Your questions answered: Wipers and wheel bearings

Wiper sweep

I was hoping you may be able to help me with a wiper problem on my 1987 Defender. The wipers work normally, but are not sweeping the full screen. They need to come down another 10cm at the bottom of the sweep towards the bonnet. I saw your article where you replaced the cable and wheel boxes and I am keen to know if this is likely to fix my problem.

I have changed the crank gear in the wiper motor and that hasn’t made any difference. It is 115-degree, but I see there is a 140-degree version for later models which looks like it will fit. Even if the issue is a worn wheel box, is this likely to provide a fix by just increasing the sweep of the wipers? I would prefer not to take the dash apart if possible.  Robin

After removing dashboard parts, the assembly is easily accessed. Then the internal cable (or rack) can be renewed and the outer tube (blue) retained

Martin Domoney replies: One symptom of worn wheel box gears is lack of travel in the wiper arms, which also manifests in them parking too high on the windscreen. I wouldn’t change your current drive gear for a 140-degree version without first checking for excessive wear in the drive gears and cable.

Each wheel box is released from the bulkhead by removing the outside drive spline and spindle nut. The two inner nuts are removed to dismantle it from the drive cable assembly

If you lift one wiper arm off the screen and check for slack in the other, it should be fairly obvious if the mechanism has excess play. If the arms are tight with minimal movement, then it may well be that the drive gear needs changing. If there’s slack in the arms, I’d look at replacing the wheel boxes and cable. You’ll need to at least remove the dash top in order to do this, but it’s a simple job.

TDI oil burner

My Defender 300Tdi seems to be using a lot of oil. This has become progressively worse over the last year or so. Before this, it’s always gone between services without any need for topping up.

There is no oil mist blowing from the top of the engine, even when I remove the oil filler cap, and the engine is nice and clean, so I guess it’s not down to engine wear, but more like some developing internal defect. It starts and drives perfectly normally and there are no engine noises, but it has become a bit smoky, especially blue smoke on first starting up in the morning when the engine is cold. Gill Robertson

Ed Evans replies: You don’t say how many miles the engine has covered, though it’s not unusual for a Tdi to have covered 150,000 miles without excessive engine wear. A cylinder compression test would give a basic indication of the condition – for example, if all cylinders have low reading there is the possibility the cylinders are worn, whereas a single low reading would suggest an isolated defect.

There is a possibility of cylinder head gasket failure, allowing oil from the galleries to pass into a combustion chamber to be burnt and expelled through the exhaust. But the main clue is the excessive smoke on cold starting. This suggests wear of the valve stem oil seals. When the engine cools down, oil at the top of the engine can leak past defective seals and accumulate in the cylinders. Then, when the engine is started up, this oil is burnt in the combustion chamber and expelled from the exhaust as blue smoke.

Either way, the cylinder head needs to come off for investigation and, of course, that means fitting a new head gasket, checking the head face for warping using an engineer’s steel rule and feeler gauges, and examining the general condition of the block and head faces. Closely inspect the gasket and you may see deterioration around an oil gallery hole. Before doing this, it is worth having a compression test done – this may not prove anything, but may be valuable information depending on what you discover.

You’ll need a valve compressor tool to safely release the valve springs to change the valve stem oil seals

Regardless of whether this is the cause, remove the valves, refit with new oil seals and check the springs and valve seat faces in the head and the valve sealing faces. Grind the valves in, or replace them and have the seats in the head machined as necessary. While the head is off, use an inside micrometer to measure the bores for ovality and taper, turning the engine on the crankshaft pulley to move each piston out of the way. Also look for scoring of the cylinders, though this is not likely to be causing your problem, nor is the possibility of defective piston rings – that would have caused blowback when you removed the oil filler cap with the engine running.

Wheel bearing care and test

I’ve just replaced the hub bearing on the rear axle of my Series III. I thought I’d do this because as far as I know, the original bearings were still in there after 80,000 miles and 47 years. Now the job is done, I don’t notice any difference in rear end noise, but I’m glad to know that part of the car is in good condition.

There wasn’t any noise coming from the rear axle hub bearings, so how would I have tested the bearings to see if they actually needed replacement? We also have a Discovery 4 and a Freelander 2, neither of which has required wheel bearings – what is the best way to look after them?  Jos Berner

Ed Evans replies: Strictly, you do need to remove the Series III bearings, or at least the hub, in order to test them. And if you’ve gone that far it makes sense to renew them anyway, given the low price. That assumes you can buy quality bearings though – I have bought new gearbox bearings that weren’t as smooth, and with more play, than the bearings I was renewing; so bad, in fact, that I refitted the originals for a better job. Read the bearing number marked on the side of the race and specify the type from a good bearing specialist.

Traditionally, wheel bearing noise could be detected when cornering. On a right-hand bend, as the vehicle leans to the left and transfers more weight to the hubs on that side, you may hear the noise of worn bearings, which will disappear immediately on straightening the steering. That works well on the front axle of basic vehicles, but is more difficult to detect on the rear of a Series truck.

On later vehicles, it gets trickier because of complexity, especially on independent suspension vehicles. For example, on the Discovery 3 and 4 the advanced
soundproofing and better vibration insulation in the standard suspension bushes largely hide any bearing noise. Front wheel bearing noise on these trucks is more likely to be heard when driving very slowly with the window down; the bearing can be heard creaking as it slowly rotates.

The cornering test just mentioned can be misleading. Again, this applies to the independently sprung vehicles whose four wheels can all be adjusted for toe alignment and camber or, more to the point, can be out of adjustment because of bush wear, off-road and kerbing damage or bad assembly, which can set up tyre vibrations which are pronounced during cornering loads and incorrectly diagnosed as wheel bearing wear.

Not much thinking is required  to assess this SIII rear wheel bearing – the rust tells all. Actually, it felt smooth when rotated, but wouldn’t have done so for long

Loose wheel bearings are not necessarily worn, they may just be out of adjustment. With a wheel jacked off the ground and the chassis supported on axle stands, spinning the wheel can reveal imminent bearing failure if you listen very closely near the hub centre. And by rotating the wheel slowly, you may feel a slight vibration or grating. The latter is sometimes best done with the wheel removed and turning the hub.

Ultimately, the best way is by removing the bearing from the hub and spinning it fast while listening closely in a quiet environment, and also by rotating the inner race by hand while applying axial load and holding the outer race firmly. That should show any roughness (there should be none). And, of course, a visual inspection of rollers, balls and races will reveal cage fractures and corrosion or pitting, all of which mean the bearing is finished. But, as mentioned earlier, by the time you’ve removed the bearings for inspection, you’re going to renew them, anyway.

As regards looking after bearings, in the case of your Series III and any other truck where the bearings can be removed and reset, just clean and regrease them according to the service schedule and keep them correctly adjusted, and not too tight. For later vehicles where the bearings are non-maintainable, avoid hard cornering and unnecessary abrupt changes of steering direction – it’s just a case of driving sympathetically: the more the bearings are loaded, the sooner they wear out.

For more of your questions answered by our experts, visit our How to section.

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