You’re sitting in traffic or just driving along innocently and suddenly you hear something come from your car that you have never heard before. From clicks and ticks to knocks and pings, all cars make noises at some point or another. You’ll learn very quickly the nuances of your car, but once in a while a noise comes along that gives you pause.

A good rule of thumb is to take your European car to the mechanic for a repair as soon as you hear something off or different so the problem can be addressed before it gets worse. Strange engine noises can raise a red flag for anything from a simple fix to a complete engine overhaul. Having a high-end European vehicle means you can’t take any chances with its operation. Here are five engine noises that require immediate attention.

1. Squealing While Breaking

Squealing that’s triggered when you are braking could mean numerous things, not all of which are dire. It could just involve dirt build-up on your brake rotors, pads, drums or shoes. A good cleaning will take care of this. However, a more serious cause could be worn brake pads or shoes, or brake calipers that have been improperly mounted or have come loose. Worn brakes will fail at some point, so get your brakes looked at immediately.

2. Engine Hissing

A hissing engine can signal an overheating engine or a plugged exhaust system/catalytic converter. It could also mean that the vacuum has leaked. Whatever the case, make an appointment for repair immediately, as a blown engine poses a major safety risk, not to mention it can cost you thousands in repair costs.

3. Grinding Transmission

The sound you hear will depend on the make of the car. Manual transmissions may grind when you engage the clutch and shift. Automatic transmissions will produce a jerking and shaking when shifting occurs as opposed to a grinding noise. No matter the kind of sound or sensation you encounter, take your vehicle to a trusted mechanic. You may need an adjustment on your shift linkage or clutch.

4. Popping Exhaust

A popping noise can indicate your vehicle has a serious problem that requires immediate attention. A common cause is leaks, especially within the fuel injector. However, these kinds of sounds may also originate from holes in the muffler. Treat all exhaust leaks seriously. Otherwise, you will be prone to engine damage, a boost in fuel consumption and poor emissions ratings.

5. Knocking or Pinging

If you notice a knocking or pinging noise, it may be due to an ignition problem, often occurring when fuel ignites inside the cylinder. Ignition can result in a bad fuel filter, fuel injector, bad distributor cap and damaged spark plug. Before taking on a DIY repair, you should always take your vehicle to the mechanic for a tune-up and some troubleshooting to identify the problem quickly.