Engine whine/hum diagnosis help (1 Viewer)

[dgamby]

Morning!

So this week my 05 LX470 started making this fun whine/hum on startup. It is directly tied to rpms. goes up and down with the engine, follows the rpms at shift points etc... It doesn't seem to go away when the engine warms up. I didn't drive it but left it running in my driveway about 20 minutes this morning and the sound was still there. She has just over 200k on the odometer. Timing belt, water pump, crank seal, drive belt and drive belt tensioner were done before I purchased but at a Lexus dealer at 182k miles about 3 years ago. I just had an axle seal fixed and a bunch of fluids baselined at my shop but have had it back for about a month so I don't think that would be related. Anybody have any insights about likely culprits? Thanks for the help!

 

[2001LC]

Short video & sound bit, makes remote diagnostics even more difficult. It tried to see if a fan bracket wobble. You moved to fast past it.

Turn AC on then off, see if difference.
With AC off. Use a stethoscope on drive belt pulleys (on front bolt), fan bracket (on body behind pulley/belt), vane pump and alternator (on their case/body).
Remove belt run engine no more than 2 minutes. See if still present.

Note: Vane pump (AKA power steering pump) uses ATF not power steering fluid (see cap). They don't like anything else or to be run dry or clogged screen. The sound is very much like I hear from Vane, with wrong fluid, clogged screen on cold morning.

Alternator before going bad, often sound similar.

Come back and let us know results.

 

[2001LC]

 

[dgamby]

Short video & sound bit, makes remote diagnostics even more difficult. It tried to see if a fan bracket wobble. You moved to fast past it.

Turn AC on then off, see if difference.
With AC off. Use a stethoscope on drive belt pulleys (on front bolt), fan bracket (on body behind pulley/belt), vane pump and alternator (on their case/body).
Remove belt run engine no more than 2 minutes. See if still present.

Note: Vane pump (AKA power steering pump) uses ATF not power steering fluid (see cap). They don't like anything else or to be run dry or clogged screen. The sound is very much like I hear from Vane, with wrong fluid, clogged screen on cold morning.

Alternator before going bad, often sound similar.

Come back and let us know results.

AC on off makes no difference with the exception that the noise follows the rpms moving slightly when the AC kicks on.

Power steering fluid reservoir is appropriately full. I'd be surprised if wrong fluid was used since most of her life she was taken to Lexus, but stranger things have happened. Didn't dig in to see if screen was clogged yet.

I'll have to pick up a stethoscope to test that. And find a block of time without kids running around if I want to pull off the belt. With stethoscope am I just listening to see if I can isolate that whine to one of those parts?

Would a battery test at advance auto pick up an alternator that was starting to go?

Once again, appreciate the deep depths of wisdom being shared here.

 

[Les Summer]

I was dealing with a whine I forever thought was coming from my transmission. It was synonymous with when I was at idle or coming to a stop after driving for a long period. I even believed it was my transfer case for a while. Low and behold, months later, my alternator died on me, and after I changed out the alternator, the whine disappeared forever. I'm so glad the whine is gone. It was the OG alternator with around 285K on it.

 

[dgamby]

I stand corrected. I took a drive across town and the whine disappeared once the car was warmed up. Does that point in any particular direction?

 

[94SRUNNER]

I’d be interested to hear if it happens again tomorrow if you take it on another drive.

Alternator is a possibility. Might be worth having a shop or auto parts store test the alternator starter, and battery.

 

[dgamby]

So a way to late update on this. The sound completely stopped for several months. So I couldn't pin point where it was coming from. Came back for a few days and went away again. Then I started getting the battery discharge light. Checked the alternator at a local parts store and it came back as good because it wasn't acting up at that instance. After that the alternator quickly started truly dying and I could see the batter draining as I drove and got all kinds of nice warning sounds and lights. New alternator got it all sorted out.

 

[2001LC]

There is a bracket on alternator, that wire hangs on. This bracket needs moving over to new alt.

 

[dgamby]

There is a bracket on alternator, that wire hangs on. This bracket needs moving over to new alt.

This is one I didn't attempt. Didn't have the time and read some other folks on here not overly enjoying this repair. Had a local indy toyota/lexus shop do it. I'm assuming the bracket got moved over...

 

[2001LC]

This is one I didn't attempt. Didn't have the time and read some other folks on here not overly enjoying this repair. Had a local indy toyota/lexus shop do it. I'm assuming the bracket got moved over...

Make sure. If not there, call and have them pull from old.

 

[dgamby]

Make sure. If not call and have the pull from old.

Will it be easy to see from underneath? What am I looking for?

 

[2001LC]

Yes for me, relatively easy:
From underneath with #1 skid/cover off. Use camera w/flash. Shoot pic from front to rear between ALT and body/frame/fender well.
From engine bay. Shoot from where you can reach down between shock/frame and engine forward of engine mount. Shoot pic toward front at back of ALT
From fender well, peeking behind splash shield.

Bracket circled in yellow.

View from front looking back.
Bracket and its bolt missing
Wire housing has clip for bracket, but nowhere to attach. Bracket Bolt capture threads on alternator empty.

Boot, not properly tucked in

Above pic we see the protective cap is on hot lead.