Engine Groan-like noise at 90K Miles

[turtle1026]

Lately I get a "Groan" from my engine as it passes through from 1400 RPMs to 2000 RPMs. I have ruled out axles as the problem because it occurs at a standstill or while driving. Basically, you hear normal engine sound as you accelerate and then it takes a different tone. After 2,000 RPMs the sound turns back to normal. I am at the 90,000 mile mark. I have maintained the vehicle well, but have not yet performed the BSM or TB change. I am suspecting that it is the motor mounts given that this sounds like a harmonic problem to me. I've looked at both motor mounts and I see no visible sign of wear. However, in my experience with other cars, mounts can compress or otherwise lose effectiveness. You can't notice it until you compare it to another brand new mount. Any advice?

 

[johnboy00]

It could be the alternator pulley.
It could be the fan bearing.
The motor mounts are fluid filled and you will see red fluid reside when they leak out.

More importantly it could be the BS module screaming that the tensioner is broken and all hell is about to break loose.

In all honesty, I wouldn't drive it until you can isolate the problem. Your engines life as well as bank account could be at risk.

 

[turtle1026]

I am pretty confident that it is not the alternator pulley. I had that problem in the past, and I replaced it about 30K miles ago. It was a different feeling altogether. Is a failing BSM typically identified by this type of tone change? After reading many posts I thought it would sound more like a chain rattling or other more nasty sound. This is really just a tone change in that small RPM band. With failing internals, I would expect it to be present in more than just that small band. The car runs fine otherwise. My fuel economy is around 33.5 with AC always on. It has been a while since I have cleaned the intake manifold, though. The power seems pretty normal. I do, however, feel like the engine is a little louder than it was originally. A "noise" is so hard to explain. Thanks for your response.

 

[edthacker]

I am voting on the Balance Shaft chain tensioner shot. My chained engine made a harmonic sound that I would describe as a "HUUUMMMMM" at those RPM ranges. MOgolf unchained it (150K) and now much, much quieter and smoother.
Don't put off the BSM! Disaster is around the corner if you wait.

 

[turtle1026]

A "HUUUUMMMM" is a great way to describe what I am hearing. It sounds like my next project is the BS/TB.

 

[passatpete]

A "HUUUUMMMM" is a great way to describe what I am hearing. It sounds like my next project is the BS/TB.

I had mine done at Gunthers VW in Coconut Creek, FL. They have the expertise to do it right. Good luck.

 

[maktas]

Its not the BSM, I have mine upgraded and I have exactly what turtle1026 is describing. It almost sounds like an exhaust leak of somekind. I also think that there is a more noticable engine hum at crusing speeds then from before my car reached 100,000kms

 

[whizznbyu]

when was the last time you changed transmission fluid?

 

[robertchaney]

engine noise

I have the same noise, thought it was the BSM-so I replaced that (117,000). Noise is still there. Only at low rpm, Alt. pulley is OK. What's this about Trans. fluid??

 

[leicaman]

I think getting it to a known guru would be a step in getting things sorted out here. Gunthers VW would probalby be familiar with the issue.

 

[whizznbyu]

my transmission fluid got the first ever change at 120K miles. It was making the same noise the author described, and when I changed the fluid, the drivetrain became quieter. I don't know if that did it, but I thought there was a significant change in the noise coming from the drivetrain before and after.

 

[turtle1026]

I have not changed the transmission fluid yet. I also agree that the sound is similar to an exhaust leak. I discounted the exhaust leak because it disappears at higher and lower RPMs. The sound is really only present in the 1400-2000 range. Since the noise is present while stopped, I never suspected transmission fluid. It doesn't sound like that could be the problem. I am still wondering about the motor mounts. I'd hate to change them with no visible leaks but I would think they are likely less effective now than when new.

 

[whizznbyu]

does this sound you're hearing make you think that the engine might have the equivalent of a "sinus congestion sound"? Mine has a different noise from 1500 to 2000 but it has to be at load; meaning at a hill or accelerating.

 

[thundershorts]

sounds like trans pump cavitation. low fluid or clogged filter

 

[turtle1026]

Problem Solved! I had someone rev the car while I checked under the hood. I was able to isolate the sound to the area around the air filter box. The box was picking up a strange vibration at those RPM levels. I could grab the box and the noise would stop. It turns out the lower portion of the air box (the part that holds the air filter) had come loose from its mount. The lower box mounts to the frame with 2 rubber grommets that press straight down into the steel. One side was not pressed in all the way. I am not sure how it happened so I will watch for it to pop up in the future. I have to believe it's from me not putting it back in correctly at some point. Regardless, I pressed it back in and the vibration has stopped.

Thanks for the help on trying to diagnose this. Hopefully, some of you who have had this sound can fix yours by making sure your airbox is properly pressed back into place.