I’m trying to diagnose a sound that I’ve been having the last 6 months from the engine bay. Sounds like a moose far off in the distance. It’s a groaning/howling sound that is deep and medium to high pitched which slowly rises in pitch, then suddenly shoots down in pitch (like someone has shifted to the next gear) and then slowly rises higher in pitch , and keeps repeating this pattern for 10 seconds to 1 minute until it finally just fades away. It ONLY happens after first starting engine stone cold in the morning. And it seems to happen more on cold mornings.
I assumed it was belts or pump bearings, but I’ve recently ruled those out. The sound is influenced if I give it some RPMs, but it is indirectly related. Meaning, there’s a bit of a delay to the sound giving it rpms. If anything, the sound just gets louder, not different in pitch.
I thought it may be brake accumulator vacuum, but pressing brake pedal (to relieve pressure?) makes no difference.
The sound will also vibrate the chassis a wee bit. It is very hard to determine where the sound is coming from. It’s just the general engine vicinity, more on the left (drivers) side.
Reading archives, all I can think of is power steering pressure building up in the hoses/rack? What does this mean? BUT if i turn the steering wheel back and forth, it makes no difference to the sound.
I can’t think of anything else, except maybe coolant flow?
The sound does remind me of water pipes in a house making a howling sound, like from a home heating radiator.