Juggalo

I just bought my truck about 1 month ago, and I'm just wondering why it's so loud when you first start it up, even when it's been off for 5 minutes and it's still hot, it makes a loud noise for about 20 seconds, than it goes away and it sounds smooth and quiet again.

I'm sure this is normal and you guys know what this is, can someone please explain what exactly makes this noise, and why?

Thanks

Juggalo

95_4X4Runner

It's caused by the fan clutch, and it's totally normal.

JSharp

If you close your eyes, you can almost imagine what it's like to be in one of those military hovercraft as the skirts inflate...

Jonathan

Oh yes the dreaded "my engine is about to take off" noise. My 92 PU did the same thing. Everyone asked me if my truck was about to blow up.

Juggalo

Thanks a lot guys, I knew it was normal, I just didn't know what caused it to do that.

But why does it only do it when you first start the truck up?

Juggalo

OneTrickToy

whoa... you guys are weird... my truck sounds fine at startup. I usually have to turn the air off to tell if my truck actually started or not. But on that note.....the engine was replaced around 100,000 miles by my anal retentive uncle. So it might just be that my engine is newer?

Robinhood150

Um, what does the noise sound like? Is it a ticking sound, screeching sound, wind sound, etc?

My 3.0 isn't loud for the first 20 seconds.

ByThaBay

I know the exact noise you are talking about, my truck has done it ever since it was purchased back in '93.

Personally, i really like the sound; i think it's cool and adds a really great sound to the vehicle upon startup.. sounds a lot meaner

i am not sure why it does this, but here is my theory:

when you are running your pickup, the engine is being cooled by the coolant/fan ... when you turn off the truck and then turn it back on after a few mins, you'll see that the temperatue guage will be slightly higher, this is becuase the coolant is not moving around and not being cooled off. Also, the engine is not being cooled at all, so all that heat is being dissipated by the block. I believe, that as a default, the engine is immediatey super cooled off on every start to prevent overheating.. but this is just my thoery, i don't know if it's the right reason for the sound or if there is even such a thing..

Babypig

As I live across the inlet from the coast guard that has a large hovercraft, I would have to say that you've hit the nail on the head.

mtnfreak

Well, I hope it's fan noise and not something that's knocking or grinding until it gets oiled up.

Highland Runner

Having my fan clutch apart many times to fix my overheating problem, I'll tell you why. When the engine is off, silicone fluid in the fan clutch floods the clutch plates (looks like a round maze). When the engine starts, the fluid is forced centrifically to the outside edges of the clutch where it is forced through 2 pin holes into the back of the clutch. During the time it takes the fluid to empty the clutch plates, the fan is fully engaged and spins at the same speed as the engine. That 's why its so loud, and it last usually 1 min or so. As the engine heats up (radiator gets hotter), the spiral spring on the front of the clutch turns a "valve" which lets this fluid back into the clutch plates, and the fan speed increases to cool the radiator. So most of the time drivng, air flow is enough to cool the radiator and the fan slips and doesn't make any noise. In stop and go traffic or hill climbs, you may hear the fan get loud again.