Anybody have any idea about a ticking sound from engine compartment. Here are the clues:
* Have observed this since at least probably 2009.
* Affects a 2000 Saturn LW1 with DOHC 4-cylinder engine
* It’s a mechanical “ticking” sound that seems to come from the right side under the hood
* It only happens in cold weather
* It typically starts a couple of minutes after the car is first started up on a cold morning
* It typically goes away when the engine warms up (after several minutes)
* It always repeats at the same rate, maybe about 7?8 ticks per second
* It is independent of engine RPM
* It is independent of vehicle speed
* Sometimes (but not always) it stops when you lift your foot off the accelerator (it may tend to do this after the engine has warmed up a bit). When you depress the accelerator it resumes
It doesn’t seem to affect performance but I’d love to know what it is and whether I need to worry.
You say it “seems” to come from the right side under the hood, but I have to say that given what you’ve provided it isn’t clear whether or not you’ve actually opened up the hood while the noise is there to look around.
So if you haven’t actually done this, do it and see if you can get a bit more info on the approximate location of the noise. A piece of tubing or small hose works pretty well as a makeshift stethoscope for zeroing in on noises - but be careful of moving parts.
Sometimes a ticking sound like that is from an exhaust leak through a cracked exhaust manifold or leaking exhaust manifold gasket. And it could be induced when low temps cause the crack to expand, and disappear when the engine warms up and the manifold expands, closing the crack. That’s a bit of a stretch, but the only thing I can think of.
Noise from an exhaust leak would, however, be dependent on RPM. It’s difficult to imagine any engine noise that would NOT be RPM dependent.
I’d also take a look at the timing chain and tensioner.
Could be a vacuum leak causing the heater door to open and close.