Help me diagnose this whine between 1800-2000 rpm

SFHLibertyCRD · **Posted:** Fri Nov 14, 2014 2:58 pm

Hi all. I'm getting a new sound that I can only describe as an "electrical" whine (does not sound mechanical or like turbo). It occurs when driving under normal load and accelerating between 1800-2000rpm until it shifts into next gear or I let off accelerator. It is very subtle and not easy to hear, but I made a few annotated videos. The second video is probably the clearer of the two:

https://www.youtube.com/watch?v=tYl0KJvu184
https://www.youtube.com/watch?v=XUsCWy5nNpw

Is there anything that kicks in at that engine speed or before the tranny shifts that would make a noise like this? Any ideas what this is?

Back story: I recently changed my crankshaft position sensor. Long story short, in the process I ended up removing the wrong heat shield next to the turbo looking for the cps which involved removing a whole bunch of other parts including: airbox to turbo hose, top samco hose, coolant temp sensor, plugs for coolant, maf, and a few others on the same harness section. It also involved a little spilled coolant from the temp sensor hole (which I hope didn't hit any electrical components). I also cleaned all contacts with a blast of contact cleaner before putting back together.

I also realized that my transmission fluid was run low by the previous owner. It took about 2 quarts to top it off. But I noticed the whine before I topped it off so I don't think that is relevant.

SFHLibertyCRD · **Posted:** Fri Nov 14, 2014 4:09 pm

Videos added. You probably will want to turn up your speakers as high as they can go. It is kind of a high pitched sound that sounds like a humm or a tone.

greiswig · **Posted:** Fri Nov 14, 2014 4:18 pm

Using my cheap headphones, I can't hear a difference from early in the video to late, where you say "Now." Turbo whine?

Where is the whine coming from? I've noticed that the wiring in my Jeep seems really susceptible to picking up RF noise, presumably because the preamp lines to the amplified speakers are not shielded.

SFHLibertyCRD · **Posted:** Fri Nov 14, 2014 4:37 pm

Its not turbo whine which generally corresponds to the rpms and sounds different (this has more definite on/off moments). Did you try both videos? It is barely perceptible and if you don't know what to listen for somewhat hard to catch. Almost can be mistaken for an artifact in the audio.

SFHLibertyCRD · **Posted:** Fri Nov 14, 2014 4:41 pm

Also, it's definitely new.

papaindigo · **Posted:** Fri Nov 14, 2014 4:53 pm

I'll be honest and say I cannot hear anything. That said have you checked the condition of the alternator decoupler pulley?

greiswig · **Posted:** Fri Nov 14, 2014 4:57 pm

SFHLibertyCRD wrote:

Did you try both videos?

Yeah, sorry. I could try it on my studio monitors when I get home, but from the sound of things, there is too much background noise. The human ear is amazing at picking these things out when they are coming from different locations, but if they are all coming from the same pair of speakers and it's not new to us, it's a different story.

Again, do you know where the noise is coming from? Is it definitely under the hood? Worse with the hood raised? If you unplug the fuse that powers the on-speaker amplifiers, does it go away? Could it be the clutch on the alternator, or even the brushes in the alternator going south and causing noise in the speakers?

SFHLibertyCRD · **Posted:** Fri Nov 14, 2014 5:59 pm

Greiswig and papaindigo,

The problem is I only hear the noise while driving (I tried revving the engine in neutral or park and it did not happen). So, basically, it is hard to isolate because I have to be in the cabin with the hood down and driving to hear it.

I guess I've been trying to narrow down whether anything that I mistakenly removed and reinstalled could be a clue. I definitely never noticed this sound before the work I did this weekend (much of it unnecessary, unfortunately) to get to the CPS. That, and whether spilled coolant might have gotten on something. I don't have the car in front of me to look, but is the alternator anywhere on the passenger side of the block where it might have gotten coolant spilled on it?

On a side note, I checked the play on the turbo when I had the hose off, and it is just rock solid. No perceptible movement that I could find. So, I guess that's good.

thermorex · **Posted:** Fri Nov 14, 2014 11:36 pm

I can hear the noise you're talking about, it's like a very thick, low tone whistle. I have something similar on mine and it started when I replaced the turbo hoses with samcos. I can only hear it on harder acceleration and in my case is definitely coming from the turbo. Could as well be a bearing going bad. Hard to pinpoint if it doesn't do it when the engine is not under load...

SFHLibertyCRD · **Posted:** Sat Nov 15, 2014 12:12 am

thermorex wrote:

I can hear the noise you're talking about, it's like a very thick, low tone whistle. I have something similar on mine and it started when I replaced the turbo hoses with samcos. I can only hear it on harder acceleration and in my case is definitely coming from the turbo. Could as well be a bearing going bad. Hard to pinpoint if it doesn't do it when the engine is not under load...

Well, that's not what I want to hear.

Why would replacing hoses, or in my case removing and reinstalling them cause something like this to start up? Also, how sensitive are the turbos when exposed like this? If, for example, a few drops of my coolant dropped in the inlet, would that cause an issue? It wasn't much, but I did wipe up a few drops of coolant at the turbo inlet when putting everything back together.

Like I said above, this turbo is very tight. No play at all. There was hardly even a mist of oil in the airbox to turbo hose. However, the turbo sound is very defined in my CRD (Jim/Geordi remarked on that when test riding with me after the TB change, and wondered about it). I'm very used to hearing that, but this sound seems distinctly different to me. I'll have to drive it some more and see if I still think that.

CATCRD · **Posted:** Sat Nov 15, 2014 10:32 am

I think the intercooler hose is not seated right or not tight on the outlet of the turbo. Happened to me once and caused a strange whine, also only under boost. That's your main clue - doesn't happen in neutral.

SFHLibertyCRD · **Posted:** Sat Nov 15, 2014 12:40 pm

CATCRD wrote:

I think the intercooler hose is not seated right or not tight on the outlet of the turbo. Happened to me once and caused a strange whine, also only under boost. That's your main clue - doesn't happen in neutral.

Thank you. I'll recheck my hose connections. How tight do they need to be?

SFHLibertyCRD · **Posted:** Tue Nov 25, 2014 3:24 pm

CATCRD wrote:

I think the intercooler hose is not seated right or not tight on the outlet of the turbo. Happened to me once and caused a strange whine, also only under boost. That's your main clue - doesn't happen in neutral.

And the winner is CATCRD. Thanks guys.

Popped the hood and there was a little oil residue up by the top of the intercooler hose and my Samco was clearly not seated properly up there. Rechecked all hose connections that I had removed and got everything buckled down well and it now sounds like it used to with no new noises at boost. This forum is awesome. (I clearly had no idea what I was hearing even though it was obvious given the symptoms and what caused it.)

ebbnflow · **Posted:** Tue Nov 25, 2014 8:48 pm

Glad to hear it is fixed. Thanks for posting what fixed it.

Help me diagnose this whine between 1800-2000 rpm

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