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Hi All-
LOVE ETCG .. been watching and learning and enjoying for years. I’m up against a strange one here for sure.
It’s a 2012 Lincoln Navigator with about 220k miles on it. Recently it has developed the strangest noise coming from the engine compartment. It sounds like a distant siren and the sound is clearly associated with engine RPM. The noise generally starts around 900 / 1000 RPM and will continue through about 2,000 RPM and it goes away above 2k rpm. What makes the sound so bizarre is that it sounds like the sound is “changing gears.” Oh .. by the way, this is with the vehicle stationary (in park or neutral). As you slowly accelerate from 1k -2k RPM, the pitch of the sound will start low and increase to a point, then it will “change gears” and the pitch will return to the lower end and slowly rise again. It will go through this cycle multiple times while slowly and steadily increasing RPM from 900 – 1k RPM.
There are no maintenance light of CEL’s on. There are no unusual indicators, gauges all look normal, driveability is excellent and there are no other indications that there is something awry.
The only thing I’ve noticed recently is that my coolant levels were a little low. I’ve topped it off, but so far the noise persists.
Here is a video doing my best to capture the sound. It’s hard to tell because there is so much engine / fan noise but the engine RPM is slowly increasing from idle – 2k rpm
Any ideas?
Chris
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Replies
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Inspect your drive belts, tensions and pulleys.
If needed remove one belt at a time and see if the sound stops.
Check all tensioner bearings for any gritty or grinding same for any accessoriesThanks nightflyr. When I get home tonight or sometime tomorrow I’ll see what belt(s) I can remove. Elsewhere someone suggested removing the serpentine belt and starting it up briefly to see if the sound persists. I honestly don’t remember seeing any other belts, so I guess I’ll only be able to determine if it’s something driven by the serpentine or not.
The unusual shifting nature of the sound is what really has me baffled. I sure wish someone could explain that to me.
The unusual shifting nature of the sound is what really has me baffled. I sure wish someone could explain that to me.
That is fairly easy..
If it is a belt or drive accessory, it will shift speed along with engine rpm.
When your driving the engine rpm will change (lower) when going into higher gears.
It can sometimes disappear above a certain speed.Yes go ahead and do that. I’ve also seen alternators do that at times when the bearings wear out. It could very well be that your alternator bearing is worn out and in that case you would just get a new alternator. The way you would check that is remove the serpentine belt and then spin the bearing on the alternator. It shouldn’t make any noise at all, if you hear noise then it’s toast.
[quote=”nightflyr” post=204401]The unusual shifting nature of the sound is what really has me baffled. I sure wish someone could explain that to me.
That is fairly easy..
If it is a belt or drive accessory, it will shift speed along with engine rpm.
When your driving the engine rpm will change (lower) when going into higher gears.
It can sometimes disappear above a certain speed.[/quote]I would understand and agree with this except that while the engine RPM is “linear” so to speak .. meaning that I steadily increase from idle to 2k RPM in a straight, smooth steady line, where as the sound “sifts gears” during this time. Meaning that the tone or pitch of the sound will increase to say .. 900 RPM, and then the sound will reset back to the low pitch and then climb back up to the high pitch at 11oo RPM, and then it will “shift” again and then begin climbing again to 1300 RPM and it cycles again. So while the engine RPM climbs slow and steach straight through from idle to 2k RPM, the mystery sound cycles through this low to high pitch several times throughout the RPM climb from idle to 2k RPM.
[quote=”musiccity365″ post=204403]Yes go ahead and do that. I’ve also seen alternators do that at times when the bearings wear out. It could very well be that your alternator bearing is worn out and in that case you would just get a new alternator. The way you would check that is remove the serpentine belt and then spin the bearing on the alternator. It shouldn’t make any noise at all, if you hear noise then it’s toast.[/quote]
While I can’t logically explain why this sound would change (see my quoted response above), several people have suggested the alternator .. and so I suppose that where I’m leaning at the moment. I just can’t get my head wrapped around why the sound “shifts” gears, while the RPM steadily increases. IE. the mystery sound cycles through 2 maybe three “gear shifts” while the RPM is a steady slow increase from idle to 2,000 RPM.
Nonetheless .. since this is my only real lead at the moment, I’ll eliminate it as a possibility and see what happens.
[quote=”relative4″ post=204420]Is it an EcoBoost? Sounds like a bad turbocharger.[/quote]
It’s not an Eco Boost that I know of .. but that definitely crossed my mind as well .. that the sound could be a turbo fan of some sort. I’ve only owned one car that was turbo charged that I know of (Saab 93) and even when it was performing properly, it was pretty unmistakable (additionally it had indicators on the dash). This vehicle doesn’t have any of that. I’m pretty sure this engine is just the standard flex fuel 5.4l V8
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