Thanks to Barr_End for this excellent list of maintenance topics.

The standard Audi maintenance schedule does not cover many of these issues, and from over a decade of Mk2 experience, these recommendations should be followed, especially by new owners who may not have a service history for their TT.

"Personally I'd do and have done a lot more than post people on this forum would even know about, purely from following TFSI tuning page on Facebook ever since I've owned my TTS. The TFSI engine variant is in a lot of VAG cars, not even the engine code of a CDL is unique to just the TTS.

My best advice would be to take a long search within that page for information and posts of what happened if you do not".

- Barr_End

I. ENGINE -

Decent oil - This is number 1 thing to get right in my opinion. Again in this Forum you'll be told you're mad for going out of the VW 501/5@4 emissions spec crap. However there is a reason why too many owners to count and the leading TFSI tuner recommend 5W40 millers nano drive NT+. Also included in the link below is the DIY for oil and service interval reset -
Cam Follower for the High Pressure Fuel Pump - It's a £30 part and 15-20 minutes to change if you're handy on the spanners. For peace of mind you're nowhere near a £2k garage bill to fix it when it goes wrong. If you see silver through the hardened black coating, replace it!
Sump clean out and fresh oil pick up - This speaks for itself but worth doing for peace of mind so you won't have the dreaded red oil pressure light.
Cam Belt - Standard service item

Cam Chain - It makes a real difference in engine noise and feel of the engine, chains are not a lifetime item, they stretch and their tensioners become brittle. Early tensioners (Rev H) had a major recall (at least in the US) and there's a TSB on the subject. If you have a VCDS, you can verify chain stretch -
Dipstick - Sounds mad but the older orange dipsticks have been revised as they go brittle and snap, putting little lumps of plastic into your oil/sump. Also, the o-ring near the handle can fail leading to a vacuum leak -
Injectors - TFSI injectors only have poor little paper element filters which can easily break down, especially on cars where loads of fuel additives have been used. Injectors can be flow tested, filters removed, cleaned, metal mesh filter baskets inserted then flow tested again to make sure they are correct. Another item that's well documented in TFSI world and it well worth peace of mind - (Fuel Injector Cleaning Tester Parts | Fuel Injector Clinic | England) -
Intakes - Whilst you're there, worth while having the inlet & back of the intake valves walnut blasted. TFSI build up carbon due to being direct injection and not having fuel to clean off the back of the valves. No amount of fuel additives or fuel cleaners will help due to the design of direct injection -
Plugs - Decent plugs for the price are a must! Don't put any lubricant on the threads. Adding copper paste is an old-school solution and is not only unnecessary (new plugs have a plating designed to provide lubrication) but will cause a false reading on your torque wrench leading to possible over tightening. Be cautions of discount part websites and resellers like Amazon or eBay as fake spark plugs are becoming quite common. When in doubt, just buy them from VW or Audi.
Diverter Valve - Known weak point on the boost side of things, get a fresh Rev D after checking if yours is split. Very easy to remove on the CDL with it being at the front of the engine bay -
Thermostat - Known TFSI issue, easy to identify. Car will not hold 90° on the gauge will be up at higher speeds and only sit at 90° when in traffic or slow moving. Affects the ECU feeling a lot. Bastard of a job but needs must!
PCV - Another known weak point for failure - not massively expensive - I haven't seen any symptoms in mine so still running stock one for now -
Coil Packs - Most will say "replace for red R8". There's next to no difference in the stock TTS/RS could internally to the "uprated" R8 coils. The stock TFSI coils on the other hand there is a difference. I'm still on my stock coils 115k+.
Accessory Belt, Tensioner & Idler Pulley - A good video from Gates on why these should all be replaced together as a matched set. Also a DIY for the VR6 3.2 (BUB) engine -
Primary Air Filter - With links for the 2.0 TFSI and 3.2 VR6 engines -
Secondary Air Pump Air Filter - One of the more obscure filters for VR6 3.2 (BUB) engine -


II. FLUIDS -

Gearbox - Obviously fresh fluid is a no brainer regardless of DSG or manual as it's always going to help more than cause issues -
Haldex & Final Drive (Diff) - Regardless of what a service shop tells you, the Gen2 and Gen4 Haldex have two filters and they should be changed with the oil. While they're back there, have the final drive fluid changed too. Fluids and filters are cheap insurance -
Coolant - Audi states it's lifetime, but there's no such thing as lifetime anything except taxes. If your vehicle is over 10-years old or touching 100,000-miles it's a good idea to have it flushed and replaced. While they're in there, be sure to ask them to give the radiator, temperature sensor and the oil cooler a good look-see since they're known to fail due to corrosion.
Fuel Filter - Tucked up and hidden away near the fuel tank is the (petrol) fuel filter which should not be over looked especially since it's not on the Maintenance Schedule. Diesels also have a fuel filter so be sure to change that one too.


III. SEALS & DRAINS -

Coupe - Good link here for sorting all the various body seals and drains -
Roadster - In addition to the Coupe's drains, there are two drip drays located below the roof flaps. These and the drain hose are unique to the Roadster so be sure they're clear. A blocked drain or disconnected hose can lead to water ingress into the bulkhead, which can not only dampen your carpet, but lead to corrosion of the wiring on the fuel pump -
Plenum Removal for Drain Inspection & Cleaning -There are two drains under the plenum (the plastic cover under the wiper arms) which can get blocked when debris gets under the plenum cover. This can result in water coming into the cabin through the HVAC intake vent.


IV. BITS & BOBS TO DO EVERY YEAR -

Spoiler - The two spoiler hinges should lubricated, especially in city cars that never get up to deploy speed and those who fail to raise and dry them after a car wash. Simple to do, but shouldn't be over looked -
Level Sensors - The level sensors have a ball and socket arrangement which should be cleaned and lubricated periodically. If they seize or break, they can trigger a headlight or a Mag Ride fault.
Seals - Door and trunk seals should be give a nice coating of silicone lubricant one a year to keep them pliable and prevent ice from sticking to them and the metal work resulting in them becoming torn or damaged. Here in Europe, NIGRIN Gummi-Pflegestift works great, especially in winter to prevent stuck doors and trunk lids.
Wipers - Replace them before the rainy season whether they need it or not. You won't realize how much UV has degraded the rubber until you need them after a long, hot summer.
Washer Fluid - You don't want summer washer fluid freezing up and cracking your headlight aliens come winter. Be sure to start putting the blue -20° washer fluid into the bottle towards the end of summer and be sure to flush the aliens so the lines are full of blue fluid. If washer pumps or level sensors leak or fail, this post will help you get them sorted -
Washer Jet Cleaning and Adjustment - To make sure your jets are clean and the spray pattern is correct, take a look at this post.

Key Fob Battery - The smallest things can cause the biggest headaches. Simple #2032 coin battery replacement. Make battery replacement part of your New Year's celebration -
Cabin Air Filter - Get the MANN charcoal impregnated version as it does a better job of keeping fumes out. Very easy DIY -


V. TAIL LIGHT FIX -

While not technically a maintenance or service issue, the Mk2 TTs have a well known earth/ground fault that causes the tail light bulb out warning to come on the DIS even though the bulbs are perfectly okay. This link will show you how to add a non-OEM earth/ground wire to both tail lights which will solve the problem -
https://www.ttforum.co.uk/forum/viewtop ... 6#p8866786


VI. ROADSTER CONVERTIBLE TOP -

The Roadster top needs special care just like any soft top. Keep it out of the sun as much as possible (use a half cover if possible) and never stow the top if it's damp or wet. Here's some basic care tips from the convertible top manufacturer -
There are two drip trays located directly under the roof flaps. Use a length of flexible tubing, duct taped to a vacuum cleaner hose, to get any debris that may have ended up down inside this area. This will help prevent the drain tubes from becoming blocked, leading to water ingress in the bulkhead and behind the seats. Just open the top about half way, and the roof flaps will be up for ease of access.
To avoid problems with the operation of the convertible top, the DYI linked below requires removing the Roof Flap Servos and cleaning out the grease that migrates onto the electrical contact surfaces. If you can handle a T20 torx and a 10mm socket wrench, then it's easy enough to do this little project yourself.


VII. WORKSHOP INSTRUCTION MANUALS -

Just about all the major topics listed above can be found in the workshop manuals which you can download here -


VIII. YOUTUBE VIDEOS

There are a ton of YouTube videos that cover all sorts of maintenance and repair topics. Two of my favorite sites from the USA are Deutsche Auto Parts and the Humble Mechanic. While they are primarily VW guys, the engines and components are nearly identical and they also get into VCDS and OBDeleven programming.

Deutsche Auto Parts
HumbleMechanic

For anyone with a 2.0FSI engine, this Italian video is pretty good -

FSI 2.0 Turbo Engine Maintenance - Informative Video
https://www.ttforum.co.uk/forum/viewtop ... &t=1962311

IX. OBDII DIAGNOSTIC TOOLS

To avoid guessing when things go wrong, an OBDII diagnostic tool is money well spent. The two most popular are the Ross Tech VCDS and the OBDeleven. Both have their pros and cons, but you'll have to decide which is the best suited for your needs.

X. AUDI SCHEDULED MAINTENANCE INTERVALS

Although Audi omits a number of significant maintenance points this is the "go to" list for recommended mileage for proper service. Keep in mind some parts, especially those made of rubber or elastomers, will degrade over time regardless of mileage. So keep your vehicles age in mind when thinking about replacing accessory belts and suspension fittings. Generally speaking, all the published Scheduled Maintenance Intervals are the same for all Mk2 TTs.

This is the information from the North American version -
"At 110K miles (175,000 km) replace timing belt (2.0 TFSI engine only). Check condition of timing belt tensioning system, dampening pulleys, and idler pulleys and replace if necessary (2.0 TFSI engine only)."

This is the information from the Audi UK website -
"The cambelt (timing belt) is one of the hardest-working, most crucial parts of your engine, so it’s important to have it replaced by Audi experts. It’s a procedure that we recommend is carried out every 5 years due to the potential damage to your engine in the event of breakage.

As you can see, even Audi isn't consistent in their own published information. And you may get a different mileage recommendation from Forum members. Be aware that the Service Interval publication is a bit questionable as Audi has omitted some key components such as the High Pressure Fuel Pump Cam Follower, intentionally deleted the Haldex Filter after 2006. Audi also considers coolant "lifetime" which is nonsense. This list below is probably and most complete you'll find and should be followed.