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Porsche 968 Boxster

Boxster 986 common problems, performance modification and tuning guides.

Porsche M96 vs M97 Engine

November 12, 2021 by porsche 2 Comments

The Porsche M96 vs M97 engine differences are actually a hotly debated topic. Which cars use the M97 vs M96 and which engines have the fixed IMS bearing are two of the more controversial subjects. We’ll start off by covering the basics on each of the engines, the differences between the two, reliability & problems, and so on. And then we’ll provide our well-researched opinion on the IMS bearing and for what years it was “fixed”.

Both the M96 and M97 are engine families rather than specific engines. The M96 is the earlier version and was produced from 1996 through model year 2007. In model year 2005 the M97 engine started to make an entrance, phasing out the M96 engine. Additionally, both of these engines are used in the 986 & 987 Boxster’s and 996 & 997 Carerra 911’s. The M97 engine was also put into the 987 Cayman starting in model year 2007.

Porsche M96 vs M97 Engine

Porsche M96 Engine

The M96 made its introduction in 1996 as a 2.5L flat-six in the Boxster 986. Throughout its heyday from 1996-2005 it powered the Boxster (986 and 987) and Carrera 911 (996 and 997) vehicles. Impressively enough, the M96 came in 5 different engine sizes. The Porsche Boxtser vehicles had three options, a 2.5L, 2.7L, and 3.2L flat-six engine. The 911’s were equipped with larger 3.2L, 3.4L, and 3.6L flat-six options.

The 2.5L engine was only used from 1997-1999. The engine block was poorly designed and Porsche had some quality control issues in the factory that were leading to cracked cylinder liners. The 2.7L entered in 1999 as a replacement for the 2.5L. The 3.2L option was offered along side these smaller engines for “S” series cars.

The M96 engine receives a lot of criticism due to IMS bearing (intermediate shaft) failures, rear main seal leaks, and cylinder cracking. We’ll discuss these in more depth below. 

Porsche M97 Engine

Similar to the M96 engine, the M97 is a 24-valvve water-cooler flat-6. However, while the engine was built off of the same platform as the M96 it features a number of differences that we’ll cover below. The M97 was produced in 2.7L, 3.4L, 3.6L, 3.8L, and 4.0L engine sizes.

Starting in mid-2005 the 997 Carerra S began receiving the M97 engine. Until 2008 the base model 911 Carerra’s used the M96 engine which was eventually phased out in 2009 by the direct-injected MA1 engine. Both the 987 base Boxster and S series had the M96 engine in it until 2007 when they received the newer M97 engine.

The IMS bearing was purportedly fixed for the M97 engine. While failure can still happen and some people still have concerns with the bearing, the failure rate is lower than on the earlier M96 engines. However, M97 IMS bearing failure is a lot more costly as it requires the majority of the engine to be taken apart to get to it. 

M96 vs M97 Engine Differences

Although these two engines are very similar in nature there are some important differentiations. We’ll cover the big differences here and then provide some thoughts on the IMS bearings between the two since that is a debated topic. 

Increased Displacement

The first and most noticeable difference is that the M97 is a larger engine. While the Boxsters with the M97 still received 2.7L that was used in the base model, the Boxster S 3.2L was increased to a 3.4L, increasing power from 276hp to 291hp. The 2.7L received a small 5hp increase. When the 987 Cayman was released in 2007 it followed the same 2.7L base model and 3.4L S model structure.

For the 911 Carerra, the M97 was also still produced in a 3.6L size, similar to the M96. S models however did receive a larger 3.8L engine. And a 4.0L engine was produced specifically for the GT3 RS 4.0.

Displacement was increased by boring out the cylinders and fitting in larger pistons. Overall, the S models received larger engines while the base models kept the same sizes as the M96 predecessor with only minor power increases.

Adjusted Timing

Aside from the larger displacement, the timing was adjusted to create a smoother torque curve and to handle the power increases caused by the larger engine sizes. However, the intake and exhaust valves remain very similar to the M96 in terns of lift and sizing.

Jet Pump to Mechanical Pump

The brake booster vacuum pump for the M96 was a “suction jet pump”.  The details of how jet pumps work are rather technical, so you can read about it here if you’re intrigued. The M97 received an upgraded pump and switched from the suction jet design to a mechanical pump. Avoiding the technical differences, the mechanical pump provides more consistent vacuum supply and therefore a more consistent braking experience, especially when at altitude or when driving aggressively such as on a track.

Electronic Oil Level Sensor

The only way to check oil levels on the M96 engine is by pulling out the dipstick. It had no electronic oil monitoring. The M97 added electronic oil level monitoring so that you could see at all time where oil levels were at, the temperature of the oil, and oil usage. While not a major change oil level monitoring is a good feature to have to prevent serious engine damage from running low on oil. It is also helpful for detecting leaks.

M96/M97 IMS Bearing Upgrade

This topic is where the debate begins. We’ve done a lot of research on IMS bearings and will provide what we believe to be an accurate assessment. 

From 1997 until early 2005 the M96 engine used two different IMS bearing designs: the dual-row 5204 bearing and the single-row 6204 bearing. The 5204 bearing was used until early 2000 when it was replaced with the 6204 bearing. The bearing seals on the 5204 bearing deteriorated over time leading to failure. Failure was most commonly associated with age of the bearing and not necessarily mileage on the engine. 

Porsche changed the design in early 2000 due to failures and problems with the 5204 bearing. However, the single-row 6204 design is actually considered the least reliable of them all. So, in early 2005 a larger single-row 6305 bearing was introduced. It was bigger and stronger but still not bulletproof, albeit it is considered the strongest of the three.

So, Porsche fixed the majority of the IMS bearing issues in early 2005, although 2005+ IMS bearings are still susceptible to failure. But the number of cases of IMS bearing failures with the 6305 is a lot less than the predecessors.

So, which Porsche engines have the “fixed” IMS bearing?

Since the 6305 bearing wasn’t fitted until some time in the earlier part of 2005, there are some very early M97 engines that still have the bad 6204 bearings. The bearings were also upgraded for the M96 engine at the same time.

So, there are both M96 and M97 engines with old and new bearings on them. Anything with a build date of mid-2005 or later should have the better IMS bearing whereas anything before that will have the worst of the three. It isn’t clear exactly when the switch took place so it is difficult to say whether engines with early 2005 build dates have the new or old bearings.

The downside to the M97 engine’s IMS bearing is that it requires a complete teardown to access it, whereas you only need to remove the flywheel on the M96 engine to access it. While M97 IMS bearing failure is a lot less likely, it is a lot more costly to fix if it does break. 

Porsche M96 vs M97 Reliability

The most common M96 engine problems are IMS bearing failure, rear main seal oil leaks, cracked cylinders, and cylinder scoring. Unfortunately, the problems that are common with this engine are on the more expensive side to fix. IMS bearing and rear main seal issues are most common in old cars that haven’t been driven frequently and spent a long time sitting. So while a nice super low mileage M96 might sound tempting, the RMS and IMS are probably ticking time bombs. Fortunately, the IMS bearing can be preventively fixed. We’d give the M96 an average grade for reliability without the IMS fix, and slightly above average when it is fixed.

The vast majority of the M97 engines have the improved IMS bearing which gives this engine a leg up in reliability over the M96. Common M97 engine problems are cylinder scoring, cam solenoid failure, and coolant pipe failure. Most of the reliability issues with the M97 stem from the engine overheating and causing cooling system failures. When properly maintained and cared for, the M97 engine offers solid reliability.

Overall, the M97 is considered to be more reliable than the M96, predominantly since there are a lot less M97’s out there with the old IMS bearings. A 2005+ M96 will be pretty comparable to the M97 in terms of reliability since both with have the stronger and improved bearing.

Porsche’s are unfortunately very expensive to fix. And in terms of reliability costs, the M96 wins since it is a bit cheaper and easier to service compared to the M97. Overall, these are both great engines. But proper maintenance and care is vital for them to remain reliable.

Filed Under: 986 Boxster, M97 Engine

The 4 Most Common Porsche Boxster 986 Problems

June 10, 2021 by porsche Leave a Comment

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! 

Filed Under: 986 Boxster

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