How to assess a Discovery 1

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Discovery_1_Assessment Ground-breaking profile – unique for it's time : credit: © JLR
Whether buying a Disco 1, or keeping your own in top condition, essential checks need to be made, explains Ed Evans

Elsewhere on our site you’ll find Dave Phillips’ comprehensive buying guide to this immensely practical and owner-friendly truck. And here is the technical supplement that shows how to assess a potential purchase, with a view to buying a good one, or understanding the realities of buying an example that needs some work or a complete restoration. And if you’re lucky enough to already own a Discovery 1, use this guide to continually assess its condition to keep it on top form.

We’ll deal with the checks in stages: the pre-road test checks, the road test itself and, if the vehicle passes scrutiny, the final detailed checks. But first, let’s take a browse around exactly what a Discovery 1 is.

 

This is what you're getting

Space, comfort, practicality and DIY maintenance

That uniquely-shaped body uses many aluminium alloy panels supported on steel structures with steel inner wings. So, expect the usual galvanic corrosion between dissimilar metals. But even without that, the aluminium and steels are very capable of corroding on their own, especially the inner sills and underfloor and the load space floor, all of which need close scrutiny. Rusted sills and floor can be very expensive to restore properly.

The steel chassis (not to be confused with the Discovery II’s reputation for falling out onto the road) is relatively long lasting but, given these trucks can be up to 30 years old, it remains important to expect corrosion problems.

The running gear: transmission, axles, brakes and suspension are all tried and tested parts and assemblies that are simple to work on and well provided for on the aftermarket parts and repair circuit.

2.0 Mpi petrol was also fitted to the Rover SD1

The 200 and 300Tdi diesel engines can still be running well after 200,000 miles. There’s little to choose between the two; the most significant factor being that some engine parts including cylinder heads may be getting thin on the ground for the earlier 200Tdi. Early cam belt alignment problems and subsequent engine failures with the 300Tdi, have all been repaired now and are no longer a concern. Then there’s the Rover V8 versions: carburettor or injection fuelled, they’re both good – thirsty, of course, but smooth and quiet and they’ll pull the Disco around at a respectable pace even with an auto gearbox (the diesel autos are sort of meditational, they won’t be rushed). The rare 2.0-litre four-cylinder petrol version lacks the low-down torque of the diesels, which is a disadvantage off-road and for towing, but offers a curiosity factor.

200Tdi (top) and 300Tdi are instantly recognisable by their different thermostat housings and the position and colour of the engine oil dipsticks

So, that’s what’s on offer. The trick is in finding a good example or, at least knowing what sort of a mess you’re buying so that repair and restoration can be factored into the overall cost. And a bad one is eminently restorable and is a worthwhile project that can be tackled by any good DIYer with the right workshop manual and, perhaps, good welding skills or a local garage than can take on some of the work.

 

Assessing a potential purchase

The most important part of this section is the road test, but, before driving, we need to know the vehicle is safe and legal. We (not the owner) are legally responsible for the road worthiness of the car we test drive. So these are the first checks to be made – and they need to be done in any case before parting with cash.

 

Road worthiness​​​​​​

Ask the owner to switch on all lights, indicators and hazards while you check them outside the vehicle. Check the horn and the wipers work. Rock the steering wheel while noting the road wheel moves without too much free play. Check all four tyres are legal. Check the driver’s seat is secure and cannot move forward or back without using the switches or levers, and confirm the seat belts latch, release, and lock when pulled.

Under the bonnet, check whether the engine is warm or cold. It’s important to know the engine starts from cold so, if the seller has pre-warmed the engine, come back next day to try it cold. Check the oil and coolant levels (coolant only with the engine cold) and make a note of the exact levels at this stage. Dirty engine oil on the dipstick suggests poor servicing, though diesels’ oil soon turns black anyway. Dirty or old thick oil on a V8 over an extended period may have caused camshaft wear.

Mpi and diesel cambelts should be changed every 96,000 and 72,000 miles respectively (six years if sooner). If no proof, factor in the cost of the work​​​​​​

Start the engine, noticing any reluctance to fire and checking for exhaust smoke when it does fire. A little grey smoke from a diesel (or a petrol on choke) when starting isn’t a concern; more than a puff of black smoke from a diesel is. If there’s blue smoke from a diesel or Mpi the valve seals may need renewing, or the engine may need a rebore, especially if the top of a diesel is wet and oily.

Inside, switch the ignition on and check that the dashboard warning lamps all illuminate and then extinguish. It’s okay if the ABS warning lamp stays on until the vehicle moves away. So we’ve now confirmed the vehicle is probably legal to drive.

 

Test drive

As you pull away, quickly get a feel of the brakes and steering. If in any doubt, stop. If all’s well, listen for clunks when pulling away and check the manual gear lever moves and engages freely and that an auto picks up smoothly and changes correctly as you build up speed. When decelerating, the manual should not jump out of gear (try in each gear) and the auto should drop down without jerking or over-revving. Check reverse, too, and confirm low range and diff lock are working.

When cornering, check the steering feels precise. There should be no steering vibration or wobble, even when you deliberately aim for a pothole as part of the test. Any problem here may need the front swivel housings re-shimming or new swivel bearings (assuming the wheel bearings aren’t loose). Wandering or imprecise steering may be due to worn or loose bushes in the Panhard rod – not to be confused with over-responsive steering which is likely a hydraulic issue.

On a quiet road with no other road users, especially behind you, try the brakes with increasing intensity. The truck should pull up dead straight with no pressure needed on the steering wheel and no locking up of the rear wheels.

Now try accelerating through the gears. A slight chassis twitch (often instinctively countered by slightly moving the steering wheel) suggests worn rear radius arm bushes are allowing some movement of the rear axle. It’ll probably be detectable when suddenly releasing the accelerator, and suddenly accelerating, too. The fix is cheap and easy, but it could more seriously be caused by corrosion in the rear axle bracket where the radius arm is attached. The rear axle A-frame joint is another possibility, though less likely.

Electronic Diesel Control (EDC) on later 300Tdi automatics is a basic system that’s reliable and efficient

During this acceleration and deceleration, keep an eye on smoke from behind. An acceptably worn engine may put out a little grey smoke on acceleration, though it’s not ideal, whereas black or white smoke suggests fuelling problems that might need diesel injectors servicing and/or a more costly fuel injection pump overhaul. Smokey carburettor V8s may need a carb reset or overhaul, but diagnosis can be tricky on an Efi V8.

While driving, you don’t want to hear rattles from the engine (a bit of tappet noise when cold may just need adjustment, though it could need a camshaft and cam followers on a V8). It’s not going to cause an imminent breakdown, but needs doing. A tinny vibration appearing to come from inside the cab is possibly a fractured bracket on a front wing ahead of the wheel arch (usually nearside), or the wing has corroded at the bracket and broken free. Easily sorted.

The Discovery 1 may feel that it rolls on corners. This is something the driver gets used to and will counter with driving style. Static and dynamic stance should be good – normal driving doesn’t break suspension springs on this off-roader. But if the suspension seems too soft, or there’s instability or front end diving during braking, the cause is likely to be defective dampers (shock absorbers). And if the ride is too firm or twitchy, incorrect dampers may have been fitted.

Unless you’re buying for a specific off-road purpose and understand the implications, avoid vehicles with raised suspension. This can compromise handling and stability, put undue strain on transmission and suspension components, and may cause an insurer to decline cover.

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Poor diesel performance on hills may be caused by blocked fuel filter, weak lift pump, or air ingress via a perforation on fuel pipe under the rear floor

While driving around, keep listening for knocks, whines, rattles and vibrations. Whining may be bearing wear in the transfer box or a differential. Continually check the engine coolant temperature on the gauge – it will rise until the thermostat opens, then drop back a little. Some Tdi engines, especially 200Tdi, run surprisingly cool on the gauge. It’s normal; just confirm that initial rise before the thermostat opens, after which the temperature must stay steady. Try to test the vehicle on a long climb; if it starts to run hot, the radiator or coolant pump may be defective. Try the heater full on and full off, and the blower and distribution duct settings. Get the interior warm, then see if the air conditioning (if fitted) can cool it down quickly. If not, the air con may just need a re-gas, or it could get expensive – never assume a re-gas (£120-ish) will be the answer.

At the end of the drive, rock the vehicle forward and backward slightly using first and reverse gear and listening for an underside clunk from the transmission. It’s a worn transfer gear and/or mainshaft splines, though probably all have been replaced by now with the later type from the R380 gearbox (as fitted to later 300Tdi models), but an early low mileage vehicle may have the problem (a worn A-frame ball joint can cause a similar knock). So, assuming the test drive went well, and she’s a lovely old bus – we’re still far from done yet. It’s time to park up and get even more critical.

 

Bonnet and body

It’s preferable to check this rear floor by rolling the carpet back, if the seller will allow. But the general condition may give an idea of what’s underneath​​​​​​

Switch off, get the bonnet up and use a torch to look around for oil, coolant and fuel leaks. If the top of a diesel is freshly wet with oil, then worry. Check for coolant leaks around the V8’s valley and inlet manifold. A screeching noise during the test drive might be a worn auxiliary drive belt and/or a weak tensioner pulley.

Before getting dirty underneath, check the interior. If any carpets are loose, lift them to check for floor corrosion. If the front carpet is damp, the air con moisture drain may need clearing (easy), but if the moisture is sticky it’s probably coolant (difficult). Drop the rear seats to ensure the release works, then pull the load bay carpet back and check for corrosion of the load space floor. Replacement panels are available to weld in and it’s a regular job.

Looking up, any sagging in the headlining will only get worse, and spoils an otherwise good motor, but it’s all doable, of course. Sunroof? Expect them to leak and, if they don’t, leave them shut or they probably will.

Look for rust and bodged repairs on rear inner arches. Seat belt mounting under carpet can be corroded

Ensure all the doors latch correctly and can be opened from inside and outside, and that the locks work on the key and both fobs. Check the door windows fully raise and lower. Electric window faults could be due to the motor, mechanism jam, wiring break or, quite commonly, a break on the ECU printed circuit board which can be easily identified and re-soldered. Check for wear in the hinges of the driver’s door and tail door by grasping the bottom opening corner and trying to rock it on the hinges.

Corrosion on these aluminium body panels is obvious, but look for pinpricks which might soon expand

Back outside, look around the aluminium body panels for white spot corrosion.
This is difficult to tackle, though it can be controlled and a good body shop can repaint, though without guaranteeing the longevity of the repair. Check the inner wings and wheel arches and associated structures including the panels at the front of the engine bay – all steel and trustworthy, but all fixable – just be aware of how all these costs are adding up. Open the rear side doors and check the visible wheel arch here, and importantly, the not so visible attachment of the seat belt mounting under the carpet (also view from underneath). Examine the windscreen, alpine lights and tailglass rubber seals for splits which look unsightly and let water in.

 

Underside checks

Sill and floor corrosion should be clearly visible from underneath, but further sill corrosion will be hidden behind the plastic sill trim, extending up into the door frames

Complete the body inspection by scrutinising the condition of the inner sills, body mounting points and the adjacent floor sections. Use a strong light and confirm the seller accepts you poking firmly into suspect rust areas. If they won’t, assume it’s rotten, if they do, then go for it and hope it’s solid. On many vehicles this area has been properly repaired, so should be good for years. But don’t be surprised to find an original underside that’s unrepaired and solid – they’re not all bad. The same goes for the chassis – check it all over, but the chassis is generally good on these and there’s reasonable access for repair. The rear crossmember and associated body mounts can be replaced, but it’s a more involved job than on a Defender.

BLUE: Steering pump leaks, track rod and drag link off road damage
GREEN: Check Panhard rod bushes
RED: Damper turret corrosion
ORANGE: Swivels for pitting, oil leaks

BLUE: Radius arms (rear links)
GREEN: A-frame, forward mounts to chassis and rear ball joint to axle
RED: Dampers, condition and state of chassis at top mounting brackets

And so to suspension. If dampers are leaking or rusted they have obviously been on the vehicle too long and a new set (with new bushes) will make the truck feel sprightly. Performance-wise, dampers are usually past their best at around 60,000 miles. Springs, not really a problem unless broken. Bushes can be tested with a pry bar, but any issues here should have shown up on the road test. Nevertheless, have a lever at them all – front and rear radius arms, Panhard rod and A-frame ball joint on the rear axle. While you’re here, check the chassis structure where the A-frame forward brackets bolt onto it, and those rear radius arm brackets on the axle casing that we mentioned earlier.

Knocks and rattles may have been caused by the exhaust system so check its fixing and check its general condition which may be a bargaining point. While underneath, check the brake and fuel lines. Freshly greased propshaft joints might hint at good overall maintenance.

300Tdi coolant can leak from the P-gasket that seals the coolant pump to the engine. Check for a drip and staining at the front left of the engine

Check for oil leaks underneath from the engine, transmission and axles. Sump gaskets can leak on V8s, but can be changed with the engine in position. Steering box leakage may well need a new box, and oil dripping from between the gearbox and transfer box will need the unit removing. Slight oil leaks in general are acceptable norms unless you’re precious about your driveway.

Tyres also give a clue to maintenance. The Discovery is something of a premium machine. Cheap rubber suggests it’s been run on a shoe string (at least lately). Likewise, uneven tyre wear points to tracking, suspension and/or steering faults having been ignored for too long, suggesting a poor maintenance regime, despite any service records.

Look for off-road impact damage to the chassis, steering track rod and drag link, engine sump and auto fluid pipes.

 

Making the decision

Lastly, go back to the engine and re-check the oil level and coolant (only if it has safely cooled and depressurised by now). Compare the levels with those you noted earlier and, if there’s any change, you need to know why.

These are all pointers to what can be expected of a particular vehicle: how reliable it might be, how much work a wrong ’un may need to put right, whether it’s worth having as a restoration project, or whether it’s just a cracking machine that must be bought.

Of course, whatever the condition, there’s always a risk that anything might go wrong the next day. Assess the condition and the risk, and agree a price that’s fair to buyer and seller. A few weeks after purchase you will know your motor well and, if looked after, it’ll be a good truck that won’t depreciate.

 

See more of our expert tech advice here.