You already know warming up an old car is important; it only takes a few minutes, and you’ll avoid serious engine problems down the road.
So, how to warm up an old car? Start your car up without revving the engine; allow the engine to idle and warm for a few minutes before moving off. Use only light throttle application until the temperature gauge indicates normal.
Warming the engine and the transmission, especially in extremely cold conditions, is the kindest thing you can do. Cold fluids are hard to move, and stressing the engine without complete lubrication spells trouble.
In this post, you’ll learn how to warm up your classic car with the car, and you’ll also learn why it is so important.
If your classic car is from the mid-80s onwards, you’ll likely have fuel injection, which means you don’t have a manual choke lever. Modern cars use oxygen sensors in the exhaust system to measure the fuel-to-air ratio, and this helps the engine control module adjust the fuel ratio so the car warms up very quickly.
If your car is an earlier vintage, and you’re running a carburetor, you probably have a choke lever.
Some of the later carburetors had an auto choke fitted, but most didn’t. Anyway, to start an old carburetor car, you’ll need to pull the choke; this gives the engine some extra gas so it starts smoothly.
An internal combustion engine runs best when the air-to-fuel ratio is 14.7: 1, 14.7 parts air to one part gas.
When the old girl starts, it’s important not to rev the engine; this is when the damage is done. Just allow the engine to idle until the temperature needle moves off the bottom of the gauge.
It’s now safe to drive the car, but don’t accelerate hard until the engine temperature gauge reaches operating temperature, usually about 90° C.
Modern cars don’t need to be warmed up before driving but should be allowed idle for 15-20 seconds to build oil pressure before increasing the rpm, extending the time idling in extremely cold conditions.
I worked in a GM dealership in Canada; it regularly gets down to -50° in winter; regular problems included dead batteries, engine and transmission oil leaks, and power steering pressure hoses blowing off their fittings.
The solutions to these problems included using block heaters; people living in colder climates will already be familiar with block heaters.
It’s a heating element or patch that’s placed in or on the oil pan of the engine, depending on the design; it’s plugged into the household mains power supply when the car is not in use. This keeps the oil warm; it protects and speeds up the engine warm-up time.
Using lighter oil grades in the power steering systems prevented pressure hoses from blowing off.
The correct oil for your car is very important, especially in colder temperatures. If you live in a climate where the temperatures get well down into the minus, be sure your classic has the correct oil grade; even starting your classic in these extreme conditions can damage the engine.
Lighter synthetic oils last longer and, more importantly, flow faster in colder climates. Before winter, check the correct oil for your classic with your local parts store.
Winter grade oil flow:
- 0W xx -40°C
- 5W xx -35°C
- 10W xx -30°C
- 15W xx -25°C
- 20W xx -20°C
Why Is It Important To Warm Up A Classic Car?
It’s important for a few reasons, the most important of which is oil pressure. Oil, as you know, cools and protects the metal parts of your engine. Oil reduces friction between components; without oil and the oil pump that moves it, the engine would seize within a few minutes.
After you shut down your classic car, the oil coating the engine components immediately drains back to the oil pan.
Engine damage can happen when you restart your car, the metal components, while not completely dry, now only have a thin coat of oil, and they won’t get re-coated until engine oil pressure builds.
This takes a few seconds, so it’s very important that the engine isn’t unduly stressed during this period. Driving the car energetically before it’s up to temperature can cause oil leaks, and metal components, as you know, expand as they heat. While oil leaks are less serious, they are an irritant.
Cold weather brings other challenges, the oil pump may struggle to pump non-synthetic oil grades in minus conditions, and cold oil is thicker.
Turning the key and driving a classic car without warming up the engine and the oil runs a serious risk of causing excessive engine wear.
What Happens If You Don’t Warm Up A Classic Car?
Cars from the mid-’80s all had fuel injection, which means they were clever enough to have an automatic choke. Cars older than that were carburetors, and that means the operator had to adjust the fuel mixture by applying the choke.
If you don’t apply the choke, the car will be difficult to start and will buck and hop down the road, it’s known as kangarooing, and as a kid, it was a source of amusement.
If you don’t warm up an old engine before driving, you risk causing excessive engine wear. The oil pump may not have reached operating pressure, and that means the engine oil hasn’t traveled through the small engine galleries and coated the moving components.
It’s common for the top end of an engine to be damaged by cold engine acceleration; the camshaft is furthermost from the oil pump and is, therefore, last to get oil.
Metal changes shape as it heats, pistons, for example, may look round, but when they’re cold, they’re actually slightly egg-shaped. The shape can cause them to move about in the cylinder when cold and cause an abnormal noise known as a piston slap.
As the pistons reach operating temperature, they expand across the wrist pin and become round.
Often old engines will knock and make funny noises when cold but seem to disappear when warm. This can be attributed to engine wear and in many cases, just a character of the era of engineering.
Nevertheless, the noises are caused by excessive clearances, and revving an engine while cold can run the risk of spinning a bearing or worse.
How Can I Get My Car To Warm Up Faster?
This is a problem with lots of people that only commute a short distance; their car never really warms up; Brrrrr.
Have your coolant system serviced; back-flushing the coolant system removes years of crap blocking up the heater and radiator core. Replacing the water pump, fan belt (Aux), thermostat, and fresh coolant will have you on the right road.
A common cause of poor heat in older cars is an air-locked coolant system. Air-locking could simply be caused by an old or faulty rad cap, but bad hoses or clamps and a leaking heater core are common problem areas too.
The main components of a car cooling system include:
- Rad cap
- Water pump
- Water pump drive belt
- Fan switch
- Temp sensors
- Temperature gauge
- Heater core
A coolant system works by transferring the heat from the engine to the atmosphere. The radiator filled with coolant is positioned at the front of the vehicle; the air rushing at it as you drive down the road cools it.
The coolant is pumped through the engine which keeps the engine cool; it’s returned to the radiator once again to be cooled; this is a continuous cycle once the thermostat has opened.
The thermostat is a valve that blocks the passage of coolant to the engine until the engine reaches a certain temperature (about 195°F). Its purpose is to get the engine up to temperature quickly; a cold engine is inefficient and polluting; it also helps heat up the cabin heater quickly.
The thermostat is a mechanical component and is available in different heat ranges. Often referred to as winter thermostats (winter stat) or summer thermostats.
The Heater core is like a mini radiator, it receives heated coolant from the engine, and a blown motor blows air across the core to heat the interior of the car.
The fan, as you know, is designed to draw air at the radiator when the car is in traffic. It replaces the atmospheric air cooling the rad on the highway. The fan on modern cars is electric and is controlled by the engine onboard computer.
To get your car to warm up faster, consider changing your thermostat for a winter stat. Option two-place some cardboard down the front of the radiator; this prevents ambient air from cooling the coolant and causes the engine to heat more quickly, warmer engine equals a warmer cabin.
How long should I warm up a car? An older car should be idled without revving the engine for about ten minutes, and a modern car for about thirty seconds.
About the Author
John Cunningham is a Red Seal Qualified automotive technician with over twenty-five years of experience in the field. When he’s not writing about car repair, you’ll find him in his happy place – restoring classic cars.
- About the Author
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.