Monsoon Car Care: What Actually Matters

The monsoon is harder on cars than the heat is, and the failures it causes are mostly preventable with an afternoon of attention. The problem is that the components involved are the ones nobody thinks about until the moment they are needed.

Tyres come first

Everything about wet-weather safety runs through the tyres, and tread depth is the variable that matters most. Tread does not provide grip; the rubber does. What tread does is give water somewhere to go so the rubber can reach the road. As depth reduces, the volume of water the tyre can clear per second falls sharply.

The legal minimum in India is 1.6mm, marked by moulded wear bars in the main grooves. But wet braking distances degrade well before that. Somewhere around 3mm is where a sensible person replaces tyres if the monsoon is coming. The difference in stopping distance from 80 km/h on a wet road between a 3mm tyre and a 1.6mm one is measured in car lengths.

Check pressures too, and check them cold. Underinflation makes the tyre flex and the centre of the tread lift slightly, which reduces the contact patch exactly where you need it. The correct figure is on a sticker in the driver door frame, not on the tyre sidewall.

Wipers and glass

Wiper blades are consumables with roughly a one-year life in Indian conditions, because UV and heat harden the rubber. A blade that smears, chatters or leaves an unwiped band is finished, and replacing a pair is among the cheapest safety improvements available.

Clean the glass properly before you judge them. Much of what looks like wiper failure is actually a film of road grime and oily residue on the windscreen, which no blade will clear. Glass cleaned with a proper glass cleaner, inside and out, transforms night visibility in rain.

Top up the washer bottle with actual washer fluid rather than plain water. Water alone will not shift the oily film that traffic throws onto the screen, and in the monsoon you will get through more of it than you expect.

Brakes behave differently when wet

Wet discs give reduced friction for the first application, which is why a light touch on the brakes after driving through water is a useful habit: it wipes the film off and dries the surface. This matters more than people assume on the approach to the first junction after a flooded stretch.

If your brake fluid has not been changed in more than two years, do it before the season. Brake fluid absorbs moisture from the air over time, and water in the fluid lowers its boiling point, which is the mechanism behind a pedal that sinks to the floor under sustained heavy braking. It is a cheap job that almost everybody skips.

Check the drains

Cars have drainage channels most owners never see: at the base of the windscreen under the plastic scuttle panel, in the sunroof rails if fitted, and in the door bottoms. They block with leaves and grit, and when they do, water backs up and finds its way into the cabin.

A damp footwell is not merely unpleasant. Modern cars route wiring looms and control modules under the carpet and beneath seats, and water there causes electrical faults that are expensive and maddening to trace. Clearing a drain is a five-minute job with a length of garden wire; finding an intermittent electrical fault caused by one is not.

Sunroof drains deserve special mention because a blocked one typically appears as water dripping from the headliner or the A-pillar, which people misdiagnose as a leaking seal.

Electrics and lights

Damp finds weak connections. Check that all exterior lights work, including both brake lights and the reversing lights, because visibility in heavy rain depends on being seen at least as much as on seeing. Condensation inside a headlamp housing means the seal has failed and moisture is getting in, which shortens bulb life and eventually corrodes the reflector.

If your car has an accessory fitted by someone other than the manufacturer, damp weather is when a poor installation announces itself. Spliced joints wrapped in tape corrode, and the resulting faults appear in places that seem unrelated.

Standing water: the one rule that matters

Do not drive into water when you cannot see the road surface through it or judge its depth. That is the whole rule, and almost every seriously damaged car in a flooded underpass belonged to someone who thought it looked shallow enough.

The specific danger is hydrolock. Engines compress air, and air is compressible. Water is not. If water is drawn into the air intake and reaches a cylinder, the piston attempts to compress an incompressible fluid on the way up, and something has to give. Usually that means a bent connecting rod, and that means an engine rebuild.

If your engine stops while in water, do not attempt to restart it. Restarting is what converts water in a cylinder into a destroyed engine. Have the car towed, and tell the workshop it was in flood water so they check before cranking it.

If you must cross shallow water, go slowly and steadily in a low gear without changing gear, keeping light pressure on the accelerator to maintain exhaust pressure. Then dry the brakes afterwards as described above.

After the season

Wash the underbody once the rains ease. Road water carries grit and salts that sit in the seams and wheel arches and accelerate corrosion, and the underside is the one part of a car that never gets cleaned incidentally.

Check the cabin filter as well. Damp plus organic debris is how evaporators start to smell, and a filter that has spent three months wet is usually ready to be replaced.