Porsche 996 newbie guide- Good tips to know straight away.

So you've just bought a 996 or your thinking about buying one and your in the process of getting to know the car. Congratulations on your decision.

This page is intended to make you aware of a couple of things that are worth knowing so that you can avoid having some of those "oh shit"  moments when something doesn't seem right.

I am writing this from the perspective of having owned a 2002 C2 Tiptronic 3.6 with 108,000 miles on it and more recently a 1999 C2 6speed with 68,000 miles here in the UK. 2010.

Cooling Issues.

996's (early ones in particular) do seem to show higher than 'comfortable' temperatures on the gauge .. ie needle in the right half of the gauge when in stop-go traffic. This is relatively normal in such conditions. Driving in the  UK through a full year my cars typically had the needle over the zero in 80 most of the time but in stop go traffic the the temp would creep towards the right giving you that "it's going to overheat feeling". They don't though and it does take quite a long time to get the temperature back down.

Now there are some coolant system issues that should be addressed or which are worth knowing about though.

Intake muck The 996 can collect a bunch of leaves and rubbish in the left and right radiator openings in the front bumper and this can do 2 things. It can make your car run hot due to obstruction and it can lead to some corrosion in the radiators. So - get a vacuum and suck out all that rubbish for starters. If you can smell coolant in that area then you may have some seepage from a corroded radiator and may be up for a radiator replacement (or 2). However lots of owners find that their cars run considerably cooler after cleaning out the radiator area. Taking off the bumper to do  the job properly is also worthwhile (check you tube or rennlist for front bumper removal how to guides)  Front bumper & radiator cleaning video (Youtube).

Coolant Cap The coolant cap was re-designed a couple of times because it leaked. If the part number on the coolant cap ends in 00 or 01 it is one of those that developed leaks and so a replacement from the dealer would be a good investment for avoiding trouble.

Coolant expansion tank Likewise early models of the coolant tank itself occasionally developed hairline cracks which were reportedly able to leak, sometimes in an obvious fashion and sometimes not so obvious. However the main thing with the coolant tank is that it's design led to drivers getting a flashing coolant light (falsely suggesting low coolant) when accelerating hard. I experienced this only after doing a sharp U-turn followed by hard acceleration. The tank was redesigned to eliminate this issue. I haven't replaced my tank as it is an infrequent occurrence.

Occasionally other items may be the culprit like a water pump developing a leak but this is less common. It seems that these leaks can often be smelled before they are as obvious as a dripping/hissing leak. I also notice that the Technical Service Bulletins advise that in the event of a coolant hose not being able to have adequate sealing from the clamping force of the spring style clamps, then the offending spring clamp should be replaced with a more traditional worm drive hose clamp. Having said that I am surprised to see just how well the spring clamps on my cars have held up.

Air Oil Separator (AOS)

This is a plastic component on the upper forward left side of the engine which as it's name implies is designed to separate oil vapours from crank case air. When it fails the car will produce alarming amounts of smoke - for a short period of time after starting the engine. Now this smokey condition only tends to occur after  the car has been driven hard and is exacerbated by having a high oil level. The smoke comes from excess oil being drawn into the intake and burnt, it's not harmful but it is unsightly. Some people have managed to replace the AOS with the engine still in the car but it's not an easy job. Here's how one Rennlister did it AOS Link . There can also be a minor oil leak in the RMS area if not installed properly.

Fuel Gauge Level.  My 02 996 occasionally showed an incorrect fuel level after filling the tank from a near empty condition. This is related to some binding that occurs with the fuel level sensor in the fuel tank. Porsche developed a fix for it. However the problem corrects itself after a while. See TSB

Intermediate Shaft Bearing Failure (IMS failure)

This is a much debated topic in the 996 world with a great deal of fear / fear mongering associated with the subject. The intermediate shaft is an internal engine rotating shaft which has an enclosed bearing at one end. The bearing can fail with no warning leading to catastrophic engine failure. It doesn't happen very often. It happens to engines with all sorts of mileage (low & high), it occurs in Boxster engines and early 997 engines as well. The actual number of failures is probably quite small but because the consequence is that a replacement engine is needed, there is widespread debate on the issue. My personal view is that it is a risk that needs to be dealt with according to your own budget and degree of risk tolerance. It should absolutely not put someone off buying a 996. In my own case I had a 108,000mi 02 Carrera 2 which was covered by a mechanical warranty so I wasn't worried about it. I drove the car the way it was meant to be driven. I didn't thrash it, but I also didn't let the high mileage or IMS fear put me off taking it to the track a couple of times either. That was a very strong and smooth engine for the entire year that I owned it. My 99 68,000mi Carrera 2 doesn't have a warranty and I plan on keeping it for a long time, so with that car I will replace the IMS bearing with an aftermarket version which has been developed. I will also monitor how well this aftermarket version is performing and I will consider replacing it every few years if the history begins to show that it suffers from any significant kind of wear like the OEM part. In other words I will treat the IMS bearing as a service item if needs be. The IMS is only accessible when the transmission and flywheel is off the car, so labour wise it's like getting a clutch done. There is no end of discussion on this topic on the Rennlist 996 forum.

Rear Main Seal (RMS)

The rear main seal is the rear crank shaft seal, it sometimes leaks and sometimes doesn't. Porsche redesigned it a few times. As you can see from the pic, a leaking RMS or IMS is going to show as an oil leak at the junction of the transmission and engine. If it's the RMS that's leaking it is not the end of the world. If it's the IMS that's leaking that could be indicative of IMS issues.

Dual Mass Flywheel (DMF)

I wouldn't rate this as a particular issue to be honest, I just mention it here for completeness. Porsche uses a dual mass flywheel on the 996, that means it's like two plates connected together by a spring mechanism which absorbs some engine vibration and shock as the clutch is operated. It seems to be a commonly held view that the DMF isn't lasting 100k like expected so may need replacing earlier than that. Some workshops I spoke to suggested that a new DMF may be required when a clutch job is done. I will test it myself when I do my IMS bearing.

Idle quality

Some owners find they have idle quality issues or even check engine - error codes - these  may be readily addressed using the information in these throttle body cleaning DIY guides. Link 1  Link 2

Fuel - Octane rating

The 996 is tuned to run on 98 Octane fuel. You can safely run it on 95 Octane fuel however the ECU will detect the increased knock (pinging / detonation) that will happen under heavy load and it will retard the timing to counter the knock when it occurs. By retarding the timing the ECU will cause the engine to have (slightly) reduced power. Running 98 Octane fuel means that the standard ignition mapping will be well matched to the fuels octane rating and incidence of knock will be minimised, the ECU will not have to retard the ignition timing and suffer a power loss.

Useful Information - Get smart

There is a lot of useful documentation available online including the Porsche workshop manuals in pdf form - includes electrical diagrams. These show how to do a lot of things, there are also Porsche Technical Service Bulletins (TSB) available online which show updated procedures and specific fixes in addition to the workshop manuals. The Porsche parts software application PET can also be downloaded and installed - its a bit clunky but it has tons of useful information - especially exploded diagrams showing you parts in various assemblies and part numbers (may not be the most current numbers though). Links to these docs are on my main 996 'Emmy' page. Other web sites like Pelican Parts show picture by picture engine teardowns which are very insightful by identifying various parts. You can even look up the prices in US dollars for porsche part numbers at the renntech web site - handy when trying to estimate what your costs may be for a certain job.

Clutch feel & stalling

I've been driving my 996 for a month or two and I had noticed that I come close to stalling the car quite regularly when going over a particular massive speed bump or manoeuvering into parking spaces. Now I have discovered that lots of 996 owners who are quite familiar with driving manual cars also experience this issue with the 996. It turns out there is a helper spring attached to the clutch pedal which serves to make the pedal operation very light but at the same time it makes it a lot harder to feel the point of engagement of the clutch. Removing the spring increases the pressure required to operate the clutch but gives you the feel you'd expect. Details here - Rennlist clutch pedal thread

Jacking

Jacking the car from the jack point just forward of the rear wheel arch will lift the entire side of the car. However with the jack in that position you can't put an axle stand there - as may be your wish if you want to have the car up on 4 axle stands. In that case I place the axle stand as per the attached pic. The original guide I found for jacking a 996 advised jacking the rear of the car from a point on the engine, personally I don't like to do it that way and I have read posts from owners who tried that method and found that their fluid filled engine mounts burst when they jacked the rear up from the engine. Once the car is raised It's also possible to re-locate the jack in the location where the jack stand is in the following pic, and then re-position the jack stand back to the position in front of the rear wheel arch. As always with jacking, do it incrementally and keep checking that the jack stands haven't moved to a point where they can slip at the point where they are contacting the car.

Pre-purchase Inspection

Here is what I consider to be basic stuff to look for when buying. I wouldn't be afraid to buy a high mileage car that has been well maintained as evidenced by good running and appearance and a paper trail to back it up. Just be conscious that more components may need to be replaced, but then again some big ticket items may have already been replaced.

Check the coolant, is it clean (free of oil)?, Is the level correct?

Is there any coolant smell after a drive - in vicinity of radiators, and engine?

Check the oil on the dipstick, does it look clean/fresh?, is the level correct?

Check the oil filler neck - should be dry and free of oil/water mix that looks like cream.

Does the engine smoke on start up?

Does the engine idle smoothly & quietly?

Look underneath the engine, does it leak oil near the junction of the transmission & engine?

Check the condition of the mufflers for rust at the seams.

Does the clutch feel smooth / light?

Are there unusual noises whilst operating the clutch?

Can each gear be selected smoothly?

Does the car drive straight & true (alignment)

Is the tyre wear even on all tyres ? (good alignment)

Is the steering wheel free of vibrations at speed. (wheel balance)

Does it brake in a straight line or pull to one side. (brake performance)

How does the car behave at Motorway speed limits & wide open throttle acceleration?

How does the suspension sound when your going over speed bumps and rough country lanes (or UK main streets :)

Are all the panel gaps consistent  between doors, hood, fenders etc?

Look for rust around the wheel arches & sills.

Look at the paintwork under halogen lights and with dry clean body panels to check the extent of swirl marks and stone chips.

Check that the aircon blows cold.

Check that lights/windows/sunroof/hood release/seats/mirrors operate correctly.

HPI check the car, check the log book for regular servicings, check the MOT history.

Look through the history to see what was replaced/serviced recently. (brakes, clutch, radiators, ignition coils)

Ask the owner if the car has been in any accidents.

Ask the owner if the car has been tracked. (not necessarily a bad thing)

Ask the owner if the car has any existing or developing faults.

My main 996 web page

My 951 web page

Oz 951

mailto:wjgreham@hotmail.com

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