australia:car_overheating
car over-heating or losing coolant
Introduction
over-heating your car's engine is a major threat to the engine as continued running of the car threatens blowing a head gasket and very expensive repairs / replacement of the engine
over-heating may just occur due to driving in hilly conditions on hot days with a load, in which case you may just need to give the car a rest for a while and checking everything else is fine including sufficient coolant is present
DO NOT CONTINUE DRIVING if your car's temperature gauge starts climbing above the half way mark as this will increase risk of destroying your engine such as by cracked cylinder heads, pushed head gaskets, or burnt pistons.
DO NOT OPEN the radiator cap when it is hot as this will risk major scald burns
when hot the radiator water should be under high pressure as evidenced by attempting to squeeze the large black radiator hoses
Diagnosing engine over-heating issues
steam or very high temperature gauge into the red
as long as temperature gauge not too high, briefly, while the engine is still running, open the bonnet:
turn the engine off as soon as possible and allow engine to cool down BEFORE attempting to open the radiator cap
check the coolant level in the plastic coolant reservoir
open the radiator cap once it has cooled down and ensure there is adequate coolant level in there as well as in the coolant reservoir
if adequate coolant but temp gauge goes very high within 15 minutes of driving:
if coolant level in reservoir is adequate, check if the lower coolant hose is cool when engine is VERY hot as this suggests a faulty thermostat
engines have a valve-based thermostat that determines and regulates coolant inflow so that the engine operates at an optimal temperature and does not overheat. The thermostat should be closed when the engine is cold and not running. Regulation of water by the thermostat prevents engine hot spots. Once the optimal temperature has been reached, the coolant water will be let into the radiator for energy dissipation. If the thermostat is not opening at this time, it may cause the lower radiator hose to stay cold, and at the same time, overheat the engine.
if coolant level in reservoir is over-full but radiator is empty
air pockets in the coolant may impair the water pump performance
clogged / corroded coolant system
Diagnosing coolant loss
this could just be from:
not having topped up the coolant for a long time
the engine has over-heated from prolonged excessive driving loads in hot weather
over-filling the coolant reservoir - it should be within the markers when cold
coolant in reservoir but not in radiator
consider faulty thermostat especially if the coolant loss only occurs on longer drives when engine is hot
thermostat usually opens at 70degC and this then allows the water to circulate and cool the engine
if the thermostat is stuck closed or not opening until a much higher temperature, the water pump will increase pressure with this pressure only being released by the pressure valve on the thermostat which allows some minimal water flow through it even if closed, and then via the reservoir cap which has a hole to allow release of pressure - hence the reservoir will be over-full in this scenario and steam will escape via the reservoir cap (and possible via the radiator cap)
possible water leak which stops the vacuum suction building up when coolant cools when engine off - this vacuum is needed to suck coolant from the reservoir via the top hose
check for signs of external coolant leakage
coolant leakage may be difficult to see directly as it may be a fine spray when under high pressure when engine is running
look for coolant stains with a torch
look for intact radiator hoses and connections
check the reservoir for leaks or a leaking cap
check the top of the radiator for evidence of fine cracks or leakage
check inside the car for evidence of coolant loss / dampness from the heater
check for signs of internal coolant leakage into engine and mixing with engine oil
check oil stick for white smearing of the oil on the stick
open oil cap and check for evidence in there - you will need a torch
internal engine leakage is a serious problem and needs to be rectified immediately to avoid serious engine damage - coolant anti-freeze is not good mixed with oil and will damage the engine
check for signs the coolant has entered engine piston area and being lost as steam in exhaust
steam coming from exhaust after engine has been running for a while
advanced options include combustion tests of coolant to ascertain if exhaust gases have made their way into the coolant
this could be from:
a small crack in the intake manifold gasket or the head gasket,
a defective/cracked Exhaust Gas Recirculation (EGR) valve (this uses coolant to cool down the exhaust gases before sending some back into the engine for better fuel economy
cracked head
cracked block (or cylinder liner)
a sealant additive to the coolant may fix this
pressure test the radiator
this requires a special air pump attached to radiator inlet and pumped to the pressure as indicated on the radiator cap
if no leaks found, consider pressure testing or replacing the radiator cap
still no cause found
faulty water pump
the car's water pump is the key to ensuring the engine runs properly
it is an impeller pump driven by the engine's drive belt, with the turning blades of the pump forcing coolant to flow through the engine and back to the radiator to be cooled by a forced air cooling fan
the wrong coolant will cause deposit-buildup inside the pump, which slows the ideal process of engine cooling.
the pump's impeller fin blades may corrode if either:
signs of leaking water pump from worn out gaskets and seals
coolant leakage at front centre of engine
rust or deposit build up around the pump
these can often be repaired before it gets worse
water pump making high pitched sound
catastrophic failure of the water pump is possible but unlikely and will cause a RAPID rise in engine temperature
faulty thermostat
checking to see if coolant needs replacing
the coolant should act to reduce corrosion and rust
use a multimeter set to DC voltage
while the engine is cold, take radiator cap off
start engine and run it at idle of 1500rpm to warm up
place negative probe of battery's negative terminal
place positive probe into the radiator coolant
if the meter reads 0.4V or less, the coolant is good; however, if it reads more than 0.4V, then the additives in the coolant that prevent electrolysis have broken down, which means the coolant should be replaced.
car heater not heating
this may be due to:
inadequate coolant
problems with the heater core
heater cores are typically situated directly in the back of dashboards
coolant may not be traveling through the heater core properly
the air from the blower motor is not reaching it
there’s a clog in the small tubing of the heater core
symptoms of this include:
clogged or broken heater controls
may need to replace some of the control buttons or your heater control valve.
The heater control valve is underneath your hood and acts as the switch that turns the heat on and off. If that piece is not working right, your car could get stuck blowing cool air into the cabin.
dysfunctional thermostats
If the thermostat gauge stays on the “C” even after the engine has time to heat up, you may have a broken thermostat. If the thermostat can’t signal to the car that the engine is warm, the coolant won’t be sent over to provide heat to your heater core and the air will stay cool. Thermostats are a relatively easy and inexpensive fix, so installing a new one can get your heater working again quickly.
water leaks
understanding a car cooling system
the car engine needs to be kept at an optimum operating temperature (usually around 100degC) which should not be too cold nor too hot and this is the prime role of the cooling system
coolant (either water or preferably an ethylene glycol based coolant which does not freeze in very cold conditions and will have a lower boiling point and less tendency to corrode than water) circulates the engine pushed by the water pump which runs continuously when the engine is running driven by a belt from the engine
the coolant is pushed to the top hoses of the radiator and then flows down through the radiator where the wind cools the coolant back down before it travels via the lower radiator hose to the thermostat and then back through the engine.
the thermostat is designed to prevent or substantially reduce water circulating when the engine is cold so that it attains optimum operating temperature faster
the thermostat has an internal sensing system on the engine side which at 70degC opens the spring-loaded valve
as a safeguard, the thermostat also has a small hole with a mechanical valve to reduce pressure build up if the thermostat fails to open
while the thermostat remains closed the lower hose from the radiator will be cooler than the top radiator hoses, once it opens, this difference reduces significantly
the radiator cap is a pressurised cap to intentionally build up pressure in the system as this increases the coolant's boiling point
the reservoir acts as two roles:
australia/car_overheating.txt · Last modified: 2022/04/27 19:28 by gary1