Porsche M96 Engine Problems

The 4 Most Common Porsche Boxster 986 Problems

The first generation 986 Boxster was released in 1996, initially intended to be a successor to the poorly selling 928. The Boxster was designed in conjunction alongside the 996 Carrera and shares many of the same parts and features. Engine design, headlights, interior comments, and the hood/front end are all shared between the 986 and 996.

The 986 Boxster lived on until model year 2005 when it was replaced by the 987 Boxster. 

Boxster M96 Engine

Both first gen 986 and second gen 987 Boxsters use the M96 engine. The M96 engine came with 2.5L, 2.7L, and 3.2L displacements. 

The M96 engine is a water-cooled, naturally-aspirated flat-6. The Boxster used a mid-engine layout for a lower center of gravity, improved weight distribution, and better handling. The M96 was Porsche’s first water-cooled flat fix engine

2.5L M96 Engine

The 2.5 M96 (known as the M96.20) was used from 1997 until 1999. It produced approximately 200hp and 180 lb-ft. of torque. The initial 2.5 engine had a poorly designed engine block which would cause the cylinder liners to crack. Additionally, the cylinder cracks affected the cooling systems, mixing coolant with engine oil, causing additional performance related problems and overheating. 

Outside of the cylinder block design, Porsche had issues with the casting process. The cylinder sleeves were cast separate of the engine which is thought to be the reason for the cracking. Given the major issues, Porsche redesigned the engine in 1999 and increased its displacement to 2.7L.

2.7L M96 Engine

The 2.7L M96 debuted in model year 2000 as a replacement to the 2.5L. In addition to a newly designed engine block, Porsche improved upon the casting process to remediate the cylinder cracking issue. While cracking is less prone on 2000+ models, it hasn’t completely disappeared. It produced approximately 225hp and 190 lb-ft. of torque, a 25hp and 10lb-ft. increase over the 2.5 version.

Under the engine codes M96.22/23/25 the 2.7 lasted until 2006 (Boxster 987) when it was replaced with the 2.7L M97 engine. 

3.2L M96 Engine

The 986 Boxster S models received a higher-output 3.2L M96 engine which produced 249-261hp and 225-230lb-ft. of torque. The 3.2 M96 also lasted in the Boxster until 2006 when it was replaced by the M97 engine, where it received a displacement increase to 3.4L. 

Porsche 986 Boxster M96 Engine Problems

  1. Rear Main Seal Oil Leak
  2. IMS Bearing Failure
  3. Cracked Cylinders
  4. Cylinder Scoring

Porsche is known to be one of the most reliable car manufacturers out there, but that doesn’t mean they are perfect. While glamour, flashiness, and performance typically come along with owning a Porsche, so, too, does the price tag – not just in purchasing one but, also, in fixing one. In order to save you the hassle and the money, let’s look at some of the common problems that Porsche Boxster 986’s encounter and ways to reduce the likelihood of them occurring.

1. Boxster M96 Rear Main Seal Oil Leak

This is the main problem found amongst 986 Boxsters and typically occurs at the rear main seal on the M96 engine. The rear main seal sits where the crankshaft meets the clutch and gearbox. The seal prevents oil from the crankshaft getting into the transmission and damaging the clutch.

Unfortunately, despite numerous redesigns by Porsche, the seal is prone to deteriorating and causing leaks. While some leaks go unharmed and unnoticed, more serious leaks can destroy the clutch and other internal transmission components.

The seal can leak for a few different reasons. If you don’t drive your M96 frequently, the seal can dry out and form cracks that will cause the leak. Additionally, the air oil separator, which is an emissions system, can fail and cause the leak as well. When the air oil seperator fails, crankcase vacuum increases which sucks in excess air and damages the seal. 

Rear Main Seal Oil Leak Symptoms

  • Burning oil smell
  • Engine rattling / shaking
  • Excess oil consumption
  • Shifting issues and loss of performance
  • Oil leaking beneath transamission

Rear Main Seal Replacement Options

Replacing the rear main seal is not expensive in itself, but oftentimes will require you to replace the clutch. It can be a hassle, though, as fixing the issue is typically not a DIY project due to the fact that the transmission and exhaust have to be removed to replace the oil seal – making the labor more expensive and intensive than acquiring the part. 

The oil seal is a cheap part. It will likely leak at some point and they are meant to be replaced. The best way to prevent any damage coming from it, is to have the part replaced early. If you are having your car worked on by a mechanic for something else that requires the transmission be removed, have them replace the oil seal. Other basic preventative maintenance techniques are simply to frequently change your oil, and wait a couple minutes before turning your car off, especially after running it for a while on those hot summer days.

Using the latest and greatest seal, such as the rear main seal from LNE Engineering, can help prevent further leaks.

2. IMS Bearing Failure – 986 Boxster

IMS stands for intermediate shaft. The IMS bearing is a small piece that supports the IMS on the flywheel end of the engine. This small piece often causes large problems for Boxsters, 911’s, and Cayman’s from 1997-2008; however, due to upgrades the IMS bearing is a lot less likely to fail for models from 2006 to 2008. If this part fails, at the very least, you’re looking at having the engine removed, disassembled, and put back together. More likely, you are looking at a complete rebuild or replacement. 

The IMS bearing fails for two particular reasons. First, the material that the bearing is manufactured out of is not strong enough for the amount of force and load that is exerted upon it. Second, the bearing does not receive adequate lubrication. 

If you are looking at buying or selling a Porsche from 1997 – 2008 (especially pre-2016) do your homework on the car’s service history. Whether or not the car has an upgraded IMS bearing can be the reason for a large difference in its value!

M96 IMS Bearing Failure Symptoms

  • Metal shavings in oil
  • Knocking or rattling noises from the engine
  • Oil leaks in rear of engine

Unfortunately there aren’t necessarily any preexisting symptoms that can warn you that IMS bearing failure might occur. The most tell-tale sign of failure is metal shavings in the oil. This will generally be the first symptom to appear and then terrible performance and engine knocks all over the place will follow. And then the engine implodes, basically. 

Constantly check your oil for metal shavings during oil changes. If you catch the issue early on you can likely salvage some components from your engine vs. needing a complete teardown or new engine. 

IMS Bearing Replacement Options

The IMS bearing can fail at any time, regardless of mileage. Since there aren’t any warnings signs of IMS failure, our general recommendation is to upgrade the bearing before the problem occurs. 

The solution to this problem is expensive, but not in comparison to rebuilding the engine. You can replace the IMS bearing with an upgraded ceramic bearing, but this will typically run you a few thousand dollars. This is also a very labor intensive project, so it’s best to do this in conjunction with another labor intensive project such as replacing the rear main seal. 

IMS upgrade kits differ by engine so be sure to make sure you are ordering the proper kit before you buy. You can check out this guide to help determine what kit you need.

3. Cracked Cylinders – M96 Engine

This typically occurs for the 986 and 987 Porsche Boxsters. The liner around the cylinder cracks, usually, due to overheating from a loss of coolant. If you notice your car overheating, or your coolant running low. Fixing a radiator or a coolant hose is cheaper than replacing a cylinder. Furthermore, a cracked cylinder can lead to irreparable damage to the engine, in which case the only option is to replace or rebuild the engine. 

If you see or smell coolant leaking from your exhaust or notice your coolant and oil mixing, this is a sign of a cracked cylinder. Your oil will look like chocolate milk and be gooey. Keeping an eye on your engine temp, coolant levels, and replacing your water pump before it fails are the best ways to keep your cylinder from cracking.

M96 Cracked Cylinder Symptoms

  • Coolant leaking from exhaust
  • Oil is a milky white substance
  • Poor performance
  • Smoke coming from exhaust
  • Low cylinder compression

4. Porsche Boxster M96 Cylinder Scoring

Cylinder scoring is one of the most common issues with the M96 Boxster and occurs when a cylinder forms deep grooves on the liner. This is usually caused by a broken or defective piston dragging across the wall of the cylinder. 

If one of your exhaust pipes is way more black than the other, this is a sign that one cylinder is burning different fuel/oil mixtures. The main symptom of cylinder scoring will be a knocking noise that occurs from the piston dragging across the cylinder wall. 

A lack of lubrication in the cylinder and pistons is the most common cause of cylinder scoring. It’s important to change your oil every 3,000-5,000 miles and be cautious of oil levels in between oil changes. It’s not uncommon for 986’s to consume excessive amounts of oil so check in between services and make sure oil levels are always adequate. Additionally, take it easy on your engine RPMs until it gets up to operating temperatures.

Boxster 986 Cylinder Scoring Symptoms

  • Black coated exhaust pipe
  • Knocking noise from engine (sounds like lifter tick)
  • Oil within the cylinders
  • Cylinder misfires

Is the Porsche Boxster 986 Reliable?

After reading this, you may be a little scared to spend tens of thousands of dollars on a Porsche Boxster 986. It is important to remember that no car manufacturer is perfect and no car is either. The Porsche Boxster, though, has stood the test of time. There are thousands of Boxsters for sale out there ranging in price, age, and mileage – and oftentimes the older cars with more mileage are more reliable than the older ones with low mileage.

All in all, we give the Porsche Boxster an above average grade for reliability, and well above average with an IMS bearing upgrade and proper maintenance. Spending a little more time and money on preventative maintenance will save you tons of money and stress. After all, it is a Porsche, so spending a little more on maintenance is miniscule compared to what you will spend on repairs and replacements. 

Porsche M96 Engine Problems Summary

As with all cars, you can expect to replace parts from regular wear and tear, but we covered the main problems that are typically expensive to fix. At the end of the day, if you do your homework on the Boxster before you purchase one, get the IMS bearing upgrade (if needed), and take good care of your car you should expect the Porsche Boxster to run well and for a long time. 

Do you have a different experience? Other problems that have occurred for you? Or tips and tricks to improve the reliability? Leave a comment and let us and other readers know! 

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