What to do when winter ends

There is a moment in March or April when the roads are clear, the salt trucks have stopped, and the entire winter problem appears to be over. It is not, and the reason is a property of salt that most people do not know about.

Why the spring wash matters more than the winter ones

Salt is hygroscopic: it draws moisture out of the air, and salt solution stays liquid well below the freezing point of water. So salt residue left on a car does not dry out and become inert. It keeps finding water, and it keeps whatever it is sitting on damp.

Which means salt left in a wheel arch or a seam in April is still working in July. A humid summer is not a rest period for it; it is eight months of continuous, quiet corrosion, at higher temperatures, which speeds the reaction up.

Do it thoroughly. Underbody rinse, wheel arches, and if the sill covers clip off, take them off — salt gets behind them and stays there. The full salt routine is here.

The inspection worth doing while everything is off

Once the car is clean and the mats are out, spend fifteen minutes looking at things you cannot normally see. This is the cheapest preventive maintenance in the year, because everything you find now is smaller than it will be in October.

• Under the floor mats. Lift them and look at the carpet. Damp carpet or white tide lines mean water has been getting past them, which is the case for walls next year.
• The rocker panels and sills. Run a hand along the bottom edge. Bubbling paint is rust from the inside, and it is always worse than it looks.
• Behind the wheel arch liners. Where the most salt-laden spray goes and where it gets trapped.
• The drain holes. Doors, rockers and sills. Poke them clear with a cable tie.
• The garage floor. Fine pitting near where the front wheels sit is early spalling, and it is the argument for a containment mat next season.

Storing the gear so it survives to next winter

Floor mats

Take them out, hose both sides, scrub the channels, rinse again more than feels necessary, and dry them fully before storing flat. Salt left in the channels dries to white residue and you will think next autumn’s cleaning did not work. The method is here.

The windshield cover

Wash it, dry it completely, store it somewhere breathable. A cover put away slightly damp in a sealed bag is unusable by September, and a mildewed inner face is an abrasive against paint.

The car cover, if you used one

Same, and more carefully, because it is bigger and it holds more water. The drying and storage detail is here.

Tire chains

Rinse the salt off, dry them completely, and store them somewhere dry. Chains rust, and a rusted chain is a weakened one. If you never actually fitted them this winter, this is a good moment to ask whether you genuinely need them.

The battery maintainer

Leave the ring-terminal harness on the car. It is weatherproof, it costs nothing to leave, and it means connecting the maintainer next October is a two-second job rather than a hood-opening one.

Jump pack

Charge it fully before storing, and top it up once over the summer. Lithium cells self-discharge slowly, and a jump pack that has sat untouched from April to November may not have what you assumed.

The one job to do in April rather than October

Underbody coating, if you use a non-drying creeping product.

The conventional wisdom is to apply it in autumn, before the salt starts. That is fine. But applying it in spring, right after the thorough wash, has two advantages: the underbody is as clean as it will ever be, and the product has all summer to creep into seams rather than being asked to do it in December.

It is also a far more pleasant afternoon on ramps in April than in November. The DIY method is here.

And then note what did not work

While it is fresh: which mat overflowed, which cover blew off, which brush you kept reaching past for something else. That list is what makes next October’s preparation better than this one.