ENGINE AND GEARBOX
The 996 GT3 is powered by a 3.6-litre drysumped flat-six with motorsport pedigree — the unit can trace its roots to the 911 GT1 and 962 race cars, lineage which helps to explain the mix of old and modern technology, such as a late air-cooled 911 crankcase paired with two cylinder heads (as opposed to six) and water cooling. Accompanying the classic crankcase is a gearbox with a design also 'lovingly borrowed' from the air-cooled era. "Though these engines have a great reputation for being very reliable, even the newest 996 GT3 is closing in on its twentieth birthday," Chris points out. "You should look closely for signs of oil and water leaks."
He cites the external coolant pipes running around the outside of the engine as prime suspects for the drips you might find on your driveway. "A common complaint can be found where coolant pipes attach to the engine. They are slip-fit and held in place by a form of epoxy glue, which was intended to hold pipe collars in their housings and create a seal, but over time and through repeated heat cycles, this adhesive breaks down, causing the pipes to work free and a sudden loss of coolant, which could be catastrophic for the car's engine. More importantly, it could also be very dangerous if the coolant pours out onto a busy circuit."
Enthusiastic Diyers may have "bodged" the fix by pinning the pipes in place. "It's fairly easy to drill through the cast housing, into the coolant pipe and then 'pin' the two together with a bolt secured with threadlock," Chris continues. "This prevents the pipe from working its way free, but it isn't the proper way to correct the problem. Ideally, the engine should be removed, the cast housings should be taken off and all affected parts should be thoroughly cleaned free of old adhesive. After this process, the coolant pipes can be Tig-welded to their respective cast housings, providing a thorough seal which will last the life of the engine. Extended rubber or silicone hoses can be used during reassembly."
Considering only a hundred right-hand drive 996 GT3S were originally allocated to the UK market, Chris is proud to say PIE Performance takes care of nine surviving examples of this trailblazing 911. "They're great cars," he smiles. "The noise of the Mezger engine is intoxicating. Someone new to the 996 GT3 might think the model sounds a tad 'agricultural' on idle, but they'll change their mind when at the track and climbing quickly through the upper rev range and on toward the redline. The noise is astonishing and extremely addictive!"
As we've reported in previous issues of 911 & Porsche World, radiator corrosion can be a problem on all 996s. The GT3 is no exception. The coolant radiators are housed behind the front bumper (along with the optional airconditioning system's condenser) and are susceptible to stone chips and corrosion resulting from dirt, salt and leaves coming in through the bumper air scoops. Sadly, many 996 owners don't bother vacuuming these areas, allowing dirt and rotting leaves to fester, leaving plenty of time for damage to develop between servicing. Suspect radiators and/or condensers will need to be replaced to avoid overheating or the loss of air-conditioning.
Original GT3 gearboxes featured phosphor bronze synchromesh rings, which were updated to steel parts for the facelift 996 GT3 in 2003. Some owners retrofit the later parts to early cars. Limited-slip differentials are known to wear prematurely due to being configured with lowlevel preload, while clutches can feel heavy on GT3S used primarily as road cars. Replacement parts are expensive, but easy to come by.
"For 996 GT3S used in anger at the track," Chris continues, "I recommend frequent gearbox oil changes. Renewing fluids is a cheap job which will help to achieve a long service life."