Ok, I know it's cold out but...
 

I know it's cold out but I need all you guys in the colder areas of our fine country to do me a favor. If it's about 25-30F or below in your area, turn the radio and the heat off (or at least to very low.) Go over any slightly bumpy or rough road, at any speed, and listen for a creaking/rattle coming from the area where the windshield meets the dash. I've got one so nasty it sounds worse than riding in a 10 year old Chevy Shakerado. It ONLY does it when it's below freezing or colder.

The dealer determined it's the plastic cowling outside (you know, the one with the free ice maker) and has since replaced. It doesn't make the noise with it removed; however, I'm guessing they only replaced it since they broke it when removing it. I'm still stumped as to why it goes away when it warms up. If something's rubbing when it's cold and contracted, why does it stop when it warms up and expands?

BTW, this an '04 Screw Lariat but the cowling should be common across the product line.

https://www.f150online.com/galleries....cfm?gnum=3470

As of right now the temperature is -39 below, -55 with the wind chill. I also hear this creaking the odd time, although I dont turn off overything to hear it.

My brother has an '03 Sierra that does that. I had a '91 Ranger that did it also. I would suggest living with it before letting them dis-assemble half the world trying to fix it. They'll probably just end up making a new rattle that rattles all the time.

Just a thought as a material scientist. i don't know how the cowling is anchored, but if the plastic has a Tg (glass transition temperature) around 32F, it may be contracting enough to stress whatever screws, flaps, or pegs that hold it in place. remember, polymers (rubber, plastic, etc) as a general rule expand and contract about 8 times more than metal over a given temperature range. this may be why the cowling is more stressed a low temps and makes funny sounds, but at warmer temps is all good. the metal that it is anchored to stay relative the same in dimension, but the plastic is contracting at low temp and stressing joints. there isn't much they could do about this except change the design of the cowling and how it is anchored to the truck. most plastics will have this problem with thermal expansion/contraction.

The cowl (plastic ice cube tray) has a "rubber" GIMP (Gap Improvement) seal that bridges the gap between the windshield and the cowl.

I would imagine that as temperatures drop, this "rubber" stiffens up, and begins rubbing a lot harder on the glass and the truck moves, causing a squeek, or creak. As things warm up, the "rubber" gets more compliant, and can now flex to conform to motion, rather than sliding.

Now, I'm not living with your particular situation, but I would advise living with it. If they replace the cowl, only two situations can arise: (1) The part fits exactly as before, and you end up with the same issue, or (2) the creak goes away, because the GIMP seal is not impinging on the glass as much (part fit is looser to the glass). In that case, you may end up with some Wind Noise being generated by the looser fit, especially as things warm up.

Hope that helps.:fyi: :fyi:

rubber is still very flexible at 32F. I should know, I am a the R&D manager at a rubber seals company. as you go below freezing, depending on what kind of rubber it is, it can get stiffer. most likely they use an EPDM rubber (poly(ethylene-propylene-diene monomer)) which does not become brittle until about -50C (-58F) so it is not likely that the seals are doing what you say. most likely they are shrinking. but if the GIMP seals are not actually rubber, but more like a TPE (thermoplastic elastomer) then what you say may be true. i guess it all depends on what kind of material they use. they should be using EPDM in my humble opinion, but parts like that are usually decided on price. oh well, good luck man.

:lol: @brewmaster. What arrogance.

:confused:
What's up with that? The thread involves stuff that BrewMaster has technical knowledge of and he happens to be sharing that with us. Some might not care, but there are others who do. If you're not interested, you can always move on. There's no need to take "shots" at people...this forum already has had enough sniping going on.

John

That's what's up with 'that'. An engineer stated above his reply what is happening, in detail.

my apologizes if it came off arogant, I didn't mean it to be so. i was just qualifying my comments, not putting anyone down. JScharton brought up the point about rubber stiffness, that is why I responded with that info.

Guys,

I know it's been a few weeks but Brew and Scharton's replies got me thinking. My truck has NO rubber between the cowling and the glass. Just butts right up there. I looked over a bunch of the F-150s at work (99-01s) and they all have a rubber piece in-between. Is my '04 supposed to have one or is this another el chepo move by Ford (E.G. the infamous missing underhood light.)

I'm not trying to be picky but this tank is really wearing on my nerves. After getting wet from a leaky moonroof, going crazy from the rear window rattle, having to jump start the dead battery three times (intermittent, undetermined 2.5 amp draw) this latest rattle is too much. It sounds worse than a Chevy and I'm embarrassed to show off my new truck.