Cooling System Summer Check: Stop Your Car Overheating in Liverpool Traffic

Overheating is one of the most common phone calls we take in the warmer months. The car sits in traffic on the Strand or crawls along Queens Drive on a hot afternoon, the gauge climbs, and the driver pulls over with steam coming from under the bonnet. It usually starts small — a slow coolant leak, a tired thermostat, a fan that no longer kicks in — and ends with a tow truck and a much bigger bill.

The cooling system gives plenty of warning before it gives up, and most issues are cheap to fix if caught early. A summer car service at our Wavertree workshop covers the lot: coolant level and condition, hoses, radiator, water pump, thermostat, fan and cap pressure. Here is what each part does and the warning signs that something is on its way out.

Why summer is hard on the cooling system

Your engine produces an enormous amount of heat. The cooling system has one job: keep it at its ideal temperature, around 90°C, in any weather. Coolant (the pink, blue or green liquid in the expansion tank) circulates through the engine, picks up heat, passes through the radiator at the front of the car, and dumps that heat into the air flowing past. In summer, ambient air is hotter and stop-start traffic means hardly any air is moving through the radiator naturally — you are relying on the electric cooling fan. Any weakness — a weak coolant mix, a tired fan, a slightly leaky hose — shows up far faster in July than in January. If your dashboard ever flashes a temperature warning, do not keep driving. Pull over, call us, and ask about free collection across Liverpool — it is cheaper than a new engine.

Coolant, hoses, radiator and the water pump

Coolant is a mix of water and antifreeze, usually around 50/50. The antifreeze stops the water boiling in summer, freezing in winter, and contains corrosion inhibitors that protect your radiator, water pump and engine block. Those inhibitors wear out — most manufacturers recommend a change every 4–5 years. If yours is rusty brown, cloudy, or has bits floating in it, the system is corroding from the inside. A diagnostic check and coolant flush is a fraction of the cost of a new radiator.

Check the level in the expansion tank when the engine is fully cold. It should sit between MIN and MAX. Never undo the cap on a hot engine — the system is pressurised and you will get a face full of boiling coolant. If you are topping up regularly, you have a leak. Different manufacturers use different coolant specifications and mixing the wrong types can gel the lot up — if you are not sure what yours takes, ring us.

Hoses are the thick rubber pipes between engine, radiator and expansion tank. Squeeze the top hose when cold: firm but slightly springy is fine, rock-hard or mushy is not. The radiator is the wide finned panel at the front — look for green, pink or rusty staining on the face, which is dried coolant from a leak. The water pump pushes coolant around the system; on many cars it is driven by the cam belt (the toothed rubber belt that keeps the engine timing in sync), which is why we always pair a water pump and cam belt replacement — very little extra labour and saves a second strip-down later.

Thermostat, fan and warning signs to never ignore

The thermostat is a small valve that stays shut until the engine warms up, then opens to let coolant flow through the radiator. Stuck closed and the engine overheats almost immediately, especially in traffic. Stuck open and it never reaches proper operating temperature — the heater is feeble and fuel economy drops. Either way, a cheap part if caught early.

The electric cooling fan kicks in automatically when the coolant gets too hot, usually around 95°C. You can hear it whirring up when the car has idled in traffic. If you sit in a jam and notice the temperature climbing without the fan running, get it checked. Bad fan motors and corroded fan relays are very common and almost always the reason for the classic summer overheat-in-traffic scenario.

Warning signs: a gauge climbing higher than usual, a sweet smell from the engine bay (coolant has a distinctive smell), white steam from under the bonnet, the heater blowing cold when it should be warm, or coolant pooling under the parked car. Any one of those needs investigating before it becomes a head gasket job. The RAC’s overheating engine advice is worth a read for what to do at the roadside.

Booking a check before the summer mileage starts

If the car has not had a coolant change in 4–5 years, if you have noticed any warning signs, or if you are heading off on a long summer drive, book a cooling system check. We pressure-test the system to find leaks too small to see, test coolant strength with a refractometer, check thermostat operation, test the fan and relay, and look at every hose and joint. Most checks take under an hour. If a fault is found we give a no-obligation quote and tell you what needs doing now versus what can wait. Same-day repairs on most jobs, free collection and drop-off across Liverpool, all makes and models including light commercials. 20% discount for emergency services and armed forces. The government’s hot weather driving advice makes the same point: pre-summer prep beats roadside recovery every time.

Frequently Asked Questions

How often should engine coolant be changed?

Most manufacturers recommend a full coolant change every 4 to 5 years, or every 50,000 to 60,000 miles. Long-life coolants can last longer, but the corrosion inhibitors still wear out. If your coolant looks brown, cloudy or has debris in it, it is overdue regardless of age.

Can I top up coolant with plain water in an emergency?

Yes, as a short-term measure to get you home or to a garage. Use clean tap water and only top up when the engine is fully cold. Have the coolant properly flushed afterwards — plain water lacks the corrosion inhibitors.

Why does my car only overheat in traffic, not at speed?

Almost always a cooling fan or fan relay fault. At speed, plenty of air is forced through the radiator. In traffic, the car relies on the electric fan. If it does not kick in, the temperature climbs. One of the most common summer faults and usually a same-day fix.

Is a small coolant leak safe to drive on?

Not for long. A small leak will eventually empty the system, and once coolant drops too low the engine overheats — potentially warping the head or blowing the head gasket. If you top up more than once a month, get it diagnosed.

Do you supply and replace water pumps and radiators?

Yes — water pumps, radiators, thermostats, hoses, expansion tanks, fans and full coolant flushes are all standard work. Quality OE-equivalent parts, no-obligation quote, same-day on most jobs. Free collection across Liverpool.