You may be surprÂ­ised to discover that a carbon monoxide (CO) detector really isn't a complicated piece of equipment. Housed inside a plastic chamber approximately 3 inches (7.6 centimeters) in diameter are parts that work in unison to alert a househoÂ­ld when lethal gas is detected.
This type of noise is usually caused by malfunctioning valve lifters or an exhaust manifold leak. If the noise lasts for more than a minute and completely disappears or dimishes after the engine is warm, the most likely cause is an exhaust manifold leak.
Aluminum hydroxide gel in tank or plumbing is one of the main causes of the rumbling noise in the heaters, while the mineral buildup can also be a factor. The aluminum hydroxide gel is the result of the chemical reaction between the anode rod and water condition.