The old transit vans especially the Mk1 are almost achieving cult status and now fetching higher prices than they were a few years back.When buying any motorhome the interior is important and should be checked for damp as one would a caravan,the rest of this guide applies to all the transit variants.
The original Mk1 had a V4 engine known as the Essex virtually the same as fitted to the corsair and Zephyr 4 .Spares for these are hard to source and the engines had problems with the timing gear,oil pump drive and over heating.They were never quiet or economical even new,but avoid one thats excessively noisy or puffs out smoke.Some Mk1 amulances were fitted with the 3 litre V6 engines which are fast but thirsty,at the other end of the performance range some Mk1s had diesel engines,they are identified along with the V6 version by having a 'bull nose' front.
The Mk2 used the pinto engine (cortinas etc) and is a better bet than the V4 although early versions had problems with a poor oil supply to the valve gear.The front part of the exhaust on the Mk1 is obsolete which means adapting other parts to fit,clutches,filters and most servicing parts are still available.Some Mk 2 ambulances also used the v6 essex ,fuel consumption is pretty horrendous but it gives the vehicle both a superb exhaust note and a respectfull performance.Some MK2s are also fitted with diesel engines,as with any diesel cold starting is a good indication of an engines condition.Be wary of arriving to see any diesel engined vehicle were the engine is already hot,a sound engine will start readily from cold and should not smoke excessively or fume through the breather or filler cap.All older diesels rattle,better borrow a friend who knows about these things to take along with you if you're unsure what to look for than take a chance on buying a vehicle that won't start when its cold.
Rust is a big problem,the early vehicles are over thirty years old and many will have had commercial use.The front crossmember is the same on both versions (the wings and front panels are different) and rots badly as do the spring hangers.These need repairing properly to keep the vehicle safe,the outer wings (especially the Mk1) rot and are now obsolete although fibreglass panels can be obtained.The door steps and sills are another rust prone area,parts are very hard to source.Doors rust but can normally be plated,a well neglected example may have rot around the rain gutters on the roof which is a fiddly job to put right.The floors and chassis sections can also become weak.
Springs settle and the vehicle should sit level.The early vans brakes were poor compared to modern vehicles and the very early brake cylinders are hard to find.Expect around mid 20s fuel consumption even driven slowly and become good at sourcing parts at auto jumbles,ebay and car boot sales,if you can do that and aren't afraid of getting dirty and welding,these vans can be fun,something the modern versions seem not to be.