Another unidentifiable noise...

APC9199 · **Posted:** Tue Jan 16, 2018 11:37 pm

I've been trying to figure this out for awhile and cannot seem to nail it down.

The noise comes from the engine bay, almost certainly the passenger side.
It only happens (noticeably) above about 50, maybe 55, miles per hour.
It only happens under load and goes away when I back off the throttle even just to maintain speed. ANY throttle makes the noise appear. Removing throttle at all makes it go away.
If I drive on the highway with cruise control on the noise appears going up even the slightest grade and goes away as soon as the road is flat again. It is very sensitive!

Now the fun part, internet sound charades!

The best way I can describe the noise is almost like someone sitting in the engine bay while I'm driving, sucking through the straw of an empty cup. That gurgling noise...but muffled. It also kind of sounds like a high-speed bearing with no lubrication when they get that "rattly" kind of sound. Skip to 1:40 in the following video to get an idea of what I mean...when he spins the bearing by hand. Also, that video is kind of fun...sorry to those of you who end up on a 2-hour Youtube binge after watching that! The noise does not sound like an actual sucking sound like a vacuum leak, it is more mechanical but very inconsistent...coming and going in spurts as long as the throttle is pressed. It also doesn't sound as distinct as a failing bearing. It is a strange sound that I can only relate to those things for lack of a better description. It isn't loud enough to record and post for you to hear either. Sorry that conveying the sound isn't easier...I just know something is going to fail eventually and probably leave me stranded in the desert.

https://www.youtube.com/watch?v=BN7ATpnGQW0

Now, some things to consider. The turbo is NOT OEM. I didn't realize it when I bought it, but it is obviously a no-name turbo. There are only a few markings on it to identify it and I have not tried. The shaft seems like it is in good shape and the vehicle has made this noise since I bought it at 88k miles. It has 115k now. If the turbo were failing it would have done it by now. I'm not saying it ISN'T the turbo, but it doesn't seem like a failing component if it is. Is there anything else in/on the turbo that might make this noise. even if the turbo is generally healthy? A seal that is leaking at 55+ mph for some reason? Could the vacuum solenoid or modulator make any sounds at higher speeds? I just rebuilt the top end from the head gasket up. I was thinking I would find the problem somewhere along the way and be able to eliminate it, but it is back now that things are back together. EVERYTHING has a new gasket, most of them with high temp RTV or copper-coat gasket sealant. I can't see or hear any leaks (or see evidence of any) of any kind under the hood. CAC hoses, air box to turbo hose, CCV to turbo, etc, are all well clamped and sealed from what I can tell. I re-seated the EGR end-cap on the exhaust manifold with a generous amount of high temp RTV as well, while it was off. Injectors are not leaking. I can't think of anything else in that area that might make this noise!

Does anyone have any ideas of how I could start eliminating possibilities without throwing tons of money at replacing random parts until I find it (possibly including the turbo)??? I obviously have no way to get under the hood at 55 mph to locate it under load when it seems to be making noise. Any help would be appreciated. If I don't find it soon I'm going to wrap the Jeep around a tree and call it "fixed"! haha! :twisted:

GordnadoCRD · **Posted:** Wed Jan 17, 2018 2:19 am

If it doesn't happen unless you're moving at speed, it's unlikely to be the engine.

Have you checked for air seal problems, such as the front of the passenger door seal?

APC9199 · **Posted:** Wed Jan 17, 2018 9:17 am

GordnadoCRD wrote:

If it doesn't happen unless you're moving at speed, it's unlikely to be the engine.

Have you checked for air seal problems, such as the front of the passenger door seal?

That thought had crossed my mind, but the fact that it comes and goes with the throttle so sensitively makes me think it can't be an air seal problem. Holding speed on a flat road it doesn't make noise or maybe only a few spurts here or there. Add 1% throttle and it starts to make noise. Remove that 1% throttle and it goes away again. If it were an air seal problem it would be constant at a constant speed regardless of throttle position. I can get out some masking tape and start covering areas one at a time to see if anything changes. That is cheap!

WWDiesel · **Posted:** Wed Jan 17, 2018 9:40 am

Check the turbo intake hose between the turbo and air filter box for cracks or loose connections! :idea:

APC9199 · **Posted:** Wed Jan 17, 2018 12:07 pm

WWDiesel wrote:

Check the turbo intake hose between the turbo and air filter box for cracks or loose connections! :idea:

Again, the hoses are all good. I have had them all on and off a dozen times or more since I bought it and I have replaced the air box to turbo hose once. The sound has never changed. I also changed the OEM CAC hoses to IDParts ones a few thousand miles after buying it.

flash7210 · **Posted:** Wed Jan 17, 2018 1:15 pm

Maybe its a front hub or axle bearing noise?

APC9199 · **Posted:** Wed Jan 17, 2018 5:07 pm

I suspect the front differential is heading south on my CRD. I can feel a bit of an out-of-balance type vibration at highway speeds. The wheel bearings are all fairly new. The problem is finding a shop competent enough to work on a differential without the old "its cheaper to just replace the whole thing" spiel. I don't trust myself to rebuild the front differential by myself yet, so I'm going to have to find someone who can. In any case, I suppose its possible that the noise is coming from the front diff and only appears under load.

Any other ideas?

GordnadoCRD · **Posted:** Wed Jan 17, 2018 6:54 pm

This may sound completely nuts, but check your motor mounts. When they go through the process of failure they can make all kinds of weird noises that Don't sound like motor mounts! For example, a little too much movement of the mechanical fan inside the shroud... and on... and on... It's worth checking.

APC9199 · **Posted:** Thu Jan 18, 2018 12:07 pm

I paid particularly close attention this morning on the way to work and noticed that the noise isn't heard until the 5th gear shift at the speeds mentioned earlier, 50-55mph. I think I can faintly hear it just below the shift point, but it is very quiet. As soon as it shifts it gets way louder. It wouldn't make most people notice, but it is very obvious to someone who drives a CRD on a daily basis. If it were the turbo, what about shifting into 5th would make it louder? I can see how it could be something in the front diff maybe, and shifting into 5th is putting enough strain on the system to make it stand out. I'm also starting to wonder if it could possibly be something with the transmission and maybe I'm just hearing it coming from the general passenger side area. My fluid levels are good, but maybe its time for a trans fluid change. I need to get a better torque converter in there anyway!

WWDiesel · **Posted:** Thu Jan 18, 2018 12:27 pm

APC9199 wrote:

I paid particularly close attention this morning on the way to work and noticed that the noise isn't heard until the 5th gear shift at the speeds mentioned earlier, 50-55mph. I think I can faintly hear it just below the shift point, but it is very quiet. As soon as it shifts it gets way louder. It wouldn't make most people notice, but it is very obvious to someone who drives a CRD on a daily basis. If it were the turbo, what about shifting into 5th would make it louder? I can see how it could be something in the front diff maybe, and shifting into 5th is putting enough strain on the system to make it stand out. I'm also starting to wonder if it could possibly be something with the transmission and maybe I'm just hearing it coming from the general passenger side area. My fluid levels are good, but maybe its time for a trans fluid change. I need to get a better torque converter in there anyway!

If it were associated with the turbo, one would think it would be noticeable in some of the other gears as the turbo spools up under load??? :roll:

Only in 5th or overdrive TC lockup?

flash7210 · **Posted:** Thu Jan 18, 2018 12:29 pm

Assuming that you are accelerating into 5th gear at a moderate and gentle rate, engine rpm drops and turbo speed drops accordingly after the shift. However, the speeds of your driveshafts, axles, gears, wheels, and bearings all continue to increase.

So, probably not the turbo.
Also, not likely to be the transmission.

Probably the easiest thing to do is to drain the front differential oil into a pan, then shine a flashlight onto the oil to look for reflections of metal flakes.
If there are metal flakes in the oil then something bad is happening to the bearings and gears.

Another thing you can do is grab the front CV axle where it attaches to the front axle. Give it a wiggle. Excessive movement is not good. A little is ok but a lot is bad.

All this implies that the noise you are hearing is coming from the front axle area. But as Gordonado has pointed out, it could be something else entirely.
Heck, it could even be a bad tire.

Edit:
And just to clarify, a CRD with stock TCM programming will not shift into 5th until about 62mph.
At 50-55 mph, the transmission is already in 4th and the shift you feel is usually the torque converter lockup clutch being applied.

APC9199 · **Posted:** Thu Jan 18, 2018 3:09 pm

flash7210 wrote:

Assuming that you are accelerating into 5th gear at a moderate and gentle rate, engine rpm drops and turbo speed drops accordingly after the shift. However, the speeds of your driveshafts, axles, gears, wheels, and bearings all continue to increase.

So, probably not the turbo.
Also, not likely to be the transmission.

Probably the easiest thing to do is to drain the front differential oil into a pan, then shine a flashlight onto the oil to look for reflections of metal flakes.
If there are metal flakes in the oil then something bad is happening to the bearings and gears.

Another thing you can do is grab the front CV axle where it attaches to the front axle. Give it a wiggle. Excessive movement is not good. A little is ok but a lot is bad.

All this implies that the noise you are hearing is coming from the front axle area. But as Gordonado has pointed out, it could be something else entirely.
Heck, it could even be a bad tire.

Edit:
And just to clarify, a CRD with stock TCM programming will not shift into 5th until about 62mph.
At 50-55 mph, the transmission is already in 4th and the shift you feel is usually the torque converter lockup clutch being applied.

OK, so it must be the torque converter lockup then. Noted. That is precisely when the sound appears noticeably and abruptly. I'm going to see if I can schedule a shop to inspect the front diff. I don't have the time or knowledge right now, unfortunately.

DieselJeepLuvr · **Posted:** Fri Jan 19, 2018 10:13 pm

Definitely drive train related. Your torque converter could be ready to fail or the flexplate could be coming apart. Both would cause this. If it were a U-joint it would be worse when decelerating.

GordnadoCRD · **Posted:** Sat Jan 20, 2018 12:55 am

DieselJeepLuvr wrote:

Your torque converter could be ready to fail or the flexplate could be coming apart. Both would cause this.

If the sound has come on gradually getting louder with time and miles I'd look to the torque converter area, if it started suddenly then got worse, the flexplate would be more likely.

APC9199 · **Posted:** Mon Jan 22, 2018 12:18 pm

OK, another update. I'm dropping the Jeep off today to have a shop check the entire driveline for problems and listen to the noise with me in the vehicle. I have had some vibrations on the highway that I suspect are from the front diff, so they are going to look strongly into that. I'll mention the TC and flex plate ideas, though I'm not sure they'll be able to inspect any of that today.

On another note. I climbed under the Jeep for the first time since the rebuild. I used to have a completely coated undercarriage from the turbo return line leaking. Unfortunately, I still have a small leak coming down the back of the turbo. I'm guessing this is the seal for the turbo? I'm guessing this seal, leaking, could also make a "gurgling" noise like someone sucking on a straw in an empty cup??? A new turbo might be in my future after all...

flash7210 · **Posted:** Mon Jan 22, 2018 2:30 pm

The oil leak from the turbo could be the gasket where drain pipe attaches to the bottom of the turbo or could be the oil feel line on top of the turbo.

Of all my years working on engines, not once have I heard a oil leak make any kind of sound. At least not any sound that could be heard over the noise of the engine.
Which is not to say that there couldn't possibly be anything wrong with your turbo. Rather that whatever you are "hearing" is not the sound of leaking oil.

APC9199 · **Posted:** Mon Jan 22, 2018 2:46 pm

I just got done removing and re-installing the turbo with a great amount of care paid to the return line gasket and feed line crush washers. I even used high temp rtv to help seal both sides of the return line gasket. I'm pretty confident that it is not the feed or return line. I wasn't thinking that the oil leaking was making noise, rather the pressure from the intake side was leaking through the seal and the oil was making the air "gurgle". I'll admit that I do not know the inner workings of a turbo in great detail, just the theory of them. Perhaps what I am thinking isn't even possible, I don't know.

I'll keep everyone updated with any findings as I continue to drain my bank account solving this problem! :dizzy:

GordnadoCRD · **Posted:** Mon Jan 22, 2018 5:28 pm

APC9199 wrote:

I just got done removing and re-installing the turbo with a great amount of care paid to the return line gasket and feed line crush washers.

Sorry to pick a little more from your bank account, but NEVER re-use the feed like crush washers. ALWAYS install new ones.
(Or you WILL have a leak there)
Oil leaks and exhaust temperatures don't play well together.

APC9199 · **Posted:** Tue Jan 23, 2018 8:29 am

GordnadoCRD wrote:

APC9199 wrote:

I just got done removing and re-installing the turbo with a great amount of care paid to the return line gasket and feed line crush washers.

Sorry to pick a little more from your bank account, but NEVER re-use the feed like crush washers. ALWAYS install new ones.
(Or you WILL have a leak there)
Oil leaks and exhaust temperatures don't play well together.

That is exactly what I was saying. I did not reuse ANY gaskets, o-rings or otherwise during the top end rebuild I just did. Every gasket and washer from the head gasket up is brand new right now. There is a drip down the back side of the front turbo housing and it does not look like it starts at the feed line. I will have to get a closer look to confirm, this was just me laying under the Jeep looking up at it.

APC9199 · **Posted:** Wed Jan 24, 2018 5:13 pm

So the shop came to essentially the conclusion I did...that the front differential is probably failing. Carrier bearings are their most likely culprit, as expected. I'll be able to talk to the tech who worked on the Jeep today and find out exactly what he is thinking, and what the cost will be to get it repaired by them. What kind of numbers should I be expecting for a front diff rebuild?

I think I'll get this service done and see what happens with the noises and vibrations, then update this thread again. They didn't seem to think the noise that prompted this thread was related to the drive train, but that remains to be proven. The saga continues!

Another unidentifiable noise...

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