I'm starting the dash teardown project to fix a malfunctioning blend door, but the primary reason I'm doing the project at all is to fix a squeal in the front center of the dash near the windshield defroster outlets. The squeal, which my daughter says sounds like a turkey gobbling, only occurs after the truck has been driven for about 3 miles and only at 2500-2800 RPM. The noise, which by the way is maddening, is not coming form the instrument cluster and seems to be coming form the front center at the defroster outlets. I'm hoping that someone out there who has had their dash apart might know what in the world is up there to be causing this racket. My fear is to get the dash apart and not be able to fix it, and then have to take to Ford anyway to get it fixed. Thanks ahead of time for any responses, this is an awesome board.

Greg
1999 4x4, Reg Cab

 

Does it matter what fan speed you have your system set to?

FYI: the defrost door is always "partially open" to assist in the prevention of windshield fogging, so the noise may be centered around that.

 

The noise is independant of the enviormental system. It's always present, the heater/ac controls don't effect it.

 

Maybe this would be better in the general discussion if it's not HVAC specific.

 

Thanks Corpsie I'll try that.

 

You more than likely have a leak in the windshield seal. Remove the plastic cowls at the base of the windshield. Get some black silicone, and run a bead at the bottom of the windshield. I have had this issue a couple of times.

 

The noise is RPM specific, only between 2500-2800 RPM. At 75 mph and 2600 RPM the noise is obnoxious, as soon as I engage the clutch the noise is gone.

 

Looks like you just diagnosed your noise. Why would the noise be coming from the dash if it is RPM specific? Which clutch are you talking about? The a/c clutch or the transmission clutch? Can you make the noise happen when the truck is stopped?

 

You ask a very good question and I'm not sure. The clutch that I make reference to is the transmission clutch, and yes with the truck standing still and in neutral; 2500-2800 RPM causes the same obnoxious gobbling noise from the front center dash...but only after the truck has been warmed up, before then no noise at all. Is there an HVAC vacuum manifold in that vicinity?

Thanks

Greg

 

Sounds to me like a throw out bearing noise. See if you can hear it from the outside, under the truck.

 

I've checked everywhere I can think of outside the truck, transmission, clutch housing, engine, cowl, no noise...it's definitely in the front center of the dash. This noise, whatever it is, is not effected by clutch position, speed of the truck, or HVAC settings

 

I thought you said as soon as you engage the clutch the noise is gone. Sounds clutch related to me.

 

Nope, clutch position makes no difference. Sitting in my garage without ever touching the clutch I get the noise at 2500-2800 RPM

 

 

The reason I made that statement was to illustrate that it was not a windshield wind noise. At 75 mph and 2600 rpm the noise was present. As soon as I engaged the clutch and the rpm droped to 700 rpm the noise was gone even though the truck was still doing 75 mph