What You Need to Know Before Buying A Used 911 Carrera 991
If your just taking the initial steps to buying a Porsche 911 Carrera 991, this guide will highlight some of the technical issues to be aware of before you commit to buy.
The 911 Carrera 991 was launched in 2012 model year and production of the 991 generation only recently ended on December 20, 2019. With more than 233,00 units produced over a seven year period, there are some excellent bargains to be had, in what was the seventh generation of the 50 year development of the 911.
The 991 replaced the former 997 with sleeker looks and the appearance of being a larger car, although the actual increase in size was approx 56mm. The real difference came in the build quality and the options available. Essentially there are three models – the Carrera, Carrera S and the GTS. Each model is available in either 2 wheel or 4 wheel drive with a matching coupe or cabriolet body option. In addition, each model has the option of a seven speed manual transmission or a six speed PDK auto trans.
The original 991 was powered by an all new design engine – 3.4L flat 6 for the Carrera and 3.8L for the S models. The introduction of the Turbo models in 2013 brought a twin turbo charged 3.8L flat six making up to 552HP. In 2016, Porsche launched the 991.2 update to the the 911 with a revised all turbo line-up. The 991.2 Carrera now featuring a twin turbo 3.0L engine and the Turbo S model jumping to 572HP.
Other derivatives in the 991.2 range included the 500HP GT3 in Sport or Touring mode, the Carrera T and the 700HP GT2.
991 Enters Value For Money Territory
As deliveries of the new 992 increase the price of the 991 will naturally decrease over the next 12 months. The later 991 will have to find a place in the market below the new car value to make it an attractive enough proposition. If the previous change from 997 to 991 is to be any guide, over the next twelve months the 991 should be at it’s best value for money price.
The first step, once you’ve identified a used 991 candidate, is to get a thorough inspection by a local expert. The pre-purchase inspection is designed to identify mechanical problems that may not be clearly evident at first glance. The 991 is an extremely reliable car and does not have the issues associated with the 996 or early 997. Getting a repair history on the car, if available, is helpful and will instantly identify or eliminate potential problem areas.
The number of owners doesn’t necessarily matter with a Porsche – the work and records performed do. Many owners are enthusiasts and will keep all the invoices from service or repairs performed. A great place to identify an enthusiast car is at the PCA Mart.
If a seller wont let you inspect the car, walk away.
Consider who is selling the car. For a private sale you need to know why the vehicle is for sale. If you’re buying from a used car dealer, do your research to learn where the dealer got the car. If it’s a dealer that specializes in Porsche, well and good. We list some excellent third parties companies who specialize in late model and vintage Porsche. Many of the late cars will end up as CPO cars at the dealer.
Potential Issues To Be On The Look Out For
Mileage and Service History
On cars approaching 8 years old mileage should be approaching 80K. In fact, a 991 Carrera with 80K miles could be in a better condition than one that has an attractively low mileage reading. Low mileage cars can have hidden issues and, while save for a few states, the 991 isn’t a daily driver. 10,000 per year would be considered on the higher end mileage at this stage but might represent the best value.
Service intervals on the 991 were switch to 2 years or 20K miles. This is over generous in most peoples opinion and could well lead to a low mileage car missing most of the service intervals. You’ll want to take a good look through any documented history available. A clear pattern of servicing on higher mileage cars is essential, but on low mileage cars timed intervals between service is the key thing to look for regardless of mileage. Every 12 months would be good practice.
Fault Codes, Events and Over-revs
Before buying a 911 991, it is essential to know when the last time the system fault codes were cleared and to check the status of the emission monitors. It’s not difficult for a seller to clear the faults just before you arrive for a test drive. Clearing the engine faults also resets the emissions system to a state of “not ready.” Emission readiness tests often occur over multiple drive cycles. So, after a reset, faults may not return for a significant number of miles. Again, this is easy for a competent repair shop to check or indeed the DIYer using a handheld scanner.
It is essential to determining the health of the engine to be able to read this data.
How Hard Has The Car Been Driven?
Taking the engine to the red line for RPM is a good thing, but going over the red line obviously can cause damage. A gear change at red line will actually cause the revs to increase slightly momentarily – nothing bad here. But, if you select the wrong gear, the engine revs to go way over the red line. This is the famous “miss-shift” that has caused many engine explosions.
Porsche engine management records many things – one of the most significant is an over-rev situation. Data is permanently stored within the ECU showing running hours and when engine events have occurred. There are six levels of over-revs recorded ranging from the engine being red-lined through to what would be a potentially catastrophically high RPM event. Events in the first category suggests the car has been properly exercised, but events in the higher categories could be hiding a potential life shortening engine situation.
Many Porsche owners like to go to track days. On the track, gear changes will occur right around the rpm maximum red line. These events will be recorded if they reach the lower levels of the over rev counter. Multiple recorded events in the lower over-rev categories could be a sign of how much track time the car has experienced.
Front Radiators and Air-conditioning Condensers
The design of the 991 has the placement of the coolant radiators and air-conditioning condensers low down in the front bumper. The position and open vent nature of the design leaves them not only susceptible to stone impacts, but also to the buildup of debris and dirt stuck close to the radiators.
These front ducts and debris need to be cleaned out regularly or protected by an aftermarket screen. The front bumper has to be removed to reach the radiators and most owners never do it as part of regular service. The 991 will commonly have a failure of one of the cooling fans due to a build up of debris that destroys the fans bearings.
Take a flash light and look closely to see whether the front air intakes are full of rotting leaves and debris when you inspect the 991. Look closely, the debris will be around the sides of the radiators.
Damaged or corroded radiators and AC condensers cannot be repaired and must be replaced. Expect to have to replace a cooling fan without the addition of the aftermarket screens.
The brakes on the 991 are excellent. Brake pad material does degrade over time, so on low mileage examples check to see when the last brake service was performed. The brake fluid should be changed every few years regardless of mileage.
A complete brake service with pads, rotors and sensors can be quite expensive. So, if you’re buying from a used car vendor, look for new pads on old rotors. Both the pads and rotors should always be changed at the same time. There should be a wear lip on the rotor and the size of that lip will determine how much mileage remains. Worn rotors crack or disintegrate, which can be particularly unpleasant when driving!
The 991 came with drilled rotors. Look carefully to see how clear the holes are and make sure there are not cracks between the drill holes. Cracks between the drill holes can lead to a much bigger crack and rotor failure very quickly under heavy braking.
Porsche Ceramic Composite Brakes
The ceramic brake setup was a factory fitted option for the 991 and generally seen on the S, Turbo and GT models. Porsche Ceramic Composite Brakes (PCCB) use cross-drilled, carbon fiber reinforced ceramic discs with special composite pads. They produce amazing stopping power and are 50% lighter than a standard brake a setup. They also have a considerably longer life than their standard counterparts. However, the expected life of the PCC brakes does not always play out in reality.
If you are buying a Porsche 911 991 that has the PCCB option, it’s worth being certain how much life remains on the brakes. Parts for the front brakes alone could run you more than $10,000. Sounds like a good reason for trading-in a car!
Change Over Valve Campaign
Most recently, the 991 cars have had all of their COV solenoids replaced in a maintenance campaign. Check to see if the car you are looking at has completed that campaign.
The COV device is designed to direct vacuum to effect a change when requested to by an electrical control unit e.g. open a vent, change the position of an exhaust flap, redirect hot air from feet to screen etc. Likely systems affected on the 991 include:
1. Air Cleaner Flap
2. Acoustic Simulator
3. Heater Shut-Off Valve
4. Exhaust Flaps
5. Coolant Shut-Off Valve on Engine Bypass Circuit
6. Tuning Flaps
7. Shut-Off Valve on Heat Exchanger for Gear Wheel Set Oil
8. Shut-Off Valve for Clutch Fluid Heat Exchanger (PDK ONLY)
9. Fuel Tank Vent Valve
Value For Money
Let’s face it, justifying the purchase of a Porsche 911 991 to your other half using value for money is fraught with difficulty! However, with the arrival of the new 992 car, 991 prices will drop sharply over the next 12 months. The 991 is an excellent car that can be driven daily and yet performs outstandingly on the track. Gone are many of the issues of the past and in general the 991 is reliable and fun to drive.