You'll be able to drive with a bad timing belt right up until you can't. What we mean by that is that your timing belt will continue to weaken and crack until it finally breaks. The moment your timing belt breaks your engine will shut down, often in a very catastrophically bad way.
How long can you drive on a worn timing belt?
It's hard to put a definitive number on just how long a timing belt is going to last. On average you can expect a timing belt to last 60,000 miles to 100,000 miles.
What happens if you drive with a broken timing belt?
If a timing belt breaks while driving in an interference engine, the camshaft stops turning leaving some of the engine valves in the open position. This may result in a heavy damage to the engine with broken or bent valves, damaged pistons and, possibly, destroyed cylinder head and block.
How does a car act when the timing belt is bad?
Your Car's Engine Won't Turn Over
When your car's timing belt is broken or irreplaceable, your engine will not be able to ignite or turn over properly. Oftentimes, the timing belt will break while the car is in motion. This can cause serious damage to cylinder head hardware like rocker arms, push rods, or valves.
Related Question Can I drive with a bad timing belt?
How do you tell if timing belt needs changing?
If it is becoming worn, the belt will appear to look glazed or glossy on the underside. This means the rubber is getting hard and will not provide the flexibility the belt needs. Some signs are much more obvious, such as cracking or fraying. Belts with that kind of damage should be replaced immediately.
Will a new timing belt improve performance?
No timing belt will give an increase in performance - it's just not possible. Its main job is to keep the timing in check. Having your timing belt replaced and noticing an increase in performance is just a mix of the engine operating at peak efficiency and a good hit of placebo effect thrown in for good measure!