* Rod Knock: This is a very serious issue. A connecting rod bearing is worn or damaged, allowing the rod to strike the crankshaft. This is usually accompanied by a rhythmic knocking that increases with engine speed. This often requires a rebuild or engine replacement.
* Main Bearing Knock: Similar to rod knock, but involves the bearings supporting the crankshaft itself. Again, a serious problem requiring major repair.
* Wrist Pin Knock: The wrist pin connects the piston to the connecting rod. If worn or damaged, it can cause a knocking sound.
* Piston Slap: This is a less severe (but still concerning) issue where the piston is slightly loose in the cylinder bore. It's often a tapping or knocking sound, usually more noticeable when the engine is cold.
* Cam Bearing Wear: Worn camshaft bearings can cause a knocking or ticking noise.
* Valvetrain Issues: While less likely to cause a loud *knock*, worn or damaged lifters, rocker arms, or pushrods can contribute to unusual noises. This is more of a tapping or clicking than a deep knock.
What to do immediately:
1. Stop driving the vehicle. Continuing to drive with a knocking engine will almost certainly lead to irreparable damage.
2. Have the engine inspected by a qualified mechanic. They can diagnose the precise cause of the knock using diagnostic tools and a visual inspection.
3. Do not add any engine additives. These are unlikely to fix a serious mechanical issue and might even mask symptoms, making diagnosis more difficult.
Possible causes that are less likely but should be considered:
* Loose or damaged components: Although less probable given the escalating noise, something could be loose and rattling around.
* Exhaust system issues: While typically a rattling or rumbling, a severely damaged exhaust component *could* create a sound that sounds like a knock.
The progressive worsening of the noise strongly suggests significant internal engine damage. Get a professional opinion as soon as possible. The cost of repair could be substantial, potentially exceeding the value of the vehicle depending on the severity of the damage.
