I have noticed a lot of blazers run really loud when they first start up, but are fairly quiet once they are warmed up.

What causes them to be so loud when they're cold?

 

its called cold start my friend. 99% cars run at a higher idle at cold start. once the temp sensors tell the computer its at a desired temp it idles down.

Its also because these blazers fans are loud as heck. lol

 

On a cold start, if you let it idle, it can take the fan clutch 3 or 4 minutes, or more, to quiet down. Hold RPM up around 2500 and it should shut up in less than a minute or so. The fluid in the clutch needs to heat up, holding RPM ~2500 heats it up quicker.

 

That makes sense, none of my other cars have ever been that loud on a cold start, not even my old 78 k10.

The fans on this thing are loud, but it does warm up after only a few minutes.

 

Whoa wait. i didnt even know they had fluid? I thought the temp thing in them was similar like a manual choke (coil thing) on a carb? Well,my idea of it has changed now. lol

 

When the engine is shut down after reaching normal operating temperature, the silicone fluid within the clutch transfers from one chamber to another. It usually takes approximately 2-4 hours for this to happen. If you try to rotate the fan by hand when the fan clutch & engine are cold, it should be relatively stiff. When the engine is re-started, the fan spins at approximately 80% to 90% of water pump RPM causing it to “roar”. As the silicone fluid is redistributed evenly within the clutch, it gradually disengages and the fan begins to free wheel causing the "roar" to decrease. The fan will continue to free wheel until the air temperature at the thermostatic coil on the clutch reaches approximately150F. Internal components of the clutch gradually redistribute the silicone fluid and begin to engage the clutch. As the clutch engages, air flow is increased across the radiator allowing it to dissipate more heat. When air flow temperature across the coil reaches approximately 195F, the clutch becomes fully engaged and the “roar” becomes noticeable again. When the air temperature at the coil decreases, the clutch starts to disengage, and the cycle starts over. Think of the fan clutch as a “temperature regulator” or “thermostat” for the radiator.

Here's more: Hayden - Fan Clutch Tutorial - Part 1

 

Ha cool. I didnt know about this. thanks hook

 

I know some people like em but the noise drove me nuts. Took mine out and put in an electric fan. Amazing how much quieter. Also I noticed a slight power increase. Been over a year now

 

No argument from me on noise level Everything has pros and cons though. A fan clutch is simple, cheap, reliable and efficient. When it's engaged, it affects engine power and makes noise. Electric is quieter, and does not affect engine power. It is less efficient, more stuff to go wrong, more expensive to install, diagnose, and repair. As a result, the manufacturers use them only when they're forced to, (on EW mounted engines).

 

Agreed Captain, personal preference I guess