Summer car prep works best in April and May, before temperatures climb past thirty degrees and workshops in Banja Luka fill their calendars. Half an hour of work in your driveway plus one workshop visit will save you from an AC failure on the way to the coast. Here is the full list, with a clear line between what you can do yourself and what belongs in the workshop.
This checklist was put together by the Auto Gas Gaga workshop in Banja Luka, in the order it follows with its own customers.
Table of Contents
- Why April-May Prep Matters More Than You Think
- AC Service vs 'Top-Up' (and Why They're Not the Same)
- Cabin Filter - the Forgotten Item That Ruins Cooling
- Tyres - Winters Off, Pressure Up
- Coolant and Oil Level - Two Five-Minute Checks
- Battery After Winter - Why Heat Kills More Than Cold
- Wipers, Glass and Washer Fluid
- Brakes and Undercarriage - What Winter Leaves Behind
- What to DIY and What to Leave to the Workshop
- Frequently Asked Questions
- Related Articles
Why April-May Prep Matters More Than You Think
Winter in BiH leaves a car in worse shape than it looks from the cabin. Salt eats away at the undercarriage and brake discs, the battery is worn down from cold mornings and short trips, the AC has been sitting idle for six months and its rubber seals are slowly drying out. You never noticed any of it because you didn't need the AC and the brakes were still working.
Then comes the first warm weekend and the AC only blows lukewarm. Or you set off for the coast in early July, the car is fully loaded, and only then do you realise your tyre pressures are not set for the load. Workshops are booked half a week out and nobody will fit you in "today".
The April-May prep window serves two purposes: it uncovers what winter left behind while there is still time to fix it without a queue, and it lets you handle all the summer items in a single workshop visit instead of three panicked ones. A separate after-winter checklist lives in Spring Vehicle Inspection After Winter; this article focuses on what needs doing before summer and before a long trip.
AC Service vs 'Top-Up' (and Why They're Not the Same)
This is where most drivers in BiH throw money away. Ads offer "quick AC refills" at a price that sounds like a bargain - until you realise that is usually not a service at all, but a cheap top-up of refrigerant in a system that may be leaking, holding moisture or only half working.
A real AC service means: draining everything out of the system, then vacuuming it and holding the vacuum for at least thirty minutes so every trace of moisture evaporates out, then and only then recharging it with the exact amount of refrigerant specified by the manufacturer. Skip any step and you are filling a system that still contains water and air, and the compressor will not put up with that for more than a season or two.
What a complete AC service covers:
- R134a recharge for vehicles built up to roughly 2017
- R134a recharge with ozone disinfection, if the cabin has unpleasant smells
- R1234yf recharge for vehicles from 2017 onwards (the newer, more environmentally friendly refrigerant)
- R1234yf recharge with disinfection
- Leak detection and compressor condition check
R1234yf is the newer, more environmentally friendly refrigerant used from 2017 onwards. The gas is more expensive and is not the same as R134a. If the mechanic does not check which one goes into your car before charging it, that is a sign to go elsewhere. A cheap "top-up" feels like a saving right up to the point the compressor fails, and a compressor repair costs many times more. For a quote on your specific vehicle, get in touch with the workshop.
A service is recommended at least once a year, especially before longer trips; in Banja Luka vehicles up to five years old are serviced every two years, older ones every year. Before the first hot days, switch the AC on for about twenty minutes and pay attention to three things: is it cooling as well as last year, are there any unpleasant smells, and are there any unusual noises from the dashboard or under the bonnet. If anything is "not quite like before", it is time for a service. For a deeper look at how the AC works, see Car AC: Servicing, Refrigerant Refills and Common Pre-Summer Faults.
A small tip: do not switch the AC straight to the lowest temperature and highest fan speed the moment you start the car. Hitting a cold compressor with a heavy load shortens its life.
Cabin Filter - the Forgotten Item That Ruins Cooling
The cabin filter (pollen filter) sits behind the glove box drawer on the passenger side or under the bonnet, depending on the model. It traps dust, pollen, exhaust particles and fungal spores before they reach the cabin.
A clogged filter does two kinds of damage. First, it reduces airflow - the fan runs at full power but barely anything comes out of the vents, and drivers read that as "the AC is weak" and rush to have it refilled with refrigerant. Second, moisture and organic particles slowly grow mould, so every time you switch the AC on the cabin smells musty.
Replacement is due every 15,000-20,000 km or once a year, whichever comes first. On most vehicles a driver can do this in fifteen minutes with a YouTube tutorial; if you would rather not, we can do the filter and fit it for you at the workshop.
Signs the filter is done:
- Weak airflow even with the fan on maximum
- Musty smell when the AC or heating comes on
- More dust than usual on the inside of the glass
- Allergy symptoms getting worse while driving
If the last time you changed it was "I can't remember when", change it now. Half of all "weak AC" complaints are actually just a clogged filter.
Tyres - Winters Off, Pressure Up
First item is swapping winter tyres for summer ones. The legal deadline for when winter tyres are no longer mandatory is 15 April, but there is no rush if temperatures are still swinging. The rule: switch to summer tyres once night-time temperatures stay reliably above 7 degrees Celsius. A summer tyre on morning ice is more dangerous than it looks, and a winter tyre in summer heat wears out fast and brakes worse.
Once you have the winter tyres off, check them before they go into storage: measure tread depth, check for cracks in the sidewall, uneven wear or bubbles, and note the depth down for next winter.
For summer tyres, check the same things: tread depth at least 3 mm if you are planning a trip to the coast (the legal minimum is 1.6 mm, but in the rain on the motorway the difference between 1.6 and 3 mm is the difference between sliding and stopping). Also check the DOT marking - if a tyre is older than six years, the rubber compound has dried out regardless of how the tread looks.
Pressure is the bit most drivers forget. The table of specified values is on the driver's door jamb, on the fuel filler cap or in the manual. The table usually has two columns: pressure for normal driving and pressure for full load (five passengers plus luggage). When you set off for the coast with the family and suitcases, you bump the pressure up to the "full load" values, usually 0.2-0.4 bar higher.
Always measure on cold tyres, before driving, not at a petrol station after a hundred kilometres. Check once a month and always before a long trip; don't forget the spare. More on this in What to Check on Your Car Before a Long Trip.
Tyre wear is diagnostic. Chewed inner edges mean the alignment needs adjusting; a polished centre strip means they were overinflated; worn outer edges mean they were underinflated. Sort it out before the season, otherwise you will burn a new tyre in a single summer.
Coolant and Oil Level - Two Five-Minute Checks
Coolant keeps the engine at operating temperature when the outside heat hits 38 degrees. If the level is low, the engine will overheat in traffic on the approach to Neum - and there is nothing to fix by the roadside there.
The check takes five minutes: the engine must be cold (a hot cap can blow coolant out), look at the translucent reservoir (expansion tank) - the level must sit between MIN and MAX. If it is below MIN, top it up with coolant of the same colour and type, never water alone.
If the difference is big or you topped it up a couple of months ago and it is below MIN again, the system is losing fluid somewhere - joints, hoses, radiator or cylinder head. That goes into the workshop; it is not fixed by topping up. On colour: green/blue is the classic standard; pink, yellow or orange are the long-life formulas (G12, G13) and do not mix with the old ones.
Oil is checked on the dipstick while the engine is warm but switched off, on a level surface. The level has to sit between the two marks, ideally closer to the top one. Colour - light brown is normal, black like ink means it is time for a service. If you are close to your change interval (usually 10,000-15,000 km for petrol engines, 7,000-10,000 km for diesels), better to do a small service now than to break down on the road. A detailed schedule lives in When to Change Oil, Filters and Fluids.
Battery After Winter - Why Heat Kills More Than Cold
A common misconception: the battery dies in winter. It is true that you first notice weakness in winter, because a cold engine demands more current to start. But a battery actually wears out fastest in summer: high temperatures under the bonnet speed up electrolyte evaporation and corrosion of the internal plates. Winter simply exposes what summer already destroyed.
After winter, before summer, check the battery on three points:
- Resting voltage - with a voltmeter, should read 12.4-12.7 V when the car has been standing for hours; below 12.2 V is an alarm
- Voltage under load - with a workshop tester, shows how much current the battery can actually deliver
- Terminal condition - white or green powder (corrosion) reduces conductivity and makes starting unreliable
If the battery is older than 4 years and there were mornings this winter when the car turned over sluggishly, do not wait for it to die in the middle of the summer rush. For a load test and replacement, drop by the workshop. More details in How to Tell Your Battery Is on the Way Out.
A small point: if you drive short trips around town (up to 10 minutes per start), the alternator does not have time to refill the battery for what the starter pulls out. Short trips + winter = a battery that is done in three years instead of five.
Wipers, Glass and Washer Fluid
Small items that make the difference when the first summer downpour catches you on the way to the coast. Wiper blades get worn down over winter by ice and salt, so in summer they smear dust and insect remains instead of clearing them. A swap takes two minutes. The gap between the cheapest blades and a mid-range one is dramatic; the cheapest shred their rubber within a month.
Clean the outside of the glass with a product that removes mineral deposits from rain. On the inside, especially the windscreen, many drivers never clean it - and then at sunset they can't see anything through the glare. Alcohol glass spray plus a microfibre cloth beats anything else.
Top up the washer fluid reservoir - swap the winter alcohol-based one for a summer fluid with insect remover. The cheapest safety upgrade you can make to the car.
Brakes and Undercarriage - What Winter Leaves Behind
Salt and moisture over winter cause two kinds of damage you cannot see from the cabin. The first is corrosion on the brake discs - a thin layer of rust wipes off on the first drive, but deeper rust means the pads will not brake evenly. The second is corrosion of the undercarriage, exhaust system and brake lines.
Wash the undercarriage under pressure at a proper car wash, not just the bodywork, the moment the freezing risk has passed. That saves you from holes in the exhaust silencer and brake hoses giving way years down the line.
Brakes need to be listened to. If they squeal under light braking, pop and click, or the steering wheel vibrates when you brake hard from speed, the discs and/or pads are ready to be replaced. We cover the warning signs in How to Tell When Your Brakes Need Servicing. This rarely gets more than a couple of weeks of ignoring without becoming a motorway risk in summer.
Suspension and shock absorbers - winter potholes have given them a beating. If you hear knocks over bumps or the steering pulls to one side, drop by the workshop for a suspension check.
What to DIY and What to Leave to the Workshop
| DIY (at home, 30 minutes) | Take to the workshop |
|---|---|
| Check tyre pressure (all four plus spare) | AC service (vacuum, recharge, leak detection) |
| Replace the cabin filter (with a YouTube clip) | Full undercarriage and brake inspection |
| Check coolant level in the expansion tank | Battery load test and replacement |
| Top up washer fluid | Diagnosis of weak AC or unusual smells |
| Check oil level on the dipstick | Winter-to-summer tyre swap (if you don't do them at home) |
| Replace wiper blades | Brake pad or disc replacement |
| Visual tyre inspection (tread, damage) | Pressure-wash the undercarriage |
| Clean glass inside and out | Suspension alignment check |
Need a hand with the summer inspection? Book an appointment online or drop into the workshop - AC service, filter replacement and undercarriage check can be done in a single visit.
Frequently Asked Questions
How much does an AC service cost in BiH in 2026?
The price depends on the refrigerant type (R134a for older vehicles or R1234yf for newer ones, from 2017 onwards), on the scope of work (just a recharge, recharge with disinfection, or a full service with leak detection) and on the actual condition of the system. For a quote on your vehicle, get in touch with the workshop. Stay away from offers like "quick AC refill" at suspiciously low prices - that usually means nobody is checking for leaks or pulling a vacuum, so the compressor ends up ruined within a season or two.
When is the best time to do summer prep?
Mid-April to mid-May. Earlier than that, the night-time cold has not quite passed so there is no rush to take the winter tyres off. Later than that, workshops in Banja Luka, Sarajevo and Mostar are full because everyone else was waiting for the first warm day. The April-May window gets you a workshop slot in three days instead of two weeks.
Can I check tyre pressure myself?
Yes, a pressure gauge is an affordable bit of kit and it lasts for years. Check on cold tyres, before driving. Wrong pressure affects fuel consumption, cornering stability, braking distance and tyre wear. When you set off for the coast with the family and luggage, you raise the pressure to the "full load" values from the door-jamb table - they are usually 0.2-0.4 bar higher than the normal figures.
Why does the cabin filter affect the AC?
A dirty cabin filter reduces airflow through the ventilation. The fan runs, the compressor runs, but hardly any cold air comes out of the vents - and that feels like "the AC is weak" when in fact the problem is the filter. In a damp filter, mould and bacteria grow and produce unpleasant smells. The swap takes fifteen minutes and is the best-value item on the whole summer list.
How often should coolant be changed?
Standard green/blue coolants are changed every 2-3 years or 60,000 km. Long-life ones (G12, G13, usually pink or yellow) last 5 years or 150,000 km. If the level keeps dropping and you keep topping it up, the system is leaking somewhere - joints, hoses, the radiator or, in the worst case, the cylinder head. Constant topping up without finding the cause ends with the engine overheating on the road.
Do I have to take the winter tyres off if I only drive around town?
Yes. A winter tyre in summer heat has two problems: it wears out faster (the rubber compound is softer and cracks in the heat), and it brakes worse because the tread pattern is designed for ice and snow, not for a hot dry surface. On top of that, in BiH it is a legal requirement to switch to summer tyres after 15 April under most conditions. If you don't plan to leave the city, you will still burn through the tyres in a single season instead of getting three or four years out of them.