There's really very little unique in terms of problem areas with the +2 that isn't covered by the Elan.
Engine - the twin cam will burn oil as the valve guides wear. Typical oil leaks around the front timing cover. Weber or Strombergs? Stromberg parts are getting harder to find.
Gearbox - clutch hydraulics are the weak link
Diff & drivetrain - rubber donuts, look for age, cracking
Brakes - rear pads are getting more difficult to find. Check hydraulics, master and calipers for leaks
Electrics - a sore point, LUCAS!!!! Check switches and general wear on the loom. Corrosion usually means resistance which can lead to heat and then fire danger.
Cooling - cooling problems in these cars typically point to 2 areas: Radiator (undersized) and the waterpump. If the waterpump is leaking assume the engine needs to be rebuilt. replacing the pump requires head and pan removal (to remove the pan you pretty much have to pull the engine)
Body - Spider cracks are the biggest issue. They're tough to repair. Check the headlight lifts. They are activated by vacuum pods that rust out. Also the crashpad is prone to cracking and OEM replacements are un-obtainium. Cracked wood dash can be repaired or replaced easily (throw money at it).
Chassis - Look for rust!!!! Rust around the base of the shock towers (F & R) is especially bad. I've seen the towers fail and literally break off with bad results.
Suspension - Look for rust, bad bushings and damage. The A-arms are stamped mild steel and are prone to damage and rust. Front uprights are Stanparts (Triumph) as is the steering. Springs & shocks are still available.
That's a quick & dirty overview... for more info check out:
LotusElan.net: Your Complete Lotus Elan Information Source.
Index page
and the "tech" section of the Golden Gate Lotus Club site
GOLDEN GATE LOTUS CLUB - Lotus Car Club, especially this article that appeared in "Classic Motorsports" magazine -
Elan Buyer's Guide
Cheers,
Kiyoshi
P.S. post a few pics!!!