a frequent occurrence and does not persist after startup, this is NOT an indication of bore scoring or AOS failure.

Naturally-Aspirated Non-GT3 Engines (M96.01-05, M96.20-26)

Additional Problems

  • Intermediate shaft (IMS) bearing – read below
  • Oil starvation:
    • When fitted with sticky tires and driven at high speeds on tracks, the high G-forces can starve the engine of oil, leading to catastrophic failure
    • It is highly recommended to install an inexpensive “deep sump kit” if you plan on racing or doing track days
    • This is not an issue for street driving, or even for low-speed competitions such as autocross.
  • Bore scoring:
    • If the vehicle is driven primarily for short trips and isn’t allowed to run at operating temperature for a few minutes, it can eventually lead to bore scoring, in which the cylinder walls get scored and cause the engine to lose compression, necessitating an expensive rebuild or replacement
    • This allegedly affects 3.4L engines the most, but it isn’t anywhere near as common on the M96 as on the M48.00 engine.
    • Cars with severe damage will generally blow out blue smoke from the exhaust, caused by burning oil. However, a borescope inspection as part of a PPI is still recommended (though not compulsory).
    • To avoid issues, simply let the car fully warm up and run at operating temperature for a few minutes before shutting it down.
  • Rear main seal (RMS) – It’s not uncommon for this to start leaking oil, though leaks are usually minor. Unfortunately, repair requires removing the transmission. Usually, it’s best to leave it alone until a clutch or IMS bearing replacement, and top up oil in the meantime if necessary.

Intermediate Shaft (IMS) Bearing Issues

Background

Porsche’s engines had intermediate shafts for decades prior to the M96 engine, and they never posed a problem. However, for the M96 engine, Porsche decided to use a grease-fed roller bearing for the IMS with “lifetime” seals. Unfortunately, these “lifetime” seals tend to leak, allowing the grease to escape but not allowing engine oil in. The bearing loses lubrication and fails, usually causing the engine to go out of time, which results in catastrophic engine damage.

Replacement of the bearing requires removal of the transmission. As such, it is generally recommended to do it at the same time as a clutch replacement, and to also replace the rear main seal at the same time.

IMS Bearing Types
  • Dual-Row – This was the original M96 IMS bearing. It is generally considered to have low failure rates, and many people opt not to install any preventative measures as a result. However, they can still fail. These are present on all cars through MY99, and in some MY00-01 cars.
  • Single-Row – In MY00, Porsche began to use single-row IMS bearings in their engines. These are considered to be the most failure-prone, as they cannot handle as much stress as the earlier dual-row bearings. Some MY00-01 vehicles have these, but it is impossible to tell simply based on engine serial number – the only way to be sure is to remove the bearing. All vehicles produced MY02-05 have single-row bearings.
  • “Big Bearing” – In MY06, Porsche introduced the so-called “big bearing” on their engines. These are far less susceptible to failure than previous iterations, as they are actually located within the engine block. Failure almost always occurs only in vehicles which spend a lot of time at the track or in other high-stress situations. However, unlike previous iterations, replacement requires completely tearing apart the engine.
Solutions

These are in order from least to most effective.

  • IMS Guardian – This is a magnetic chip detector that installs into the oil sump drain plug. It sounds an alert when it detects metal shavings in the oil (a common symptom of early IMS bearing failure). If you want to avoid the expense of preventative IMS bearing repair, you should install this so that you have at least some chance of saving the engine should the bearing fail.
  • IMS bearing seal removal – Some people believe that simply removing the seal on the IMS bearing allows enough oil in from the engine to keep it lubricated.
  • Factory bearings – Some people elect to replace the IMS bearing with a factory one every time they perform a clutch replacement.
  • Upgraded bearings – Pelican Parts and LN Engineering sell upgraded bearings which they claim are stronger than the factory bearings. These have maintenance intervals, and are generally best changed with the clutch. This is the recommended minimum course of action.
  • Oil-fed bearing conversion kits – TuneRS, LN Engineering, and European Parts Solution (EPS) make kits that convert the original greased IMS bearing into an oil-fed bearing. Your mileage may vary. These are considered “permanent” solutions, in that they do not treat the IMS bearing as a maintenance item to be replaced after a certain number of miles (unlike the aforementioned upgraded bearings).
    • EPS’s kit converts the IMS bearing from a roller-type to a cylindrical roller-type. Of the three, its oil feed is the simplest, with just a small hole punched between the IMS front cover and the oil pump. There are questions about its effectiveness, but EPS claims to have no failures thus far.
    • The TuneRS kit is the most straightforward of the three. It does not change the bearing itself, but simply adds an oil feed.
    • The LN Engineering kit is expensive and involves a raft of other changes to the engine, claiming to fix a number of other issues in addition to IMS bearing failure. It converts the IMS bearing from a roller-type to a plain bearing, in addition to making it oil-fed.

Usage

M96.01/02/04

M96.03

M96.05

  • Porsche 911 Carrera, Carrera S (997)

M96.20/22/23

  • Porsche Boxster Base (986)

M96.21/24

  • Porsche Boxster S (986)

M96.25

  • Porsche Boxster Base (987)

M96.26

  • Porsche Boxster S (987)

Turbo Engines (M96.70)

Additional Problems

This section is still under construction, and may not have complete information.

Problems

These engines do not suffer from IMS bearing failure, bore scoring, oil starvation, or rear main seal issues.

  • The spindle on the turbocharger wastegate can seize, which causes excessive boost pressure and can lead to engine damage
  • Exhaust shields are prone to rattling

GT3 Engines (M96.76, M96.79)

These engines do not suffer from IMS bearing failure, bore scoring, oil starvation, or rear main seal issues.