Tractor: the checks to make before a long lay-up

A tractor that sleeps doesn't wear out, it deteriorates. That isn't the same thing, and it's what makes a long lay-up so misleading: nothing moves, nothing heats up, nothing rubs, and yet the machine comes back out with a blocked fuel filter, a dead battery, two deformed tyres and a chewed-through loom. Not one of those failures would have happened if the machine had been working.

A long lay-up means six months to two years: a back-up tractor on a farm, a compact belonging to someone who only uses it in autumn, a machine kept in reserve, an estate waiting to be settled. The routine isn't the one you'd follow for a normal three-month winter storage, because three mechanisms change scale with time: fuel degradation, internal corrosion from condensation, and wildlife.

A long lay-up isn't a winter storage

Over three months, a good many problems never get going: the diesel stays serviceable, the battery holds up if it's healthy, the tyres come back into shape after a few hundred metres. Past six months, every one of those items tips over.

The other difference is psychological. With winter storage you know you'll be getting the machine out again in spring. With a long lay-up the restart date is vague, so jobs get put off. That's exactly why everything has to be done before you shut the door. Our tractor winter storage checklist covers the short case; what follows is what you add beyond it.

Diesel degrades, and the biofuel content doesn't help

Ordinary road diesel commonly contains a proportion of fatty acid methyl esters — up to around 7 % in many markets, though the blend varies from one country to another and with the season. These esters have two awkward properties in storage: they absorb more moisture than mineral diesel, and they make an excellent growing medium for micro-organisms.

The usual figure quoted is a stability of 6 to 12 months for well-stored diesel, and rather the bottom of that range as soon as there's biofuel in it and a tank that breathes. Beyond that come gums and sediments, which block the filter at the first start-up, then microbial contamination, which develops at the interface between condensed water and fuel and produces black gelatinous sludge. Cleaning out a contaminated system completely is a full-blown job.

Three measures, in order of importance:

• Drain the water separator or pre-filter before you lay the machine up.
• Add a stabiliser beyond six months, at the stated dose. It's a preventive product: it won't rescue fuel that has already degraded.
• Add a biocide if the machine has already had a contamination, or if the tank takes in moisture.

Tank full or empty: the trade-off is real

The classic rule says store it with a full tank, to eliminate the air volume and therefore the condensation. That holds good up to about a year: you fill to 90 or 95 %, leaving room for expansion.

Beyond that the trade-off shifts, because a full tank also means a lot of fuel getting old. For more than eighteen months, it becomes reasonable either to drain tank and lines, or to put in fresh fuel with stabiliser and biocide knowing you'll refilter on waking it up. What you must not do is leave half a tank of old diesel standing for two years: plenty of air and plenty of tired fuel, the worst combination there is.

The systems you don't leave as they are

• Engine oil gets changed before the lay-up, not after. That's the opposite of what many people do, and it's the most important point on this list. Used oil is loaded with soot, condensates and acidic compounds from combustion. Through the months of standing, that acidity works away without ever being neutralised by a return to operating temperature, and attacks the bearing shells and journals. Changing it beforehand, with a new filter, costs the price of an oil change and removes the problem.
• Coolant gets checked with a refractometer. You look at the freeze protection point, often between -25 and -37 °C depending on the dilution. But the issue on a long lay-up is the corrosion inhibitors, which deplete with time even without running: a coolant that still protects against freezing may have stopped protecting the liners and the water pump. Beyond three or four years, replace it before you close up.
• The hydraulics breathe through the breather, so they take in moisture like the fuel tank does. A milky appearance means water is present. The filter gets replaced on waking rather than beforehand, so you don't leave a new element soaking for months.
• Cylinder rods get retracted. An extended chrome rod is an exposed rod: condensation, dust, pitting corrosion, then a scored seal and a leak. Retract everything that can be retracted, and grease generously whatever has to stay out.
• Don't leave the parking brake on for months. The linings stick to the drums or discs, and tear when you release them. Chock the wheels and leave it in gear instead.

Tyres: the deformation costs more than the pressure

An agricultural tyre works at low pressure, often between 0.8 and 1.6 bar depending on load and carcass. Left standing for months on the same point, it takes a flat spot: over a few weeks it disappears as you drive, over a year it can become permanent, with sidewall cracking where the deformation was.

Three levels of response, depending on the duration:

• Up to six months: inflate to 20 to 30 % above the usual working pressure, without exceeding the maximum pressure marked on the sidewall, and move the machine a few metres every two months to change the bearing point.
• Beyond six months: put the axles on stands, wheels off the ground. That's the only solution that genuinely removes the problem.
• In every case: lay down boards rather than leaving prolonged contact with damp concrete, and don't put a brushed electric motor or a welding set in the immediate vicinity. Those produce ozone, which crazes rubber.

Bring the pressures back to working values before the first use, not after: working under load on over-inflated tyres damages the tread and the soil. The load and pressure reference points are in our article on tractor tyre pressure and wear.

Rodents: the cost nobody budgets for

This is the number one source of damage on a machine that sleeps for a long time, way ahead of anything mechanical. A chewed loom is rarely repaired cleanly, and replacing it runs into hundreds of pounds, sometimes over a thousand with labour and the diagnostic time needed to find the broken wire. What protects it:

• Block the openings: exhaust outlet, air intake, cab apertures. Use a visible red rag and note the blanking on a label hung on the steering wheel, or you'll start up with it still in place.
• Remove anything that feeds them over a wide radius: seed bags, feed, improvised nesting material.
• Prefer physical barriers and traps to poison baits. A rodent that dies inside a conduit creates another problem.
• Open the bonnet once a quarter and inspect. Five minutes that spare you the discovery of a nest twelve months later.

Battery: removed, charged, checked

A lead-acid battery self-discharges at around 3 to 5 % a month at rest, more if it's dirty or if the circuit draws current on standby. Below about 12.4 V, sulphation starts and becomes irreversible with time.

The protocol: take the battery out, clean the terminals, charge it fully, store it dry and frost-free, then recharge every two to three months or leave it on a trickle charger. One thing that surprises people: a charged battery resists freezing down to very low temperatures, whereas a discharged battery can freeze at around -10 °C, which destroys it and sometimes cracks the case.

Check the resting voltage before refitting it. Settled at 12.6-12.7 V it's full; at 12.2 V it's half charged and won't turn over a cold diesel. The rest of the diagnosis is in our article on tractor starting problems.

What the duration changes

Waking it up, in order

The temptation is always to turn the key first. That's the surest way to turn a deposit in a filter into an injection failure.

1. Cold inspection, bonnet up: rodent traces, nests, chewed cables, hardened or cracked hoses, leaks on the floor.
2. Remove the intake and exhaust blanks, and check the reminder label.
3. Levels and draining: engine, coolant, hydraulics, drain the fuel water separator until clear fuel comes through.
4. Battery refitted, charged, terminals clean and greased.
5. Tyres back to working pressure, machine lowered off the stands.
6. Greasing at every point, then a visual check of steering and brakes.
7. Starting: full glow cycle, idle for five to ten minutes with no load, temperature brought up progressively.
8. Work every cylinder to its stops two or three times to purge the air and rebuild the oil films, then replace the hydraulic filter if the lay-up ran over a year.
9. Low-speed test on flat ground: brakes, steering, PTO unloaded, before applying any load.

What really decides the condition of a tractor when it wakes up is two jobs done before the door closed: the engine oil change and getting the tyres off their load. Everything else can be caught up; those two can't.

For the values specific to your machine — capacities, hydraulic oil viscosity, coolant replacement interval, wheel torques — L'Atelier's assistant gives the manufacturer's data from the make, model and year, rather than having you apply a segment average to a machine that isn't one.