WHAT TO LOOK FOR
Spotting the rot
An S-type that looks sound can be rotten underneath, so scrutinise the two longitudinal chassis legs which meet a crossmember beneath the nose, adding essential strength. Expect problems where the chassis legs join the crossmember and the adjacent ‘crow’s feet’, which tie the front wings to the crossmember. Corrosion is common in the jacking point below the A-post, so look for distortion of the metal and poor-quality plating. This area is often bodged, as it’s complicated. Inspect the base of each front wing, looking for cracked paint; proper restoration here requires a jig for strengthening, and all rotten metal cut out. The usual giveaway is uneven door shuts, the lower front corner sticking out while the window surround is in contact with the door jamb. Other rot spots include the floorpans, wheelarches and back of the sills, along with the spare wheel well’s centre section and the two fuel tanks. The trailing edge of the boot rusts, as do door bottoms.
Offered in 3.4- or 3.8-litre forms (S-type) or 4.2-litre (420), the XK engine demands regular maintenance. Make sure the engine doesn’t sound hollow or rattly and that the oil is clean. With a cast-iron block and alloy cylinder head, antifreeze levels must be maintained to stave off internal corrosion. A healthy engine will show 40psi at 2500rpm, although senders and gauges aren’t always accurate. Lots of smoke on the overrun or when the throttle is blipped suggests worn valve guides. A light metallic tapping on tickover could be tappet buckets lifting. Specialists charge £1500 plus to fix things, but complications such as corroded water ports inflate the bill. Oil weeps are normal, but if it’s a torrent the rear crankshaft oil seal has probably failed, signalling a complete rebuild. Specialists charge £4500 plus, or you could do the work yourself for £800, but it’s an involved job that requires a special tool plus knowledge to fit the rope-type oil seal.
Until September 1965, manual S-types featured a four-speed Moss transmission without synchromesh on first. It’s a strong unit, but expect some wear on hard-driven, abused or high-mileage cars. Parts for this gearbox are scarce, so rebuilds are pricey. Later S-types and all 420s came with an all-synchro ’box that’s also tough, but much harder to find on a used basis. Whichever is fitted, make sure it doesn’t jump out of gear and check that you can select ratios easily. It’s possible to convert to a modern Borg Warner five-speed manual gearbox, but the parts alone cost £4000. Overdrive was optional for all S-type and 420 derivatives, and most cars came with it; problems are usually down to clogged filters or dodgy electrical connections. Also check for slipping of the clutch, as fitting a new one means removing the engine while a three-piece replacement kit is