Cooling System Repair in Redwood City When the Gauge Climbs

Your cooling system is deliberately pressurized, usually to somewhere around 15 psi.

That's because raising the pressure raises the boiling point of the coolant well above 212 degrees, which lets the engine run at its designed temperature without the coolant flashing to steam.

It has a consequence people don't expect. A radiator cap that no longer holds pressure will cause overheating on a system where everything else is perfectly healthy.

It's one of the cheapest parts on the car and one of the most commonly overlooked.

It also means never opening the cap on a hot engine. The system is under pressure and it will spray scalding coolant.

Never open the cap on a hot system. The system is pressurised on purpose, which is what stops the coolant boiling at operating temperature. Opening it hot sprays scalding coolant. Let it cool.

Turn the AC off, turn the heater on full, and find a safe place to stop. The heater core is a second radiator, and running it hot buys you real time.

Overheating in traffic but staying cool on the freeway points at the cooling fan, or at something blocking the front of the radiator.

At speed, air is forced through the radiator whether or not anything is working. At a standstill, the only airflow is what the cooling fan provides.

The reverse pattern points elsewhere. Cool in traffic and hot under sustained load usually means restricted flow, a blocked radiator core or a failing water pump.

Aluminum cylinder heads warp when they get too hot.

A thermostat is just a valve that stays shut until the engine reaches operating temperature, then opens to let coolant reach the radiator.

Stuck closed, coolant never reaches the radiator and the temperature climbs fast. That's the dramatic failure.

Stuck open, coolant circulates constantly and the engine never properly warms up. The heater blows lukewarm, fuel economy drops, and the temperature gauge sits low.

That second one rarely gets reported, because nothing feels broken. It's still costing you fuel and putting extra wear on a cold-running engine.

The cheapest part can cause the worst symptom. A radiator cap that no longer holds pressure will cause overheating on a system where everything else is perfectly healthy. It is one of the least expensive parts on the car and one of the most commonly overlooked.

Want it checked? Describe what the car is doing and Five Points Tire will tell you whether it needs cooling system repair or something else. Call 650-365-0280, or send the form and someone calls you back. Request an appointment

A pinhole in a hose or a weeping water pump seal can spray a fine mist onto hot metal, where it evaporates before it ever reaches the ground.

So you lose coolant steadily, top it up repeatedly, and never find a puddle to point at.

A pressure test holds the system at working pressure with the engine cold, which makes those leaks show themselves. It's the fastest way to find something that has no visible symptom.

Coolant can also be lost internally, into the combustion chamber or the oil, and that's the more serious version. Milky oil or sweet-smelling exhaust steam are the signs.

Your heater core is fed from the same loop as everything else, and it sits high in the system.

That means it's the first thing to lose flow when coolant is low or when air is trapped in the circuit.

So if your heater has gone lukewarm and the engine is definitely warming up, don't treat that as a heater fault. Check the coolant level first.

If the gauge climbs, AC off, heater on full, pull over, switch off. In that order.

Then note the pattern before you call. Traffic or freeway, sudden or gradual, with steam or without. That's most of the diagnosis.

We pressure test to find leaks that don't show themselves, and check the pump, thermostat, hoses and cap rather than guessing at the cheapest part first.

Call Five Points Tire on 650-365-0280. If it's overheating now, call before you drive it here, because free pickup on our own flatbed costs less than a head gasket.