Where is that sound of rushing air coming from?

[letsgo]

I'm not concerned just curious.

When the temperature drops below 32*F I start the Dmax first thing in the morning, It sounds like a noisy diesel, not a problem, but when I start driving down the street I hear this loud sound of rushing air this is at an speed between 15mph to 35mph or accelerating, if I take my foot of the accelerator the loud sound of rushing air disappears, this happens untill the truck starts to warm up.

Thanks for any input.

[BigLakeDMAX]

Could it be the engine driven cooling fan? A couple of my old trucks (97 6.5l and 88 5.7l) would both do this when they were cold (usually well below 32* however). WHen I checked on this on the 88, I was told the fluid in the fan clutch would settle overnight and thicken in the cold, and lock up the fan clutch so it would engage the fan 100%, just as it does when it's hot. After a few minutes of driving, it would unlock and quiet down. It was a very loud rushing sound, most noticable on acceleration at lower speeds. It also varied in intensity with engine speed. If you stood by with the hood open where you can see the fan and feel and hear the air flow while running the rpms up a little after a cold start, that would let you know for sure.

Just a thought...

Don

[letsgo]

BigLakeDMAX

Hmmmmm

I'll check it tomorrow morning

thanks

[Amianthus]

Probably the engine fan. No doubt in my mind.

[Rebel_Horseman]

I'm going to have to agree. On my way to work this morning it did that. I even let my truck idle for about 5 minutes to get all the juices flowing. It only blew for a minute or so.

Reb [><]

[WKener]

I don't own a DMAX, but you are describing exactly what happens on my Dodge on cold mornings (fan clutch engaged). I also have this happen on my other vehicles from time to time when it is quite cold, and it is nothing to worry about smile.gif

Everybody seems to have it properly diagnosed.

[letsgo]

I started the truck up this morning (25*F).

As you all said the fan was turning slowly and after about 2 minutes the fan speed increased (engine RPM the same).

I would conclude that there is a certain cold temperature that prevents the silicon fan clutch from slipping (lock up) as there is a certain hot temperature (lock up).

That explains why our diesels up north require the factory brazzier, to keep the cold air away from the engine fan other wise we would freeze to death (no heat).

Thanks for the input.

[needbigtruck]

It is the fan. If you haven't read it yet, or no one's told you it is quite dramatic when it engages under load. It has only happened to me last summer pulling my 31 foot TT down south. It really gets your attention.