* Valve train issues: This is the most likely culprit for a clicking sound that increases with RPM. It could be:
* Worn rocker arms or lifters: These components regulate valve movement. Wear causes clicking as they lose their precise contact.
* Low oil pressure: Insufficient lubrication leads to increased wear and clicking in the valve train. A blown head gasket can *cause* low oil pressure, but the clicking is a direct result of the insufficient lubrication.
* Sticky or failing hydraulic lifters: These components automatically adjust valve clearance. If they're sticking or failing, they can produce a distinct clicking sound.
* Connecting rod issues: While less likely to speed up directly with RPM, a severely worn or damaged connecting rod can make clicking noises. However, this would usually be accompanied by other serious symptoms.
* Loose components: Something may have come loose inside the engine, such as a bolt or other small part. This is less common but possible.
Why a blown head gasket isn't the primary clicking noise source:
A blown head gasket typically leads to symptoms like:
* Loss of coolant: Coolant leaks into the engine oil or exhaust.
* White smoke from the exhaust: Indicates coolant burning in the combustion chambers.
* Compression loss: Leads to reduced engine power and possibly misfires.
* Overheating: The engine may overheat due to coolant loss.
* Oil contamination (emulsified oil): Oil and coolant mix, creating a milky substance.
The clicking noise is a separate mechanical issue and is likely related to the internal engine components responsible for moving parts (valves, lifters, etc.). The head gasket failure might worsen the problem (e.g., by reducing oil pressure) or mask other sounds, but it's not the direct source of the clicking.
What you should do:
1. Don't drive the car: Continued driving with a blown head gasket and potentially damaged internal components could cause catastrophic engine failure.
2. Get a professional diagnosis: A mechanic can pinpoint the source of the clicking noise and assess the extent of the head gasket damage. This requires a proper inspection, likely including a compression test and possibly oil analysis.
Ignoring the problem will likely lead to more extensive (and expensive) repairs. A prompt diagnosis is crucial.
