Question: My temperature warning light is on. Is it okay
to drive the car?
Answer: Not unless you want to risk damaging your engine.
When the temperature light comes on, it means your engine is
overheating. An engine should not overheat if the cooling system
is properly filled and is working normally -- even during hot
weather or stop-and-go driving. Sometimes abnormal driving conditions
such as towing a heavy trailer during hot weather may overload
the cooling system's capacity to control heat, but usually a temperature
warning light means trouble.
WHAT TO DO:
Stop driving immediately, pull over to the side of the road, shut
the engine off and wait for things to cool down.
WARNING: Do not attempt to open the radiator! The radiator contains
hot water under high pressure. Opening the cap could allow steam
and water to blow out and burn you. There's nothing to be accomplished
by opening the cap while the engine is still hot, so let your
vehicle sit and cool off.
After things have cooled down (wait at least half an hour or more),
then you can open the radiator cap and check the coolant level
if you think it might be low. Place a rag over the cap first,
and slowly turn the cap until it stops at the first detent. This
should allow residual pressure to be released. Wait until all
pressure has been released before removing the cap the rest of
the way.
Add water to the radiator if it is low. Actually, you should
add a 50/50 mixture of antifreeze and water to maintain the proper
freezing, boilover and corrosion protection. But in most cases
when this happens, it's an emergency situation and you don't have
a jug of antifreeze handy. If that's the case, you'll have to
add antifreeze later.
Visually inspect the system for leaks. Common leak points include
radiator and heater hoses, the water pump and the radiator. Internal
leaks (such as a crack in the head or engine) can't be seen and
can only be diagnosed by pressure testing the cooling system.
See related question #14 for other causes of overheating.
IF YOU DON'T STOP DRIVING...
If you keep driving an engine that is overheating, it can cause
serious damage. The engine may start to knock (caused by detonation),
which in turn can cause piston, ring and head gasket damage.
As the internal parts of the engine expand from the excessive
heat, clearances may be reduced to the point where metal-to-metal
contact occurs. Valve stems may gall and stick, and the pistons
and camshaft might scuff or seize.
Severe overheating also creates tremendous thermal stress in the
head(s) and block. This, in turn, may lead to cracking and/or
warpage. This is a common problem with overhead cam engines that
have aluminum heads.
The only vehicle that can be "safely" driven when the
temperature warning light is on a late model Cadillac with a Northstar
V8 engine. Cadillac engineers designed the engine control system
to automatically deactivate half of the engine's cylinders if
it senses an overheating problem. This reduces the heat (and
power) being generated by the engine, and it allows the "dead"
cylinders to pump air through the engine for internal cooling.
The system is designed to provide a "limp-in" mode
so the vehicle can be driven to the nearest service facility or
Cadillac dealer for repairs. It is not designed for continuous
driving.
