I have had a MK1 TT Roadster since new (import, 2001).
The MK2 is probably a better driver's car than the MK1 (although the steering is a bit too light and vague in my opinion) but personally I prefer the MK1 for both the looks and size although the MK2 has a neater roof folding mechanism. The MK2 is larger so if you are tall its the better option.
Engine wise, I would suggest that the 225 is a better bet than the lesser 1.8 versions as the engine itself is built much stronger. The 225 version is also better equipped with Xenon headlamps, 6 speed and DIS as standard.
4 cylinder vs. 6 cylinder would be a personal preference, the V6 sound is better than the 4 pot but worse fuel consumption and extra weight of the engine are negatives when the car is a bit too front heavy already with the 1.8.
Things to look out for on the MK1 Roadster.
The body should be generally good as it is galvanised although check the sills under the doors. Although they are non-structural, the underseal is thin, particularly at the front arches and stones can chip the paint and result in it looking cosmetically untidy. If there is rust on the body then its probably there because of accident damage. Note that the front wings and bonnet are aluminum for weight saving so won't rust. If the front wings are rusted then they are a non-OEM accident damage repair.
Check suspension arms for rust too, they can get bad if the car's been driven at winter on salted roads.
The car is relatively heavy so the suspension is worked hard. I would expect wishbone and ARB bushes to have needed to have been replaced by now (unless the car has had light use) so check for noises when driving.
Check that the soft top opens and closes properly (and quietly). If it has been used a lot, the microswitches can wear causing the mechanism to not think its fully open/closed when it is. The dash roof indicator should go out when the roof is fully open / closed. The hydraulic system is sealed and cannot be topped up in servicing. It doesn't need to be unless something has failed and the fluid has leaked so if the motor's struggling then repair is necessary.
Check for dampness in the passenger side compartment under the roll bar inside the car and the boot box under the roof. The roof relies on drain channels inside the car to allow any water to run out in front of the rear wheel arches. If these are clogged by dirt then the water overflows and runs inside the car when it rains.
The 1.8 should be reliable if serviced properly. Check that the oil changes have been done to spec and that the timing belt has been changed recently, if not, do it! An unmodified engine might be a better bet at not being worked hard! Listen to the engine and make sure you don't hear any exhaust blowing from the engine bay. The exhaust manifold has been known to crack so a sound of blowing could indicate a costly repair is necessary.
The dash instrument issues are well known. The most common fault if there is one is that the gauges don't read zero correctly when the power is on so the needle is "offset" upwards. This mostly affects the fuel / temperature but sometimes the speedo and revs too. A rarer fault is that the needles jump up and down on their own! You can check if the dash is OK when inspecting a car but I wouldn't worry about it failing as reputable repairers will be able to fix any fault for a fixed price. DIS LCD pixels dying is as any Audi of that era.
The sensors used by ABS system (acceleration and yaw) had reliability issues around this time. If they are going to fail, given the age of the car, they probably have done so and been replaced so if the ABS is working properly then its probably OK. They are easy to change, but not cheap.
As with any petrol car of this age, lambda sensors will fail as they have a lifespan. Again, if the car has been maintained properly and everything is working correctly, then this should be OK but if not, expect the engine light to be on! Make sure that the engine light itself works and hasn't been "disabled" to hide a fault!
Overall, look at condition and history. Good condition and well looked after with higher miles will probably be better than a lower mileage neglected car.
regards
Andrew
