On the face of it spark plug replacement looks a little bit daunting on a 996. After all they are in a silly place, and I am more used to being able to change plugs on a 4 cylinder turbo engine in about 15 minutes from above. Access is not the best on the M96 engine, but in reality with the right tools and good preparation it is not too difficult a job to do. It is certainly easier the second time round!
I’ve written this article because during my internet research there were some areas I was unsure of and limited pictures of the ‘hard to reach’ areas, which made the thought of doing the job more daunting, so I hope this additional information helps further. I have included some pictures of the most difficult to reach plugs for reference.
Note: It goes without saying that anything you do, you do so at your own risk. Always support the vehicle properly on axle stands if you are attempting this on the ground. I strongly recommend a vehicle ramp is used, it makes the process much much easier to accomplish and is a lot safer.
First off a good tool kit is essential.
¼ inch and ⅜ inch ratchets (a ½ inch one will also come in handy), a ⅜ and ½ inch breaker bar, 3 inch and 6 inch extensions (¼ and ⅜ drive), T40 male torx ¼ drive, E10 female torx ¼ drive, 13mm deep and short sockets ⅜ drive, 17mm deep socket (⅜ drive), a good spark plug socket. I bought a Laser Tools 3587 16mm extra long spark plug socket specifically for this job (others are available), and it features a useful universal joint on the end. Overall length is 130mm and it is ideal for the M96 engine. This type of spark plug socket was something I had read about elsewhere. You will also need a 19mm wheel bolt socket and being lazy I also have a Milwaukee ½ inch battery operated impact wrench. A good pair of mechanics gloves to limit knocks and scrapes, although you’ll probably need to remove them for the fiddly work. Oh and plenty of penetrating fluid such as Wurth Rost-Off Ice. A rubber faced mallet may be useful, and probably a grinder and someone who can tack weld (although this is not essential).
If this is the first time you are attempting this job I would also advise having new stainless steel nuts, bolts and washers as replacements and some Wurth AL1100 anti seize spray or similar. The idea being that if all the original mild steel nuts and bolts are replaced with stainless parts and given a good coat of AL1100 there is a very good chance that come the second time around everything will come apart far far easier. Other anti-seize products are available, I have always found AL1100 to be very good. Take care when securing stainless nuts and bolts to prevent galling (google as required).
Suggested stainless nuts bolts washers:
14 x M8 x 25 washers (repair type)
2 x M8 x 140mm bolt
2 x M8 x 70mm bolt
10 x M8 serrated flange nut
4 x M8 spring washer
4 x M10 x 55mm (or 50mm) carriage bolt
4 x M10 nut
12 x M6 x 25mm or 40mm screw (coil pack)
6 x M8 x 25mm (or 20mm) bolt
After some research to gain better access it appears that removing the exhaust tailboxes each side is a good idea. I concur wholeheartedly; it makes access to the coil packs and spark plugs so much easier.
With the car raised safely, remove the rear wheel. Spray the exhaust sleeve bolts and the exhaust bracket bolts with plenty of Rost-Off Ice or similar – it may help. The tailboxes are held on by 3 x 13mm head head nuts on the bracket onto the engine. Access is tight but a ⅜ ratchet will do the job. Loosen them where possible, but do not fully remove. Be prepared for the existing M8 studs to snap off, the likelihood is that they will be pretty rusty on a 996. If the studs snap take car the mailbox does not drop off! There is also an exhaust sleeve between the cat and the tail box held on by two 17mm nuts and carriage bolts. They will, unless replaced recently be rusty and seized! These shifted with a breaker bar to a certain extent, but boredom set in with me and I used an impact socket and the impact wrench; it dealt with them in seconds. Once undone slide the sleeves in board as fart as they will go toward the lambda sensor. Now support the tailbox and undo the 13mm bolts the rest of the way (fingers should do the job assuming there are some studs still left attached to the bracket!) and drop the tailbox down and off the car.
If the studs have snapped, then new ones will need to be welded on the the bracket, so it will need to be removed from the tailbox.
As an aside the lower stud was already missing from the right hand bracket, obviously snapped when the Dansk tailboxes had been previously fitted.
On the left hand bracket only one stud snapped.
Undo the two M8 nuts/bolts and remove them (13mm hex head). Tap the bracket off the tailbox. Grind off the stud heads and then tap out the studs using a punch and hammer supporting the bracket on something. Then tack weld on some new M8 x 20/25mm stainless bolts. Tap the bracket back into the fittings on the tailbox and replace the two bolts, washers and nuts. At this point do not tighten them as there is some adjustment that you may need to do when you refit them to ensure the tailpipe sits square in the bumper cut-out. You will need 2 x M8x140mm and M8x70mm, 8 x M8 washers and 4 x M8 flange nuts to do both brackets. I also used a spring washer under the bolt heads onto the washers to ensure they do not come loose.
I had 6 new M8 bolts welded into the original brackets,.
If you cannot get new bolts welded to the brackets it is likely that M8 bolts with a serrated shakeproof lock washer under the head will work, as there is enough clearance to get a spanner up between the tailbox and bracket to allow them to be tightened when they are fitted back onto the car.
Here are some of the take-off parts.
View with the tailbox removed. Now is a good time to treat the face of the bracket with some rust converter such as Dintirol RC900.
Remove the heat shield, 2 x torx screws using an E10 socket on a ¼ drive ratchet.
Now to remove the coil packs and plugs.
At this point it is worth noting in which order the cylinders are numbered for reference. If you already know, indulge me! From the timing chain end/multi v drive belt at the rear of the car bank 1 is to the left and from rear to from cylinders 1, 2 and 3. The right hand side is bank 2 and cylinders 4, 5 and 6 from rear to front.
I decided to use NGK Laser Platinum spark plugs, based on my experience of them from the performance market and from using them in previous cars. It also goes without saying that as far as spark plugs are concerned NGK are certainly a reputable brand.
I started with the right had side because there is one very accessible coil pack and plug namely number 6 (frontmost) but also the hardest one to gain access to is at the rear, number 4.
I remove each coil pack and spark plug one at a time, rather than remove all the coil packs first. Start with an easy one! Unclip the plug on the coil pack. Under the rubber boot is a small retaining clip (be gentle). Press this through the boot, about 10-15mm above the coil pack and you will hear a ‘click’, carefully then slide the plug and boot upwards until it comes clear of the coil pack. You will see the retaining lug on the coil pack and if you slide the rubber boot up slightly you will see the retaining clip. Take care not to break these clips! I would advise doing the accessible one first to practice and become familiar with how the plugs on the coil packs work. Also when removing the plug make sure the orange rubber seal does not fall out, or get twisted when the plug is re-connected.
Now undo the two retaining screws, T40 male torx. Then carefully pull the coil pack (gently but firmly) from the plug hole and slide it out. Then remove the spark plug using your plug socket and withdraw the plug. With the new plug firmly held in the socket, hand tighten carefully until it starts to tighten down onto the gasket, then tighten as indicated on the plug box, ½ to ⅔ of a turn usually. From experience I always tighten spark plugs by feel, the suggested Porsche torque setting is 30Nm, but remember DO NOT over tighten the plug into the cylinder head. I used a little AL1100 on the plug; I know Porsche service literature advises not to, but I always have on spark plugs will no issues. The plugs I removed which had previously been fitted by a specialist did also have some anti seize on them. Make of that what you will with regards to who is right and who is wrong.
I always wipe down the coil packs when they are out and check them for signs of cracking or damage to the rubbers.
Refit the coil pack, pressing it back into the plug hole then re-secure with the screws. I used some new stainless M6 x 40mm torx head screws with a smear of AL1100 to prevent them seizing. Stainless heads will also stay looking newer for longer. Note the screw length; some use 25mm screws, others use 40mm screws. Refit the 3 pin plug onto the coil pack.
Repeat for number 5 and number 4. You will find as you withdraw the coil pack on number 5 you may need to rotate it through 90 degrees to allow the plug to clear the chassis; the same applies when refitting.
Cylinder 4. It is tight but not impossible to access, although you are restricted by the exhaust bracket on the engine. You will find that to remove the coil pack you will need to rotate it towards the front of the car as you remove it and also bend it downwards slightly to remove it successfully. Here are some pictures of access to number 4 showing that the spark plug socket, 3″ extension and ⅜ drive ratchet will all fit……. just. it is easier to insert the plug socket first then attach the extension followed by the ratchet. Once undone remove the ratchet and extension and withdraw the socket with plug inside. Refitting is the reverse.
Once you have done this bank, refit the tailbox, use 3 new M8 stainless steel washers and serrated flange nuts on the bracket studs and tighten. Use AL1100 on the studs. Replace the bolts in sleeve between the tailbox to cat; use 2 x stainless M10 carriage bolts and nuts. Again on these nuts/bolts I used a liberal coat of AL1100 to help prevent seizing and corrosion so future removal should be easy.
Before tightening everything adjust the tailbox on the bracket and when the tail trim is correctly positioned in the bumper cut out, tighten the two bolts that secure the tailbox to the bracket. Then finally tighten the M10 nuts on the exhaust sleeve, ensuring it is central. There will be witness marks on the exhaust pipework to act as a guide.
Finally refit the coil pack heatshield using the two small torx screws, use AL1100 on the screws. Replace the heatshield if it has deteriorated. They are only about £15 each + VAT from Design 911
The left bank is very much the same as the right bank, 1 and 3 are pretty easy. The hardest plug and coil pack to gain access to on this bank is number 2, in the middle, access restricted by the exhaust mounting bracket secured to the engine. Here are some pictures showing access.
The bosh plugs that came out looked in pretty good condition:
I also took the opportunity to give the stainless tailboxes a clean down, removing tar sports and tarnish and giving them a polish with Britemax Metal Twins.
As removed from the car:
And prior to refitting:
Final couple of images, all back together.
Finally refit the road wheels and correctly torque the wheel bolts; 130Nm applying AL1100 as indicated in the owner’s manual.