By Adrian Streather – www.adrianstreather.com

Aug 2003

 This web site created by John Miles in May 2001 was the first exclusively devoted to the 964 series of Porsche 911s built between 1989 and 1994.  It not only covers the 964 series but also 964 owners and their charges from around the world.  John will happily acknowledge that this web site would not be anything like it is without the huge personal contribution of 964 owners around the world.  I am very pleased to contribute this 964 Biography.

The Porsche 911 (964 Series)

In the early years, the motoring press enthusiasm for this car was very positive and many times the 964 was proclaimed to be the best 911 ever, especially the revolutionary Carrera 4.  As time passed however, praise began to turn to criticism, some of which still exists.   One purpose and major driver behind John’s creation of this web site is to help overcome some of these myths and misconceptions of the 964.   It must also be remembered that the 964 was born into a period of great stress and uncertainty at Zuffenhausen.   Despite this over 57,000 964s were produced.

964 Timeline

What Makes a 964?

To say that the 964 was an 85% redesign of the previous Carrera 3.2 series is not truly accurate.  The 964 series was a completely new series.  The 964 Carrera 4 was the first production series normally aspirated 911 with all mechanical AWD.  It remains the first and last series Porsche with an all mechanical AWD system.  The Carrera 4 was the first 911 fitted with an ABS system.  The C4 was the first and only Porsche model to be fitted with an electronically controlled traction control system.  The Carrera 2 series was born from the Carrera 4.  All the innovations introduced on the Carrera 4 except AWD and traction control were installed into the Carrera 2.  There are some structural differences between the Carrera 2 and 4 at the front but this is due to the AWD installation only.

The 4-speed Tiptronic automatic transmission designed for the Carrera 2 was huge leap forward for Porsche.  The previous 3-speed automatic transmission used by Porsche from 1967 to 1980 was the Sportomatic.  The introduction of the Tiptronic brought with it full electronic control, pre-programmed driving characteristics software and an adaptive memory system.  The Tiptronic system can be operated in full automatic mode or manual mode. 

The fuel injection system used on all the normally aspirated 964s was a Bosch Motronic system extensively redesigned as compared to the earlier Carrera 3.2 system.  Adaptive memory and fault detection including impending failure was added.  The ability to plug a diagnostic tool into the 964 brought with it a much reduced troubleshooting time for many failures.

The 964 normally aspirated engines were fitted with a dual ignition system to improve fuel/air mixture burning efficiency to help with emission control.  The Carrera 4, all Turbo looks, RS series and the Turbos were all fitted with a hydraulic brake boost system.  The Carrera 2, RS America and Speedsters used the vacuum boost system.

A new central warning system was introduced to advise the driver of various systems failures.

The 964 was the most aerodynamic 911 ever built.  Its drag co-efficient has never been bettered.

The 964 in Competition

The years of racing from 1989 and 1994 were not exactly highlights of the Porsche racing history for the 964 series.  However they still made their mark.  A special Turbocharged 964 called the LeMans GT was entered for LeMans 1993 and 1994.  A special twin turbo version of the 964 was built and raced at Pikes Peak.  The Carrera Cup was used in many single type series around the world and the 964 RSR dominated the GT class in all the endurance racing world wide.  The Carrera RS basic and NGTs were used by club sports enthusiasts and professionals alike for racing.  Special IMSA version of the Turbo and Turbo 3.6 were produced and they raced in many different sport car series and endurance races worldwide.

How to Recognise a 964?

The easiest way to correctly identify a 964 is to check the vehicle identification number (VIN).  The VIN is a 17 digit international code.  Porsche use two versions, the ROW and the USA requirements code.  It is much easier to identify an American 964 as compared to a ROW 964.  The following brief explanation of key digits within the VIN will ensure correct identification of type and for the US version more detail can be extracted.  This is very important when trying to determine if a 964 is genuine and the model is actually manufactured by Porsche and is not an aftermarket conversion.

Digit 4

Digit 5

Digit 6

Digits 7 and 8

Digit 9 is a check number and is not important.  However for the USA this will be a 0 to 9 or a X and for the ROW will be a Z.

Digit 10 is the model year letter.

Digit 12 is the last number of the type and this will always be a 4.

Digits 13 to 17 make up the serial number.  Digit 13 also provides version identification but can only be used for a specific model year.  The numbers were changed around so a 5 in 1989 may not be the same as a 5 in 1994.

The use of this data is extremely important especially if the 964 being offered is not contained in the list of models found in the timeline section.  A number of turbocharged cabriolets are being claimed as factory produced.  Their VINs do not support this claim apart from the fact that such a model does not appear in the records of Porsche production for the 964.

Another issue which causes identification problems is the chassis number.  This is found on a plate directly below the fuel tank in the luggage compartment.  This number will always start WP0ZZZ regardless of version.  The important point is that the last five digits of the chassis number match the serial number of the VIN.

964s can also be identified by type number.  The type number is located on the identification label found on the underside of the luggage compartment lid and a copy of this label is found in the original service record book provided with every 964 upon original delivery.

Myths and Legends

As with any automobile model the 964 has its fair share of myths and legends.  Ask many alleged experts and they will you that the 964 is riddled with faults and is expensive to maintain.  This is simply not true.  There were only a few problems (far less than many other automobiles then and now) which were quickly rectified by Porsche which affected the 964 series.

Engine Oil Leak

In fact this was an acknowledged design flaw by Porsche.  The cylinder heads were mounted without a head gasket.  Unfortunately the engine ran a little hotter than predicted and this caused a slight warp at the base of the cylinder head and oil would weep out.  This problem was rectified by the installation of a head gasket during the engine production of model year 1991.  A fix was also approved for the earlier engines.  The main problem is that the owners of the time did not have this fix carried out.  Some of the 964s now weep oil.  The problem is fixable.  A caveat has to be added as well regarding oil leaks.  This introduction is being written in 2003 about engine produced from 1988 to 1993.  The Porsche engine is an internal combustion engine and is dry sumped.  All internal combustion engines develop oil leaks with age.  Not with mileage but with age.  Gaskets and seals eventually fail.  The less the engine is used the more likely they will fail in a shorter calendar time.  This is not a model or 964 problem this is just reality.

Double Mass Flywheel

The second most discussed problem is the double mass flywheel problem.  This problem does not affect the following models;

The DMF was introduced in model year 1990 to meet stringent new internal noise level regulations.  The DMF consists of two flywheels mounted together with the starter ring sandwiched between the two masses.  The problem was with the early DMFs was that one mass would move too far.  This made the assembly make strange noises.  A very distinctive “clunk” sound could be heard along with vibrations in the transmission.  If the problem was not rectified gear changing problems would occur and the myth of clutch reliability arose.  This is dealt with later.  Porsche quickly came up with fixes for these problems.  For the Carrera 4 a new secondary flywheel mass (the turbo version) was used and for the Carrera 2 an alternative supplier was found for the DMF.  LUK was the name of the new supplier.  Porsche 356 owners will be familiar with the name LUK.

Once the early DMFs are all replaced this problem will disappear forever.

Dual Ignition System

The last problem related to the dual ignition system of the normally aspirated 964 M64 series engines.  The turbo charged engines only use a single distributor system.  The second or secondary distributor drive is a belt drive from the engine driven primary distributor.  This belt is made from synthetic rubber and it failed quickly under the effect of Ozone created by the spark inside the distributor caps.  Porsche fixed this problem quickly as well.  A vent kit was introduced to remove the ozone from the assembly.  It is a simple modification it works yet many 964s even in 2003 do not have this vent kit installed.  However please remember that even with the vent kit installed the belt will still age and eventually fail.  It is no different to a rubber cam or timing belt used on other Porsches.  Rubber belts should be replaced every 100, 000 km (60, 000 miles) or every 5 years whichever comes first.  In a very worst situation a broken secondary drive belt can cause expensive damage to the engine.

Clutch

The clutch plate used by Porsche in the 1989 Carrera 4s only was rubber centred. When the double mass flywheel was introduced there was no further need for a damped clutch plate because the DMF was now the damper. The clutch plate used in conjunction with a DMF is known as a solid centre clutch plate. It has no springs or any other damper device installed. The only thing that can wear out is the lining and this is a consumable or expendable product that eventually wears out.  The life of the clutch is highly dependent upon the drivers foot co-ordination and how fast the clutch is let out.  A failed DMF can accelerate clutch plate wear.

Rear Blower Fan Resistor

Ensure the rear blower fan ballast resistor (speed limiting device) is replaced with the newer version which contains overheat protection. If the new ballast resistor is not installed there is a risk of an engine bay fire if there is a specific sequence of events that occur. Engine turned off whilst very hot and the air temperature in the rear blower fan plumbing is above 95C. Fan bearings failed and rear blower motor is seized. A very rare but easily avoidable potential problem. Inspecting of this resistor should be part of any pre-purchase inspection.

Summary

All Porsches can be expensive to maintain simply because parts costs are generally higher than your average automobile. Labour costs are higher due to access issues especially in and around the engine bay. The 964 is a true sports car, a Porsche and maintenance costs are higher. The 964 is a high performance car and reliability is always going to be less as compared to a daily plodder. The 964 likes being driven so drive it often. Lack of use can be more damaging than too much.

My own personal Carrera 4, a 1989 model has never broken down and left me stranded. Yes it has had the odd failure but never one that made it undriveable. The 964 in the Porsche world represents excellent value for money, is extremely powerful and a lot of fun to own and drive.

Adrian Streather
Switzerland - Aug 2003