“Gusty wind” sound on the highway.

[dreamer2355]

If the fan clutch is not disengaging at highway speed, it will sound like a jet airplane on some vehicles or sound similar to the issues your having. Do you have a scan tool to see what the coolant temp is at highway speeds or does the temp gauge on the cluster look like the coolant temperature is lower than normal at highway speeds?

Also check the weather stripping too and check to see if you have any doors sagging that could be contributing to excessive road noise heard in the cab.

Topic

[spelunkerd]

Thanks for the quick reply. Coolant temp is normal, at least with the gauge on the dash. I didn’t notice if it’s cooler than normal on the highway. The scan tool I have just shows codes, and there are no codes to read. You make a good point about weatherstripping. But that gusty noise happens even when there is no wind, which has me a little confused. I could be getting ahead of myself but it sounds like the fan clutch can’t disengage at highway speed, with sound caused by wind through the radiator meeting the resistance of a fan that can’t spin fast enough. I’m not sure how that works during a hot day when the clutch should be engaged. Is there supposed to be an automatic slip when wind speed exceeds fan speed? I’m feeling inclined to take it for a drive with the fan removed to see if the sound goes away. I think I could get away with that if I don’t have to idle long….

[Tri9SS]

I agree with dreamer, you say it does it even when not windy but in fact you are getting the same effect because the vehicle blasting through the air is the same as if the truck is sitting still in a strong wind. also check the weather strip at the back of the hood at the bottom of the windshield. The one the hood would press against. Are you getting the sound through the vents.

[spelunkerd]

Thanks for your input! I’ll check out those ideas and report back. I guess it could be a vent, but the gusty sound is new, so if it’s a vent then something is flapping more than it should.

[Matt]

If you happen to have a scan tool, take a look at fuel trims. I worked on a friend’s Trailblazer that had the electric fan clutch, and the relay had gone bad. She complained of a similar noise, and I did a little research, and that was the first thing I checked. It also set a code, so when I went to clear it, I looked over the live data. LTFT was adding about 9 percent because the fan clutch failed in the fully engaged mode. The short term was pulling fuel out, compensating for a bit less load on the engine. Long point short (too late) if the clutch has failed, it will add some extra load to the engine, and effect fuel economy.

[spelunkerd]

One day I’ll have to upgrade my little scan tool to retrieve live data streaming. Any suggestions about the best choice for general mechanics?

[EricTheCarGuy]

Anytime you have a noise it’s always a good idea to verify it’s origins first. As for testing the fan you might just try moving it with your hands with the engine off to see if you encounter any resistance, if you don’t then your fan is probably bad. As for the noise if you suspect the fan you might consider removing it and then taking it for a short drive to see if the noise goes away, if it does then the fan may be at fault but if not you will know to keep looking.

[spelunkerd]

Here’s an update regarding the “windy noise” problem. I put the vehicle onto rear jack stands and reproduced the sound with the rear wheels spinning and the vehicle in drive. Then I carefully listened under the vehicle with a long tube, and discovered that a grinding, clicking noise was coming from the transfer case, even with the car in 2WD. I pulled the case out and discovered that the rear main bearing inside the transfer case was trashed.

Although I would have liked to do all of this myself, we need this car working within the week, so I wimped out and took it to a specialty gear shop who are doing a partial transfer case rebuild for me. I videotaped everything that I did, and I’ll post it under my name (spelunkerd) on youtube in a couple of weeks.

Thanks again to all of you who contributed to this thread. You guys are great.

[dreamer2355]

Thanks for the update! Dont forget to link your Youtube video here for others to see C8-)

[EricTheCarGuy]

Oooh that’s interesting, I’m glad you took the time to track down the noise. Post a link here when you get the video up and don’t forget to turn the traffic light to green when the issue is resolved.

[spelunkerd]

Here’s the video showing the sound, the inspection, the diagnosis, and removal and replacement of a partially rebuilt transfer case. Thanks again.

http://youtu.be/yvZlmjLV4zE

Dave

[dreamer2355]

Nice video!

[EricTheCarGuy]

Awesome video, I think you should post a link to it in the ‘Repair Central’ forum as I know it would benefit others. Seriously, well done.

[Author]

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