Porsche Boxster Common Problems
Exhaust Rattle or Check Engine Light?
Listed below are Porsche Boxster common mechanical problems with their likely resolutions. These are the most frequent Boxster problems diagnosed by our repair shops over the years.
An accurate diagnosis of an issue by a Porsche mechanic typically saves you time and money – see our guide to local independent Porsche repair shops that can help. If you’re researching and considering buying a Boxster, our used car buyer guides highlight mechanical issues to be aware of before you complete a purchase. If you are considering making a DIY fix to the problem, the best resource for a step by step guide is here.
Clicking on each heading will give you more detail.
986 | 987 | 981
One of the most common, misunderstood and potentially destructive is an oil leak from the rear main seal. A leaking rear main seal shows in the center of the engine trans area and appears through the bell housing joint between them. The leaking seal will destroy a clutch in a manual car very quickly if not addressed.
Some caution – Vehicles that are stored often display a weep/leak from the seal during storage or at the initial startup in the spring. The seal needs the heat of driving to seal efficiently, so in some circumstances the leak can slowdown or stop during the driving season. Replacing the seal requires the removal of the transmission and in a manual car, replacement of the clutch at the same time is a good choice.
This is common on the older Boxster. A recurring check engine light under acceleration is the first sign. Subsequently, an engine rattle at startup becomes more prevalent. The typical cause here is a stretching of the timing chains and failure of the timing chain tensioner. The only solution is to replace the tensioner and the chains. This is an expensive job with engine out and the right timing tools are necessary to complete the work.
Find a local shop that can do the work for you.
There’s no doubt that a cheap sealed bearing of the kind that sits at the end of the intermediate shaft on a flat six has no place in a performance engine. However, the hype generated by LN Engineering over this bearing and the real world results don’t match. Yes, it’s a weak point and yes it will fail, but in the real world less than 5% have actually failed or can be directly linked to engine failure. We’ve replaced literally hundreds of the bearings over the years and have to confess we’ve only ever seen one that showed signs of potential failure. We’ve seen the pictures and heard the stories but never seen it ourselves.
We recommend you update it as a precaution and as a selling point – cars that have the updated bearing do command a higher resale value because of the hype. In a manual car, do the bearing as an extra to having the clutch replaced. Adding the bearing to a clutch job will add about $800. In an automatic car, the job is quite simple and can be done in one day.
Porsche vehicles have a number of common sources for leaking oil. Some of the most common include rear main seal (see below), valve covers, spark plug seals and turbo oil supply line seals. Less common are leaks from the cam seals and scavenger oil pump seal.
Valve cover leaks are obvious and fairly straightforward to fix on most models. Spark plug tube seals can be done at the same time as the valve cover – leaks from the spark plug tube seals are frustrating. Often, you wont see the oil initially as it’s sealed in by the coil on top of the spark plug. The tube fills with oil and causes misfires by destroying the plug and the coil. If you see oil on a plug or coil, always replace the seals.
Bad rear main seal or something else causing the problem?
Designed to extract oil from the crankcase gases and recycle the gases through the combustion path while returning oil to the sump, the aos has caused numerous issues on Porsche engines. As the membrane in the aos fails, oil is sucked into the intake. Initially this can show up as a check engine light for fuel adaptations or be deposited on the o2 sensors and causes emission faults. Of course, once it fails completely, the resultant huge clouds of white smoke are fairly obvious. At that point, it obvious what needs to be done. However, replacing the aos sooner rather than later is a good precaution.
A failing aos is the likely cause of rear main seal failure as it is in other VAG cars. Crankcase gas is not extracted well enough, pressure builds in the case under acceleration and escapes out of the rear main seal causing seal failure and the resultant oil leak.
A failing aos also causes oil pass into the intake and will cause the engine management to adjust fuel mixtures. The changing mixture can cause over fueling and lead to other more significant problems – See smoke at startup below.
A quick puff of smoke as you start the engine is not uncommon especially on the flat six engine. There are many theories and various thoughts as to why this happens – none are proven. What we do know is that re-built engines rarely display this startup smoke, so it’s definitely a sign of wear and tear – and it does progressively get worse with mileage.
Extended smoking at startup is more of an issue. Again, there could be a number of reasons why this happens, but it is usually a sign of wear in the cylinders. See cylinder scoring below. Sometimes, replacing the fuel injectors can help. Worn and leaking injectors cause fuel to sit in the intake path while the car is parked. The fuel leaking is not enough to cause starting problems, but it can be responsible for the smoke and wear in the cylinders – unburnt fuel washes oil off the cylinder walls causing wear on the piston rings.
It’s not a tick, it’s a rhythmic knock and usually shows up first on the passenger bank of the flat 6 engines. Wear in the piston rings and the liners of the cylinder have caused the piston to wobble. The wobble occurs at the bottom of the stroke and causes the piston skirt to drag against the cylinder wall causing scoring of the liner. The rhythmic knock is the piston changing position at the bottom of the stroke and hitting the liner. In many cases, even with the head off the engine, the scoring cannot be seen until the piston is removed – it’s way down at the bottom of the cylinder. Double check the guy who says he can see it through a camera passed down the spark plug tube!
The only solution here is replacement engine or rebuild and re-lining of the cylinders. Results from this can be fun – we made 425HP from a 4.0L engine rebuilt from a broken 3.6L – however, you’re going to need a $25K budget to start the project.
Porsches are often garage queens and not driven as much as they could be. During any down period the car will continue to use some battery power – usually more than would be expected from similar vehicles. This can very quickly lead to a flat battery. Losing battery power resets a number of systems and can cause unnecessary headaches. We recommend you use a battery maintainer any time you store or do not drive the car for an extended period – 2 weeks or more.
There are many causes of a Check Engine Light on older Porsche Boxster vehicles. One of the most common for the 6 cylinder engines is a failure in the O2 and MAF systems. Commonly front O2 sensors will fail and cause the MAF to attempt to compensate. This results in many folks just replacing the front O2 sensors. And within a few hundred miles the check engine light is back on. This is actually caused by the MAF failing. The recommended solution is to replace both the MAF and front O2 sensors at the same time. Always use the original Porsche parts – the aftermarket versions do not work.
Misfires can occur at any time and require diagnosis to identify which cylinders are misfiring and why. Common causes are worn spark plugs, cracks in ignition coils and oil leaking past the tube seals. The ignition coils on the earlier flat 6 engines were updated – low mileage older cars will commonly still have the old style coils. Fuel injector malfunction can cause a misfire, however injector failure of this nature is not so common on the flat 6 engines.
Watch out for this one – older low mileage cars often have the original spark plugs. Plugs that have been in the engine for more than 10 years can be very difficult if not impossible to remove. A stuck or broken plug in the head is an expensive problem to solve.
This is a common failure on older the Boxster and 911. Turning the key will not start the car or the key is stuck in the ignition. This is caused by a failure in the electrical portion of the ignition switch. Replacing the switch is fairly straight forward and typically solves the problem immediately. On some occasions it may be necessary to replace the mechanical portion of the switch as well.
If your battery has gone flat or required a change, you may experience this issue. This can be generally solved through performing a vehicle handover using the diagnostic device. However, if the condition is not related to battery failure, then it is likely the activation of the door handle is not being seen by the window mechanism. There are a number of potential ways this can fail and it is necessary to follow a procedure to isolate the cause. Go through the functionality of the door and window in question from locking to unlocking to open close from both inside and out. Commonly, this will narrow down the problem to a micro switch in the door handle or lock mechanism.
This problem is most prevalent in Boxster models but can show up in the coupes as well. The first module to check is located under the driver seat. This is prone to water damage around the connector. In some models it can be removed without taking out the seat, but on most, seat removal is necessary to access it. When the connectors become corroded as they can with wet feet getting in the car or leaving the top down during a shower or indeed the window open during a shower, strange electrical faults can appear. Check this module first before attempting extended diagnosis on interior or non-engine electrical issues.
Over time the refrigerant from the AC system will find its way out of the hoses and joints. If, however you refill the system and sometime later the system is again low on refrigerant, there is clearly a larger than normal leak. Leaks can occur at any section joint or hose, however, one of the most common and missed places for the leak is at the lower corner of the front condensers.
Debris from leaves and road dirt can build up tucked in the extreme lower corner of the condensers on 911, Boxster and Cayman models. The debris can hold moisture and degrade the aluminum to point were a hole can appear. This is almost impossible to see or clean out without the bumper removed. The leak often goes undetected even to a sniffer without the debris being cleaned away. Check this thoroughly before making other assumptions – like an AC compressor which rarely have issues.
Very common and very annoying for the person with their head in their looking for something. The struts on either side of the hood or lid fail over time. This is annoying but also dangerous – the latch on both the hood or the engine lid can give your head a nasty blow if it falls down unannounced. Replacing the struts is simple and they are available online at low cost. You’ll have a better relationship with the shop that works on your car if you fix these!
All of the cabriolet tops experience issues at one time or another. These vary from the degrading of the rear window to the unbalanced or lopsided opening and closing. The window is easy – a good automotive upholstery or top center can replace that old tired plastic rear window very economically. The other issues with the top that concern opening and closing usually have a simple cause – first, the older Porsche 911 and Boxster had a revised set of motors and drives to cure the most common problems. Usually this means you have to replace the entire drive system as the newer versions are not compatible with the older components. Secondly, the bushings on some of the support arms fail and this causes the lopsided effect. This is a relatively inexpensive fix.
On storage – don’t store the car with the top down. The top tends to shrink and after a few years will not stretch enough to reach the close position. Always store the car with the top up.
Many of the older 911 and Boxster models are starting to experience failure of their catalytic converters and mufflers. In many cases, the pipe leading to the cat on a Boxster will crack and fail completely. Initially, you’ll start to notice a rattle back there. This is caused by the muffler or the cat or both coming apart internally. While annoying, it’s also potentially destructive – a partial blockage in the exhaust can cause the engine to not run or worse it will build heat at the blockage point. Seeing a catalytic converter glowing bright orange under the bumper of a Boxster is quite disconcerting! This has car fire written all over it!
The replacement parts from Porsche fall into two categories – 1. ridiculously expensive or 2. not available. The solution is an aftermarket exhaust that fits your budget. See our product sections for some sensible suggestions to replace the cat or muffler sections.
In some regions, such as the midwest, cars are often stored over the winter and not driven much until all that nasty snow stuff disappears. The fact that you have a warm, clean and perfect garage does not mean you’re alone! Our small rodent friends that we share this planet with are seeking out the exact environment you have created and they are experts at finding a safe place and hiding beyond your view.
The cabin air filter makes the perfect place for a warm nest – when was the last time you looked in there? Also, the center of the engine, right below the intake, is a perfect place for the safe consumption of food. It’s supplemented by wires that are coated with a plastic made from corn and on cold, long dark winter nights when food is in short supply, that wire seems pretty tasty.
Of course, you are blissfully unaware of all of this until the car displays strange engine faults and a musky odor from the air vents! On one occasion, we removed a whole mouse family from a 911 cabriolet that had eaten the wiring harness, destroyed the carpets, (top stored down) and had eaten most of the cabriolet top. The lady owner described rough engine running, an alarm that sounded for no reason and an odd smell while she drove it to us with the top down! The funniest moment came when the tech inspecting the car was confronted by at least 10 mice that scattered in all directions – funny how a grown man can be so spooked by mice running in all directions!
Take rodent precautions even if you are certain you don’t have that problem.
The flat 6 engines from Porsche have variable valve lift and timing. The variance is controlled by the cam solenoids located in the valve covers. Problems with these solenoids are often the cause of a CEL – engine management should provide codes which identify the solenoids that are failing and replacing them usually solves the problem. Some can be replaced without the removal of the valve cover; however, others do require the valve cover removal and are more intense work. We recommend inspection of the wiring to the solenoids before replacing them – these can be corroded on older cars due to their location.
This is a problem that so-called experts will tell you doesn’t exist. However, we have diagnosed and fixed this issue many times.
The engine runs perfectly below 3K RPM. Above 4K a misfire is reported on a single cylinder and engine management shuts off the cylinder – now, below 3K RPM the engine runs rough until the fault is cleared – then it runs perfectly again below 4K until the fault is triggered again. Typically, this happens to a single cylinder repeatedly. Initially, this sounds like a failing spark plug or coil and can indeed be solved by replacing them, if you’re lucky. However, if you have replaced both the coil and the plug and still have the same problem, there is another solution.
The Porsche flat 6 engine (in particular the M96) has a two-stage intake lifter. As you accelerate, the lifter expands to increase valve lift. The lifter commonly breaks and during the second stage of valve lift, which occurs above 4k rpm, it does not function correctly – this results in a misfire. The engine management then shuts off the cylinder until the fault is cleared.
This can be solved by replacing the lifters on the particular cylinder on which the fault occurs – although replacing all the lifters on that particular bank is probably the recommended solution. If left alone, the lifter can stick causing a permanent misfire or worse – in a couple of cases we have seen, the stuck lifter broke the intake camshaft destroying the bearings in the valve cover. We also experience a Boxster engine where the lifter had been ejected out of the valve cover, leaving a nicely sized hole and very oily mess. In both cases the engines were repaired and functioned perfectly afterwards.
Under the worst circumstances, this can look like peanut butter in the coolant reservoir but starts as an oily film. There are many potential problems associated with this sign – oil could be getting in to the coolant from a blown head gasket, from a crack in the cylinder head, a crack in a cylinder liner or the oil cooler. For sure, coolant in the oil is a bad sign, the question is how lucky will you be as to where the problem is.
The simplest place to start is to replace the oil cooler – this is the easiest and least expensive item to tick off the list of work needed. If you need to go to the next stage, having a new oil cooler is not the end of the world and at least eliminates the cooler as the source immediately.
If replacing the cooler does not solve the problem, the remaining options are expensive and require major engine surgery.
In general, these cars are pretty reliable for their cooling systems. There are however, a number of weaker areas that can cause issues. One of the most frustrating is a small crack in the coolant reservoir. This happens on all these models and usually shows up as a coolant smell while driving and minor loss of coolant over a period of time. Eventually a minor crack will split wide open and empty the reservoir rapidly – this is to be avoided if at all possible. Replacing the reservoirs on these models is not expensive but can be a pain – look at the location of the reservoir on a 996 and notice you need to extract a fairly large object through a very small space. You should never loose coolant – so if your coolant level declines, find the cause and solve it asap.
On these models in particular, the radiators are low down and exposed to debris. Small holes in the radiator can be difficult to see without removing the front bumper and searching for the telltale white coolant stain. Often the holes are not caused by debris hitting the radiator but are due to deuteriation of the seals in the corners. Leaf and road debris is not easily cleaned out from the depths below the bumper and can hold moisture against the radiator and cause metal failure. We recommend cleaning regularly or adding screens to the front of the openings – see our product sections for the solution.
The newer models have the push click lock type of hose connector – no clamps. These are easy to get on and off but have a nasty habit of being one-time use. If you have to remove a hose with this type of connector ensure that when replaced it does not leak under extreme pressure. Of course, if it does, you need to replace the complete hose and not just the connector.
Water Pump Failure
Water pumps fail regularly. This is not news but solutions have been over hyped. The bearing in the pump supporting the shaft wears and the shaft starts to wobble. This develops into a knocking noise sometimes accompanied by a coolant leak. The hype – get rid of the plastic impellor and put in a metal one – seems a solid idea, right up to the point where the bearing fails again. Now the metal impellor will wobble and score the inside of the block causing permanent damage. Now metal flakes are floating around the coolant system. In some cases, the damage is so severe that the case half need to be replaced.
We recommend sticking with the plastic impellor and inspecting the pump on a regular basis. It’s easy to see when the engine is running and you just have to watch for wobble.
A crack in the cylinder liner of the flat 6 can show up in a number of ways from coolant consumption, loss of compression to oil consumption – here’s a favorite story. Customer tows a 997 to us. A coolant hose had exploded – one of the main pipes leading to the radiators. Customers says the car didn’t over-heat, the hose just exploded. Replaced the hose, refilled the coolant, test drove the car for 30 mins – everything was perfect.
Customer calls the day after picking up and driving 1-hour home – car flashes low coolant – all the coolant disappeared from the reservoir. Of course, customer blames us for not putting enough coolant in the engine, LOL. Car is towed back.
Scanned the car – no overheating and no faults or events. We refilled the coolant, ran the engine and drove the car – it’s perfect. Where did that coolant go? We decided to let the engine run while we watched and ate lunch. The engine ran perfectly for approx 55 mins, then all of a sudden it rapidly started to get hot, a coolant burning smell appeared in the exhaust and the coolant level started to drop. Once it had cooled down, we could repeat this perfectly – every 55 mins of running and it would overheat and consume the coolant.
Long story shortened – once we had dissembled the engine, we found a series of micro fractures in the cylinder linings. It took nearly an hour of running for these cracks to open enough for the engine to start consuming the coolant. Engine required a full rebuild and liner replacement. Cracks can turn into chunks blown out of the liners as well.