The Porsche brand is synonymous with reliability and durability, but its cars do require periodic maintenance and repair. In my line of work at an independent Porsche repair shop with decades of experience on all Porsche models from the 1950s 356 to the latest 911 and Panamera variants, I have seen all kinds of strange issues over the years. However, there are a number of pattern failures and typical problems that we look out for whenever inspecting a car. The following will describe five of the most common issues that we encounter with customer Porsches, in no particular order.
1) “Check Engine” Light
Perhaps the most common across-the-board issue with modern Porsches is the “check engine” light (CEL). The CEL is the indicator light for the on-board diagnostic (OBD) system of the engine control unit (or DME for “digital motor electronics” in Porsche-speak). Early, OBD-I systems (late 1980s-1995) were only capable of monitoring basic DME and engine sensor functions, and would only store fault codes and illuminate the CEL in the case of a complete sensor failure or an open or short circuit in the DME or a sensor wiring circuit.
For the 1996 model year, the United States Environmental Protection Agency (EPA) mandated the implementation of OBD-II protocols for all light vehicle engine management systems. OBD-II standards stipulated that countermeasures be taken to protect the catalytic converter(s), including monitoring of catalytic converter function itself (via additional oxygen sensors) and on-board misfire detection (by monitoring crankshaft speed and crankshaft to camshaft correlation to determine which cylinder is misfiring). Additional emission control systems such as the fuel vapor recovery/evaporative emission control systems and secondary air injection system function were also required to be monitored.
Therefore, a CEL on an OBD-II-equipped car is a much more common occurrence, as anything that could potentially affect exhaust emissions will cause fault codes—this could be due to a slight vacuum leak in the intake manifold to degradation of an engine sensor to a loose gas cap! In most cases, a steady CEL without any noted change in engine running is not an emergency, but a warning to take the car to a Porsche specialist as soon as possible. A flashing CEL indicates an active cylinder misfire that could possibly cause catalytic converter damage; if this is consistent, a tow to the shop might be prudent.
Generic OBD-II fault code readers are readily available these days, but they only fully display general OBD-II fault codes—any Porsche-specific fault codes will come up as “unknown.” A Porsche-specific scan tool will provide the proper fault code description and freeze-frame data, along with live engine running data to assist the technician in diagnosing the problem. It must be said that a stored fault code does not usually point directly to a component at fault; it merely provides the technician with a clue to the general problem area. Porsche publishes troubleshooting charts for most fault codes, but many experienced technicians develop their own shortcuts to help zero in on the problem.
Once the problem is determined and the repair is made, the fault code is cleared, and a series of “short tests” can be run using the scan tool to force the OBD-II readiness monitors to run to verify the repair (these on-board monitors normally take at least two complete driving cycles under specific driving conditions). In the case of a 2010 or newer Porsche, the fault codes are “permanent” and cannot be manually cleared with the scan tool (this was mandated by the U.S. EPA in an attempt to thwart DIYers from simply clearing fault codes with generic scan tools in an attempt to bypass emissions tests). Permanent fault codes will not clear until the relevant OBD-II monitor is run, or via special procedure with a factory-level PIWIS-II (Porsche Integrated Workshop Information System II) or PIWIS-III (aka PTG III) scan tool.
2) Oil Leaks
Despite the adage that all old Porsche engines leak oil, it is possible for the underside of such an engine to be dry and drip-free! However, the amount of sealing surfaces and the great rate of thermal expansion and contraction of an air-cooled Porsche engines (along with the age of gaskets and seals of older cars) mean that there are numerous potential oil leaks, and some are easier to repair than others.
Common air-cooled 911 leaks include the lower valve cover gaskets (or warped valve covers), rocker arm shafts, oil return tube seals, camshaft oil lines, and front and rear crankshaft oil seals. The in-engine oil thermostat O-ring and the oil pressure switch can also make a mess of the rear of the engine. There are a few known 911 oil leaks that require engine disassembly to repair, including oil leaks from between the cylinders and heads due to broken cylinder head studs, a leaking crankshaft nose (#8) bearing, and 964/993 engine case through-bolt O-rings.
Water cooled Porsches are also known to leak oil. The 944/968 and 928 tend to all have similar problem areas, including the camshaft housing (or valve cover) seals and gaskets, front engine oil seals, and engine oil pan gaskets.
The infamous rear main crankshaft seal (RMS) leaks of the Boxster and 996 engines are well-documented, as is the potential intermediate shaft flange seal that leaks from the same area between the engine and the transmission. However, once these issues are addressed, the M96/M97 engines do not tend to exhibit many other oil leaks besides spark plug tube O-ring seals on earlier M96 engines.
The Cayenne and Panamera engines have also proved to be relatively oil leak-free. One issue that is becoming apparent with the second-generation (92A) Cayenne /first-gen (970) Panamera V8 and V6 engines are oil leaks from the front timing covers due to broken timing cover bolts. These engines have magnesium timing covers for weight savings, and as such use aluminum bolts to fasten the covers to the engine block (this prevents the possible electrolysis that could occur between dissimilar metals if steel bolts were used). Because aluminum fasteners can fail due to fatigue, they do sometimes break, which will cause oil leaks in the case of the Panamera and Cayenne engines. The repair is to remove the timing covers and replace all aluminum fasteners, which require a precise torque-angle procedure.
3) Dead Batteries & Starting Issues Due to Lack of Use
A Porsche is often the second (or third or fourth) vehicle in a household, and as such does not always see regular use. Among other issues, frequent periods of disuse will eventually cause the vehicle’s battery to discharge. In addition to the nominal battery drain caused by the memory circuits of on-board electronics, modern sealed-cell batteries will slowly discharge on their own, even when sitting on a shelf!
Oftentimes, a modern Porsche battery will discharge to the point of being unable to start the engine after only a month of sitting idle. The long-term solution to this is to either drive the car more frequently (which means a proper, lengthy drive) and/or to install an “intelligent” battery trickle charger/maintainer (assuming that your Porsche hibernates within a reasonable distance of an electrical outlet).
Failure to perform either of the above will result in a frequently dead battery which shortens battery life and increases the possibility of the need for jump starting, which is not recommended except in emergency situations due to the possibility of a voltage spike damaging sensitive electronic control modules. A chronically discharged battery also places undue strain on the alternator, as it then needs to work overtime to charge the battery.
Beginning with the first-gen (9PA) Cayenne and 987/997 model sports cars, complete battery discharge or disconnection means that in addition to engine management system adaptation values being lost, the Porsche Stability Management (PSM) system will not function properly until the steering angle sensor is re-calibrated.
The electrical complexity of the recent generation of Porsche body control systems (beginning with the 970 Panamera of 2010, 92A Cayenne of 2011 and 981/991 sports cars) require special absorbed glass mat (AGM) batteries, which in turn require a special charging system strategy that changes as the battery ages. Therefore, AGM battery replacement must be coupled with “registering” the battery replacement with a factory-level scan tool, or battery life will be severely shortened.
4) Noises (Squeaks, Rattles, etc.)
Customer complaints of abnormal noises emanating from their vehicles are quite common, but they represent perhaps the most insidious issue that we deal with at my shop. Squeaks, squeals, rattles, clunks, and other noises can be either minor annoyances or a sign of something worse to come. When diagnosing a noise, half of the battle is duplicating the symptom in the first place. Then, it is a matter of making sure that the noise we are hearing is indeed the one that the customer is complaining about. On more than one occasion, we have heard a noise from something like the engine or belt drive, while the noise that the customer was concerned was a rattle from the car’s interior; this is why a test drive with the customer is important!
Anomalous noises from the engine are sometimes difficult to pinpoint and often take a trained ear to distinguish from “normal” noises, especially amongst the cacophonous din of an air-cooled 911 engine. For example, the tapping noise of a valve with too much clearance may sound similar to the more serious slapping of a loose timing chain (due to a failing chain tensioner and/or worn chain sprockets). Also, the flutter of a loose fan belt can mimic a much more serious knocking noise within the engine! Therefore, it pays to seek out a knowledgeable Porsche mechanic if you are in doubt about a strange noise emanating from your machine!
Modern Porsches have more complex serpentine belt drives for various accessories, which can be the source of squeaking/squealing noises, along with growling noises from the accessory or pulley bearings. If such a noise is suspected, the technician will use either a mechanic’s stethoscope or simply an ear to a long screwdriver to listen to each of the pulleys until the noise is isolated. A failing water pump bearing will sometimes exhibit a growling/scraping noise before completely letting go, but they can also fail without warning.
The 1995-1998 993-gen 911 and all water-cooled Porsches (except the early 924) use hydraulic valve lifters, which rely on a cushion of oil to maintain proper valve clearance. When hydraulic valve lifters “bleed down” or lose oil pressure, the excessive clearance will cause a tapping noise similar to that of loose solid lifters. Several seconds of lifter noise immediately after cold startup may be considered normal in the case of a Porsche that sits idle for long periods of time, but if the lifter noise becomes more and more frequent or does not cease after the engine oil warms up, replacement may be necessary. Collapsed hydraulic timing chain tensioners can also cause rattling on startup, which should be addressed immediately!
Chassis and suspension noises can be similarly difficult to locate, as they are often temperature-related or only occur on certain types of road surfaces. Sometimes, the source of the noise is obvious and is located after a brief inspection on a lift. Other times, in the case of a mysterious clunk, a drive-on lift may be necessary to keep the suspension loaded while the vehicle is “jounced” and inspected from underneath to isolate the noise. For particularly difficult noises, electronic listening devices known as “chassis ears” can be mounted at various points underneath the car; the technician can then test drive the car while wearing a headset and remotely switching channels between different listening devices until the noise is located.
In the case of a whirring or growling noise that changes with vehicle/wheel speed, it is sometimes difficult to differentiate between a failing wheel bearing and tire noise from uneven tread wear. However, a wheel bearing noise will increase with load (for example, a noisy right front wheel bearing will become louder when loaded during a left-hand turn), and tire noise will often change on different road surfaces (while wheel bearing noises tend to stay constant regardless of the road surface).
Interior squeaks and rattles can be the peskiest of all because—while they are not usually indicative of a serious issue—they can be incredibly annoying and difficult to locate! The method of isolation often consists of a second technician riding as a passenger to listen and place hands on affected areas until the problem area is located. A rattle from behind an interior door panel is usually simple to locate and repair, while a similar noise from the dashboard area may require much more extensive surgery to rectify!
The method of repair for many interior squeaks and rattles is often quite crude and low-tech: the Porsche aftersales service department has published an extensive list of foam and felt tapes, lubricants, sealants, and other remedies for isolating and eliminating irksome interior noises. On more than one occasion, we have removed dashboard panels from a car during a repair to find felt and foam tape liberally applied to the undersides, likely by a dealership during the warranty period!
5) Uneven Tire Wear
Uneven tire wear can occur on any Porsche, and it is usually indicative of a wheel alignment and/or suspension wear issue. The rear tires of a mid- or rear-engine Porsche often last 15,000 miles or less, because the rear tires bear the twin burdens of driving the car and carrying approximately 60 percent of the vehicle’s weight. Furthermore, the inner edges of the rear tires typically wear out first; in fact, the inner can be worn down to the cords while the outer edges of the tires still show acceptable tread depth. This often occurs unbeknownst to the owner as the inner edges of the wide rear tires of a sports car cannot be easily seen unless the car is on a lift or if you are down on your hands and knees!
The main reason for this is Porsche’s recommended wheel alignment settings for its sports cars often call for significantly more negative camber of the rear wheels than in the front (negative camber means that the top of the wheel is more tilted towards the center of the car relative to the bottom of the wheel). This ensures that when the car goes through a turn and the weight shifts to tires on the outside of the turn, the suspension compresses and allows the tire contact patch to remain perpendicular to the road surface and enhance traction in turns.
Because the end of the car with more negative camber will usually have more grip in turns, Porsche generally specifies less than a half of a degree of negative camber for the front wheels, and close to two degrees in the rear. With these conservative settings, the front end of the car will usually lose grip first in extreme cornering situations, causing the car to gently push wide of the driver’s intended path (versus the perilous alternative of the rear end snapping around). This results in safe cornering for the average driver, but can exacerbate premature wear of the inner edges of the rear tires during normal
driving, as most driving is done in a straight line, even in Porsches!
Another important wheel alignment setting is the toe, which is defined as the angle of the wheels from pointing straight ahead (when viewed from above the vehicle). Toe-in means that relative to the rear of the tire, the front of the
tire is pointed inward towards the center of the car (pigeon-toed) and toe-out means that the fronts of the tires are pointed out (duck-footed, if you will).
Porsche specifies a small amount of toe-in for stability; excessive amounts of toe in either direction can cause uneven tire wear and pulling or drifting in one direction or the other during straight line driving. Worn out and cracked rubber suspension bushings and ball joints can also cause inconsistent toe and camber change and thus uneven tire wear and unpredictable handling.
If your daily commute does not include mountain roads and race tracks, your Porsche’s tires may last longer if the wheel alignment is carefully set to the more conservative end of factory specifications. Many discount alignment and tire shops simply set the alignment so that is “in the green,” or in the ballpark of the manufacturer specs. However, these specs often have a wide range, so the settings should be carefully set to be as close from side to side as possible to guarantee even tire wear and that the vehicle tracks straight and true down the road.