Weird chirping noise

[Kevdog]

I'm experiencing a very odd phenomenon in my '98 ML320. About a year ago, I started getting a high-pitched squealing noise very occasionally at start-up (usually in cold weather). It would squeal for about 15-30 seconds and then go away. I always assumed it had something to do with the radio since it sounded like high frequency interference or something, but it was so rare that I paid little attention to it.

About a month ago, it started happening more frequently, and not just during start-up – it will come and go during normal operation of the vehicle. The best way to describe it is the sound of a chirping bird – it flutters and chirps for a few seconds and then goes away and comes back. It sounds like it is coming from behind the dash on the driver's side, but it's a tough sound to isolate. I just had the harmonic balancer replaced, so I don't think that's it.

Could it be the e-box fan, or something else? Has anyone else experienced this? It's going to drive me nuts if it gets any worse.

[roadsession]

Originally Posted by Kevdog

I'm experiencing a very odd phenomenon in my '98 ML320. About a year ago, I started getting a high-pitched squealing noise very occasionally at start-up (usually in cold weather). It would squeal for about 15-30 seconds and then go away. I always assumed it had something to do with the radio since it sounded like high frequency interference or something, but it was so rare that I paid little attention to it.

About a month ago, it started happening more frequently, and not just during start-up – it will come and go during normal operation of the vehicle. The best way to describe it is the sound of a chirping bird – it flutters and chirps for a few seconds and then goes away and comes back. It sounds like it is coming from behind the dash on the driver's side, but it's a tough sound to isolate. I just had the harmonic balancer replaced, so I don't think that's it.

Could it be the e-box fan, or something else? Has anyone else experienced this? It's going to drive me nuts if it gets any worse.

The search function here works real well...

[dickiegoodman]

E-Box Fan.

Common issue.

Seach here, or mbworld.org or benzworld.org.

15 min DIY job.

Remove fan, clean and replace. Sound will probably stop. The replacement little squirrel blower is like $150 (ouch!). I decided not to replace. Clean and reinstall.

My noise stopped shortly after cleaning.

Dickie
00 ML 320
97 328i
87 325is

[Kevdog]

Originally Posted by roadsession

The search function here works real well...

Yeah, yeah, yeah. I did search for it first which is where I got the clue that it could be the e-box fan, but I saw Gilly post something about an aux. water pump that made me think it could be more serious, so I thought I'd ask.

Thanks for the input everybody.

[Kevdog]

I followed the directions on cleaning the e-box fan from Ken Yee's site, and the noise has gone away for now. I noticed though, that on step 8, he says "I also lubricated the bearings (per Wolfgang)". I don't see anything on Wolfgang's site that mentions lubricating the bearings. Can anyone tell me how to do that? I couldn't even get the electric motor out of the plastic enclosure (it seemed like it would be difficult to do without damaging the plastic fan, so I didn't push my luck), but even if I was able to do that, I don't know how to lubricate the bearings.

I'll probably replace it with the newer model fan eventually, but I have to get the auxiliary fan fixed first, so I'm hoping the existing e-box fan can limp along for a little while.