Bad Timing Belt Symptoms and What Happens If It Breaks

Bad timing belt symptoms are rough running, a stall, an engine that cranks but won't start, and a noise from the pulleys the belt runs on. First check that your engine has a timing belt at all, because many run a metal timing chain instead, which lasts far longer but can stretch and rattle.

What are bad timing belt symptoms?

Most bad timing belt symptoms show up once the belt has slipped or broken: rough running, a stall, or an engine that cranks without starting. The one that can come earlier is a noise from the parts the belt runs on.

Here are the five signs of a bad timing belt, the last one for wet-belt engines only:

1. A noise from behind the timing cover

You'll hear a whine, a chirp or a slapping sound from the front of the engine, changing with engine speed. It points to the parts the belt runs on, a tensioner or an idler pulley, which keep the belt tight and on its path. It can also be the belt rubbing where it shouldn't.

Tell the shop when it happens, cold or warm, and whether it rises with the revs. The section on what a bad timing belt sounds like sorts the sounds out.

2. Oil or coolant on the front of the engine

You'll see oil or coolant around the timing cover, or drips under the front of the engine. That points to a leaking camshaft or crankshaft seal, or to a water pump the belt drives, and oil softens the belt's rubber over time.

A leak isn't a worn belt, but it shortens the belt's life, so ask for it to be fixed in the same job when the belt is close to due. Our guide to bad water pump symptoms shows what a pump leak looks like.

3. Rough running and a check engine light

You'll feel the engine shake or stumble, lose power, and the check engine light comes on. That points to a belt that has slipped a tooth, so the valves open and close at the wrong moments.

Honda's dealer instructions for its timing belt recall say a slipped belt sets camshaft timing codes, such as P0341, and makes the engine run rough. Those codes have other causes too, so ask whether the timing has slipped before anyone replaces a sensor.

4. An engine that cranks but won't start

The engine spins, often faster than usual, but never catches, or it died on the road and won't restart. That points to a broken or shredded belt, and the normal-sounding starter is what makes it confusing.

A starter that doesn't turn at all points to the battery or the starter instead. Our guide to a car that won't start covers those causes once the belt is ruled out.

5. An oil pressure light, on a wet-belt engine

You'll see the low oil pressure light, sometimes just before the engine loses power, and on any engine that light means stop. On a wet belt engine, whose belt runs inside the oil, pieces of a worn belt can clog the oil pump's pickup screen.

NHTSA, the federal vehicle safety agency, is investigating this on Ford's 1.0-liter EcoBoost, and many of those failures came well before the belt was due. A separate oil pump belt on some automatic Focus and EcoSport models can fail the same way, as our Ford 1.0 EcoBoost wet belt guide explains.

Oil on the front of the engine

Can you drive with a bad timing belt?

Not once it has stalled or won't start, and not far if it runs rough with the check engine light on. A noise from the belt area means have it checked soon, as the noise section below explains.

If the engine stalls or cranks without starting, don't keep cranking it: have it towed. On a wet-belt engine, treat the oil pressure light the same way and stop the engine.

A belt that's past its interval with no symptoms can still drive normally, but it can snap without notice. On an interference engine, the pistons can then hit the open valves and ruin the engine, so book the job soon.

Is there any warning before a timing belt breaks?

Often there's none: timing belt warning signs are rare. A belt in good shape is close to silent, and a worn one is often just as quiet.

Plenty of belts fail without a sign, and NHTSA's wet-belt investigation records failures that came with no warning at all. That's why carmakers set the belt by the calendar and the odometer rather than by a symptom.

When there is a warning, it tends to come from the parts beside the belt, not the rubber. Either way, treat a belt past its interval as due, even when the car sounds and drives fine.

What does a bad timing belt sound like?

A bad timing belt can sound like nothing at all, because most timing belt noise comes from the parts around it. These are the sounds people blame on the timing belt, and what each one tends to be:

• A whine or rumble that rises with engine speed. A tensioner or idler pulley bearing drying out. That's the part that can seize and shred a good belt.
• A chirp from the belt area once the engine is warm. On some Honda V6s, the belt touching the edge of the crankshaft pulley. Honda fixes it with a shim, not a new belt.
• A slap or flutter at idle. Can be a loose belt or a weak tensioner letting it whip against the cover.
• A squeal at start-up or when you turn the wheel. That tends to be the accessory belt outside the cover, the one that drives the alternator.
• A tick that speeds up with the revs. Sometimes a loose belt, but low oil or the valves can tick the same way, so check the oil level first.
• A rattle for a few seconds after a cold start. A timing chain, not a belt, so check which one your engine has.

Sound alone can't pinpoint the part, so ask the shop to find which pulley it comes from before it quotes a job. Our guides to an engine ticking noise and a whining noise when accelerating cover the look-alikes.

Some owners who describe a timing belt actually have a chain, which is metal and runs in oil. It tends to last far longer than a belt but can stretch and rattle, and our guide to belt or chain shows which one you have.

The tensioner and the idler

What happens if a timing belt breaks while driving?

The engine stops at once, and it won't restart. The brake pedal goes heavy, and on many cars so does the steering, because their assist needs a running engine.

Both still work if you push harder, so steer and brake firmly. If it happens on the road, do these in order to get the car stopped safely:

• Turn on the hazard lights. Drivers behind you need to know you're slowing down.
• Steer firmly to the shoulder. The wheel may need far more effort than usual.
• Don't turn the key off while rolling. Honda's 2016 Civic manual warns that pulling the key out while driving locks the steering.
• Brake with steady, firm pressure. Don't pump the pedal, because each press uses up the little assist that's left.
• Leave the engine off and call for a tow. Cranking it again can add damage inside, and it won't start anyway.

Will a broken timing belt ruin the engine?

On an interference engine, often yes, because the valves and pistons take turns in the same space. When the belt stops, valves left open stay open, and the pistons hit them.

That bends valves and can damage the pistons, so the repair means taking the cylinder head off rather than a belt job. Honda's recall instructions call for a leak-down test, which checks each cylinder and shows whether the engine was damaged, before any engine parts are ordered.

On a non-interference engine, a broken belt tends to mean a tow and a new belt. Your manual or a dealer can tell you which you have, and until you know, it's safer to assume interference.

How do you know when a timing belt needs replacing?

Your maintenance schedule tells you, in miles and in years, and whichever comes first decides. The limit belongs to your engine, not the model.

1. Find your engine's interval in the owner's manual or maintenance schedule. Note both numbers. Some cars, such as Honda's, show a maintenance code on the dash instead. Some books give a shorter interval for extreme heat, cold or towing, so use that one if it fits how you drive.
2. Check the records. Look for a receipt that names the timing belt. If there's none and the car is past the interval, assume it was never done.
3. Work out which limit you hit first. Our timing belt due calculator does this, and on a low-mileage car the years can run out first.
4. Ask for a look if it's close. Some covers have a small inspection plug, and the next section says what a shop looks for.

The belt line in the book

What does a worn timing belt look like?

Cracks, a shiny glazed back, missing teeth or, on a dry belt, oil on it mean replace it now. A shop can see them through the small inspection plug some covers have. A belt that looks fine can still be worn out inside. The interval wins over a good-looking belt.

A worn timing belt

What should you ask the shop?

Ask what the quote includes and whether the timing was checked before any part is named. Our timing belt replacement cost guide covers what the job includes and what changes the bill.

Before you pay, run your VIN, the 17-character number on the windshield, through our free VIN checker. It lists your model year's recalls, and a dealer can check the free timing belt fixes.

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Common questions

Asked most often

Do you replace the water pump with the timing belt?

Not always. Honda's 2016 Pilot schedule replaces the belt and only inspects the water pump, so ask whether yours needs one.

Does a bad timing belt cause a check engine light?

It can. A belt that has slipped a tooth puts the camshaft out of step, which sets a camshaft timing code and makes the engine run rough.

How do I know if my timing belt is going bad?

Mostly from the calendar and the odometer, because many belts give no sign. Once it's past the interval in your engine's book, treat it as due, and a whine from the front or rough running makes it urgent.

This article is general information, not advice about your specific vehicle. See the disclaimer.