Turbochargers used to be found mainly on performance cars. Today they are common on everyday sedans, SUVs and pickups, because they let a smaller engine make the power of a larger one. Knowing how a turbocharger works, and recognizing the warning signs of turbo trouble early, can help you avoid a costly failure.
If your turbocharged vehicle is down on power or has a warning light on, an engine diagnostic check is the place to start, because many turbo symptoms are actually caused by simpler parts around it.
How a turbocharger works
An engine makes power by burning a mix of air and fuel. The more air it can pull in, the more fuel it can burn and the more power it can make. A turbocharger forces extra air into the engine using energy that would otherwise go out the tailpipe.
A turbo has two wheels on a shared shaft. On the exhaust side, hot gases leaving the engine spin the turbine wheel. On the intake side, the compressor wheel spins with it, drawing in fresh air and pressurizing it. That pressurized air is called boost.
Compressing air heats it, and hot air is less dense, so most turbo engines route it through an intercooler before it reaches the intake. A wastegate lets some exhaust bypass the turbine to keep boost from climbing too high, and many engines also have a valve that releases excess pressure when you lift off the throttle.
The turbo’s shaft spins extremely fast and runs very hot. It rides on bearings fed by engine oil, and many turbos are also cooled by engine coolant. That dependence on oil is the single most important thing to understand about turbo care.
Signs of turbo trouble
- Loss of power. The car feels sluggish, especially when merging or climbing, and may not pull the way it used to.
- Unusual noise. A rising whine or siren sound that is louder than before can mean bearing wear. A hiss or whoosh under load can mean a boost leak.
- Blue or gray exhaust smoke. Worn turbo seals can let oil into the intake or exhaust, where it burns.
- Using more oil. If you are adding oil between changes, the turbo is one of several possible causes.
- Check engine light. Codes for underboost, overboost or wastegate faults point toward the boost system, though not necessarily the turbo itself.
- Reduced-power mode. Some vehicles limit engine output when they detect a boost problem to protect the engine.
Smoke color can be a helpful clue; our guide to why smoke is coming from your car explains what different colors usually mean.
It is not always the turbo
Turbos are expensive, so it pays to confirm the diagnosis before replacing one. Many boost problems come from cracked or loose intake hoses, a leaking intercooler, a faulty boost pressure sensor, a sticking wastegate actuator, a vacuum leak, or a clogged air filter. A technician can check for leaks, read live boost data and compare it to what the engine is asking for.
When a turbo does fail, the root cause is often oil-related: oil that was overdue for a change, the wrong oil, low oil level or a restricted oil feed line. If that cause is not addressed, a new turbo can fail the same way.
Habits that help a turbo last
- Change the oil on schedule with the viscosity and specification in your owner’s manual. Our oil change service uses oil that matches your engine’s requirements.
- Keep an eye on the oil level between changes, since turbo engines can be sensitive to running low.
- Warm up gently. Avoid hard acceleration until the engine has reached normal operating temperature.
- Cool down after hard work. After pulling a load or climbing a long grade, drive easy for the last stretch before shutting down.
- Replace the air filter when needed. Debris that gets past a damaged filter can chip the compressor wheel.
- Deal with leaks and warning lights promptly instead of letting the turbo work harder to make up for them.
For a broader look at the engine the turbo is bolted to, see our guide to the main parts of a car engine.
Have your turbo engine checked in Hermitage
If your turbocharged car has lost power, started making new sounds or is using oil, Music City Auto Repair can test the boost system, find the cause and give you an estimate before any work starts. Request an appointment online or call 615-600-5994.
Frequently asked questions
Do I need to let a turbocharged engine idle before turning it off?
After normal driving, most modern turbo engines can be shut off right away. After hard driving, such as climbing long grades or pulling a trailer, driving gently for the last stretch or idling briefly lets the turbo cool a little while oil keeps flowing. Check your owner's manual for any specific guidance.
What does a whistling sound under the hood of a turbo car mean?
Turbos make a soft whistle normally, but a new or louder hiss or whistle, especially with reduced power, often points to a boost leak from a loose clamp, cracked hose or damaged intercooler pipe. A worn turbo can also produce a siren-like whine. Either should be inspected.
Do turbocharged engines need a special type of motor oil?
Many turbocharged engines call for a specific oil viscosity and a particular manufacturer or industry specification, often a full synthetic. The turbo's bearings run hot and fast, so using the oil listed in your owner's manual and changing it on time matters more than usual.
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