If you plan to keep it relatively standard, I'd avoid the quattro and go for a LCR (but then I am biased...)
Same power at the engine, less weight and losses getting it to the wheels. Unless you're planning on going above 300bhp or so then there's no real need for the Haldex system, and if you
are planning on going above that then you're going to need to drop in rods etc anyway. With the Leon you also get 323mm Brembo 4pots (very similar caliper to the GT Junior), rather than the standard VAG front sliders over a 312mm disc. Of course you can bolt these on to an S3 regardless should you chose to go down that route, it'll just cost you a few hundred quid to get involved, no biggy.
The 1.8t is a great lump, easy to work on at home and incredibly tunable for minimal outlay. The A4 FWD chassis (not Audi A4, that's the chassis designation. Used in mk4 Golf, Leon, A3, TT, Octavia, Beetle) isn't the best, but with a bit of love can be significantly improved. From the factory relatively understeery and a bit numb, so if you do get one add a rARB to your list early on. The S3, LCR and TT benefitted from upgraded suspension components to match. Hubs were better geometry for a lowered car (~25mm lower than the standard Leon/A3/Golf from factory anyway), the wishbones were cast rather than 2-piece and had camber adjustment (earliest TTs had 30mm rather than 45mm bushes too which helped, though Audi numbed this down as they were too responsive for most users), ARB mounted from long droplinks on the strut rather than the wishbones, the latter causing rubbing issues when lowered. Steering rack is "quicker" at ~2.7 turns lock to lock vs ~3.4 for the standard models. Plus, of course, they were fitted with a k04 blower (k04-020, -022 and -023, all nigh-on identical) rather than the k03/k03s units on the 150/180bhp models lower in the range. Ignore the k04-001 that is occasionally mentioned, it's just a k03 for all intents and purposes but some folk will claim it's a significant upgrade. It's not.
With regards to buyers' guide/points to note, I guess key points would be along the lines of:
- Coil packs can be a tad iffy. Some folk seem to replace them every couple of years, others of us (myself included on 2x 1.8t cars) never have an issue
- There's a snakes' wedding of vac hoses under the bonnet, which with age can become brittle and result in boost leaks, and therefore running issues. Very easy to put right, and in actuality, a lot of it can be removed and simplified for minimal outlay. Can be helpful in negotiating a lower price knowing it's an easy fix if you find the right seller.
- Similarly, now that these are cheap they're getting into the hands of the great unwashed and many are being poorly modified. These engines rely on a MAF system so when folk stick VTA dump valves on it throws fuelling out and will run a touch lumpy. Don't be sucked in by shiny DVs, the stock 710p diverter valve is dirty cheap and the best of the bunch really.
- Door seals are s**t on the Leon, though can be sorted out in a couple of hours with a roll of butyl tape.
- Water pumps occasionally (not overly common) have issues. Factory impeller was plastic and with age has been known to fail. Can replace with a new version (changed to better spec plastic) or a metal impeller version (some leak from the shaft) but really it's very infrequent.
- Oil pickup in the sump can get clogged. New strainer is 2 bolts and about £12 IIRC, though you can just drop the sump next oil change and clear it out. Run a decent synthetic 5-30w and you'll be fine.
Other than that it's just usual car buying stuff :up:
Worth noting that the above aren't particularly frequent, so don't mistake me listing that lot as the cars being s**t. Think of it more as a comprehensive list of what's been known to go wrong with a tiny subset of cars on one of the widest selling chassis of all time in ~20 years of existence. In around 6 years of ownership of 1.8t cars I've only ever had door seals fail and a couple of vac leaks (with the exception of self inflicted failures from playing around with things), and I'd have another tomorrow without batting an eyelid.
Any specific questions etc, I'm happy to try and answer for you either here or via PM :blush:
