Porsche Macan Turbo spark plugs and bore scoring
When I bought my 2015 Macan Turbo, it had 87,000km. It’s now hit 122,000km, and since I’m doing oil changes every 7500km it was time for another.
This time I decided not to use Liqui Moly engine flush. It’s advised to flush the engine with clean oil after using it, to ensure you remove all of the detergents, so they don’t continue breaking down the new oil.
I didn’t want to do this, and since it’s been running well, I just did an oil change, as well as using some Liqui-Moly additives which you can read more about here.
I’m getting pretty good at this now, and had the job done in about an hour and a half.
I also installed new air filters, as I didn’t know how old they were. This took only a few minutes.
I checked the service book and it recommends changing the spark plugs every 45,000km. They were last done at 82,000km, so it was time to do them too.
I’ve not changed spark plugs before, but thought I’d give it a go. I ordered a spark plug socket kit from Amazon for $30, and a set of six Bosch Double Platinum spark plugs from run auto for $125.
I find Pelican parts do great guides for jobs like this.
Here are torques for my 2015 Turbo, likely will be the same for all V6s:
spark plug, new - 25 Nm (tolerance +1.5 Nm), don’t use lubricant
spark plug, re-used - 31.5 Nm (tolerance +1.5 Nm), don’t use lubricant
fastening screw for ignition coil - 10Nm
fastening screw for coolant reservoir - 5 Nm
Plug electrode gap - 0.8mm +/-0.05mm
I got started the following weekend. The job went well, and took me about 3 hours. I was very careful removing and reinstalling the plugs to avoid damaging the aluminium threads.
The front four plugs are very easy to do. The rear two are harder as they’re obstructed. A universal joint and some extensions helps a lot.
A trick I read about on a forum is to put some tape around the extension bar to show where the ‘fully in’ position is.
This is helpful because the plug sometimes gets stuck when inserting, and it’s hard to know whether it’s bottomed out, or you just need to back out a few turns and try again to get past the rough spot.
If the plug gets jammed and you torque it down, it could strip the thread, which could be catastrophic. The blue tape gave me confidence, but I would always back out and rethread anytime it stopped, even when bottoming out, just to be sure.
I inspected each spark plug but didn’t see any signs of damage. The worst was this one that seemed to have some crud bridging the terminals. It came off with a brush of my finger.
While I had each plug out, I took the opportunity to boroscope the cylinders.
I have heard some horror stories of engines being destroyed due to bore scoring, where the piston scrapes away the protective lining in the cylinder. This leads to noise, excessive oil use, and eventually complete engine failure.
From what I’ve read, this is usually caused by poor maintenance. Long oil change intervals are the main culprit, which is why I always change my oil every 7500km instead of the Porsche recommended 15,000.
There’s been some instances of manufacturing fault, but I think it’s rare.
If I were buying a used Macan again today, I’d take the time to check for signs of this damage, at least in the front four cylinders which are easy to access.
I bought my boroscope off Amazon for $100. It’s a handy tool for all sorts of uses. Be sure you get one with at least two cameras so you can look ‘forward’ as well as ‘sideways’. Mine has 3 cameras, so it can look left and right. Very helpful.
Thankfully, I didn’t see any evidence of bore scoring in my engine. There’s the typical cross hatching which is normal.
I did see quite a lot of carbon deposits, but my mechanic said it’s below average for an engine like mine. It’d be nice to get that cleaned off one day.
After I put everything back together, I was pleasantly surprised to find the car running smoother. That seems obvious but it’s quite noticeable, the engine revs more smoothly.
In addition, the hesitation that was present at 2100rpm since I bought the car is now fixed! Another win.
New spark plugs have been the biggest improvement since the initial engine flush I did.
I’m proud to have done another maintenance job on the Porsche. It feels great to tick the box in the service book myself.
The car is due for drivetrain oil change next, so I’ll write more about that once I’ve done it.
