2.5 diesel – old but good
I HAVE done quite a few 200Tdi and 300Tdi conversions over the years. There are two types of vehicle which have provided the bulk of this work. The first is Ninetys and One Tens built between 1986 and 1990 with the 19J turbodiesel engine. This motor has acquired a terrible reputation over the years. It was the last in a line of all-iron diesel pushrod ‘fours’ which went back to the 2052cc motor first seen in the Series I in 1957. By late1950s standards it was an astonishing technical achievement, revving to 4200 rpm at a time when most small diesels struggled to get past 2500. But diesel design moved on a lot in the following 30 years, and strapping a Garrett turbocharger onto this ancient motor was a development too far. Worked hard, the engines fell to bits: cracked pistons were common even though they were supposedly strengthened, and internal block cracking also manifested itself. The 19J was a warranty nightmare.
Treated sensibly and maintained properly, it’s actually not a bad engine. A healthy 19J will pull strongly enough to keep up with the traffic, and the power delivery is more gentle than on modern turbodiesels. But most of the ones that come to me are life-expired, difficult to start from cold, blowing oil from the breather into the air filter (diverting the breather pipe into a Coke bottle is a common modification) and making all kinds of strange noises. I usually strip them of reusable ancillaries (turbo, injection pump, starter motor, etc) and scrap the rest. In a few years time I’ll probably regret that, just as I now regret all the three-bearing 2.25 petrol engines I weighed in when they were two a penny and no one wanted them.
The other main source of conversion work is ex-military vehicles fitted with the naturally-aspirated 2.5 diesel engine, for which the description ‘strong but slow’ comes to mind. These come in two versions: the standard 12J engine, and the much rarer 11J, a military-only variant which used a 19J bottom end complete with uprated pistons. Almost invariably the engines that come out of military Ninetys and One Tens are in good order, many having done very few miles since being reconditioned. The demand for these engines is not huge and I can’t bring myself to scrap them, so my workshop is gradually filling up with the things.
About the only market I have found for them is fitting them to Series vehicles in place of the earlier and weaker two and a quarter. The 2.5 gives a significant improvement in performance compared to the 2.25. Drivability is better: the earlier engine has a fullygoverned injection pump whose all-ornothing throttle response takes some getting used to. The 2.5 has a proper vacuum pump to power the brake
servo, replacing the utterly hopeless Heath Robinson-inspired arrangement of flap valves, cranks and tanks which somehow found its way into the Series III. And the 2.5 has a belt-driven camshaft and injection pump. These days we are encouraged to think that chains are better than belts as they never need changing. However, the camchain on the 2.25 diesel stretches like knicker elastic, the injection pump is driven off a skew gear with plenty of slop in it, and so the pump timing wanders around and makes the annual MOT smoke emissions test something to be dreaded. The 2.5 does not suffer any of these problems. The timing belt is very strong, has a 60,000 mile change interval, and if it does break you’ll usually get away with just a few bent pushrods.
The 2.5 diesel bolts straight onto the Series gearbox using the Series clutch. The Series manifolds bolt onto the 2.5 head. The radiator and heater hoses need a bit of fiddling around, and the cooling fan has to come off as it is a little close to the radiator. Use the Series fan with the holes drilled out to 8 mm, M8 Allen bolts, and the earlier (fixed fan) 12J water pump. The only real obstacle to dropping a 12J into a Series vehicle is that the injection pump fouls the offside engine mount on the chassis. I get asked quite often how to solve this problem: the following advice also applies if you are dropping a 19J engine into a Series, or a Defender 200Tdi engine (type 11L) for those lucky enough to be able to find a good one.
On the nearside, use the standard Series engine mounting bracket. You will find there are two pairs of bolt holes in the block. For fitting the engine into a Series, bolt the bracket to the front pair. On the offside you need to cut the complete mounting bracket off the chassis, along with the battery tray, which gets in the way of the timing case. You can either relocate the battery elsewhere (under the passenger seat, for example) or fabricate a removable tray which can be bolted in after the engine has been fitted. The new engine should come with a long mounting bracket which curves under the injection pump: keep this. Now all you need is a bracket to weld to the chassis, and you already have one: the mounting bracket bolted to the offside of your old engine. Turned upside-down and welded to the chassis, this allows the engine mounting rubber to sit at exactly the right angle and distance from the chassis rail. All you need to do is weld it in the correct place.
That is easier said than done. What you need to do is get the new engine on a crane, slide it into the engine pay and bolt it up to the gearbox (leave the clutch off for now to make fitting easier), then carefully lower the engine until the nearside is resting on its rubber mount and the engine is sitting all square and level in the engine bay. The starting handle hole in the front pump should line up with the front crank pulley bolt: if you have this bit right, your engine positioning can’t be far off. Now offer up the offside chassis mount, and when you are happy that it is correctly positioned, clamp it in place and tack weld it. Remove the engine and weld all round: you might just be able to weld it with the engine in place but I wouldn’t advise it. Apart from anything else the heat won’t do the rubber mount a lot of good.
I recently had a Series III in the workshop to fit a nice ex-military 12J engine which had just come out of a One Ten. (And when I say “just come out”, it was still warm when I started fitting it to the Series.) Being even more short of space than usual I didn’t want the new engine to be sitting on the workshop floor for too long, so I came up with the kind of cunning plan that results from having far too many engine bits lying around. At the back of my workshop was a bare 12J engine block and in the parts store I had a small stack of flywheel housings. I bolted one to the other. Result: one dummy engine, much easier to get in and out of the engine bay than a fully dressed one.
It has now been returned to the engine dump at the back of the workshop, where it will sit until either I am asked to fit another 12J into a Series, or I run out of usable engine blocks for rebuilding. That might take a while.