Norfolk Garage
From a Series IIA that’s cutting out to an overheating problem on a Ninety and an oily Defender 200Tdi
One of the occupational hazards in dealing with quirky old vehicles is that occasionally you get so immersed in arcane technical issues that you overlook the blindingly obvious. Sometimes you need to take a step back, get yourself a nice big mug of tea and a chocolate biscuit, and wait for the solution to come to you. This was how I ended up solving an overheating problem on a 1989 Ninety that came into the workshop just before Christmas. The vehicle had originally been powered, if that isn’t too strong a word, by a 19J turbodiesel of the type that kept Land Rover’s warranty department busy throughout the second half of the 1980s. This had blown up (as tends to happen with ageing 19Js) and had been replaced by a 200Tdi engine salvaged from a scrap Discovery. This is an excellent choice in my opinion: I must have done around 50 of these conversions myself, and they are worth the money for the improved fuel economy alone.
The Discovery version of the 200Tdi (type 12L) differs in a number of respects from the Defender variant (type 11L). The latter is pretty much a drop-in swap for a 19J, bolts straight up to the gearbox bellhousing and can even use the same exhaust system from the downpipe back. The 19J exhaust is considered by some to be a little restrictive compared to the correct 200Tdi system, but I suspect there isn’t actually a lot in it. The Discovery engine is a rather trickier installation prospect, with a low-mounted turbo, high-mounted injection pump and a completely different front end. The bellhousing bolt pattern on a Discovery 200Tdi differs significantly from that on a Defender, and has two locating dowels on the back face of the flywheel housing, which the Defender lacks.
It is not difficult to modify a Discovery flywheel housing to bolt up to the LT77 gearbox used in the Ninety and One Ten, since the 11L and 12L engines share the same casting for the flywheel housing. The Discovery variant requires the dowels removing (they are a tight fit and sometimes need drilling out), four existing holes drilling and tapping to take M10 threaded studs or bolts, and four other existing holes counter-boring to takeM10x 80 Allen bolts. These long bolts clamp the flywheel housing to the cast strengthener between the engine block and the sump. On the Discovery this role is performed by long hex-headed bolts through the bellhousing. None of this is especially difficult, and if you do not possess the correct counter bore (around £30) you can use countersunk-headed bolts, which will be plenty good enough. However, there are still people out there who will claim that the 12L engine bolts straight in – and the Ninety now in my workshop was an excellent example of what happens if you take this approach literally.
The immediate problem to be solved was that the starter motor was engaging with the flywheel ring gear on about one attempt in every 20. The starter looked fairly new, so the owner thought the problem was likely to be caused by a worn ring gear. As the flywheel housing was missing all the studs across the bottom (being an unmodified Discovery housing) I was tasked with removing the engine, replacing the ring gear, modifying the flywheel housing, tidying up a few other areas of the conversion (wiring and pipework) and putting the whole lot back together. The owner mentioned almost in passing that the temperature gauge appeared to be reading high and might need replacing.
I set about removing the engine, uncovering various bits of bodgery along the way (four different sizes of screw to hold down the transmission tunnel, and not a single washer between the lot of them) and soon had it sitting on the floor. The flywheel ring gear didn’t look any more worn than they normally are, so I turned my attention to the starter and found that when I applied power to the solenoid, the drive gear was only moving about three-quarters of the way up the shaft. I dismantled it but could see no obvious cause, so I gave up with it and dug a good secondhand starter motor out of the stores. I then turned my attention to the flywheel housing.
When I had separated the engine and gearbox a chunk of aluminium with a stud attached to it had fallen onto the floor. The reason was not hard to find. The flywheel housing still had the Discoverytype locating dowels in it, which protruded about 2 mm from the mating surface. When the engine was slid onto the gearbox the dowels had prevented the two from snuggling up together as they should, and whoever had fitted the engine had carried on tightening the nuts until the aluminium casting around one of the studs fractured under the strain.
As a by-product of this bodgery, the engine and gearbox had not been running absolutely square to each other. The spigot bush in the centre of the flywheel had been badly chewed by the end of the gearbox mainshaft running out of true, which probably explained why the owner had complained of clutch judder when moving off from rest. The clutch cover (an unbranded copy of a Valeo heavy-duty clutch, and only a couple of years old) had a bent diaphragm finger which was not something I had seen before. Whether this was connected to the engine to gearbox mating issues or just a manufacturing defect I cannot say.
“I have never really seen the point of radiator muffs, at least in East Anglia”
I machined up the flywheel housing to accept the necessary bolts and studs, drilled out the two offending dowels, and turned my attention to the broken bit. Fortunately there was enough intact threaded hole left to take a slightly longer stud, so I drilled out the threads in the broken portion and glued it back onto the housing with metal-reinforced epoxy, with a nut and washer on the stud to hold the chunk of metal in place until the glue had set. The engine went back together with a new crank seal ERR2532 and backplate gasket ERR1440 (a nice Elring one with preformed beads of sealant; not one of the cheap paper versions), an AP Driveline clutch replaced the defective one, and before long I had the whole thing back together and ready for road test.
The test showed up a couple of issues. Firstly there was a slight exhaust blow from somewhere. I soon traced this to the manifold gasket which had failed across number one exhaust port. The gasket on a Discovery 200Tdi engine can usually be changed without having to undo the turbocharger oil pipes but it is a fiddle, especially when removing the bolts that hold the manifold support bracket to the block. The second problem was that after about five miles the temperature needle started climbing past the halfway mark until it was hovering just short of the red zone. Back at base I felt the radiator hoses and found that the bottom hose was almost the same temperature as the top hose. Clearly the cooling system was struggling to cope.
At this point I confess to getting sidetracked because there was a third issue arising from the road test, which was that the vehicle did not feel nearly as frisky as a 200Tdi-engined Ninety should. It lacked the usual bark and seemed to be a bit down on power, so I went down the route of trying to establish why.
I checked the injection pump timing and found it to be a couple of degrees retarded, but even with this corrected the vehicle was little better although it sounded much crisper. I played around with fuel pump settings a bit, checked stuff like the turbo wastegate and the boost fuelling diaphragm on the injection pump, and even went to the trouble of using a dial test gauge to make sure that the camshaft timing was correct. I have had two vehicles in recently for cambelt changes where the camshaft pulley was one tooth out of alignment and had presumably been like that since the previous belt change. The timing marks are not exactly ambiguous, so there is no excuse for getting this wrong.
In the end I came round to thinking that the most likely cause of the rather flat performance was a combination of overgearing (1.2 Discovery transfer box and big tyres) and the sheer quantity of extra stuff bolted to the vehicle. While standing back and contemplating all that extra stuff I had an idea of what might be causing the overheating. The vehicle was fitted with a radiator grille muff of the type that blanks off about three-quarters of the radiator aperture and has a roll-up panel in the middle. Sitting right in the middle of the roll-up area were two giant spotlights on an A-bar. On the rear face of the radiator was a large electric fan in a heavy plastic surround. It looked to me as though the airflow through the radiator was pretty much nil.
So I removed the muff and took the vehicle for another test drive. This time I covered about 15 miles of mixed driving varying from town centre to dual carriageway, and the temperature needle settled just below the half-way mark and stayed there. I have never really seen the point of radiator muffs, at least in East Anglia. People say that they reduce engine warm-up time, but this can only really be true if the thermostat is missing or stuck open. Until the thermostat opens there is no coolant flow through the radiator, so blanking off the airflow through it will make no difference.
In conditions of extreme cold a muff can prevent the contents of the radiator from freezing through windchill, but it is very rare in this country that we experience the kind of conditions which a decent antifreeze mix in the cooling system cannot cope with.