Engine sounds like a 747 on take-off.....

dhawke · Post by **dhawke** » Tue Mar 11, 2003 2:55 pm

What gives with the engine when it's cold? I've noticed that sometimes, not all of the times, when I first start the truck the engine roars like it pulling in enormous amounts of air for the first 30 seconds or so. It has absolutely no power for all the noise it makes. Then...it quiets down and runs normally for the rest of the trip, however long that may be.

If it did this all fo the time when it was cold, or had been sitting for a while, I guess that I would just assume that is a normal operational thing. But, there really doesn't seem to be any real logic to when it happens.

Anyone know what is up with this??

AZS10Crew · Post by **AZS10Crew** » Tue Mar 11, 2003 4:22 pm

Not sure exactly why it happens (Brule could probably help with that), but the roar you're hearing is the fans running at high speed. Like I said...not sure why this happens at startup, but the 92 4.3 I used to have did the same thing at start up, so I'm used to it.

anvil · Post by **anvil** » Tue Mar 11, 2003 6:38 pm

I have the same noise, sometimes it lasts longer than other times.

Every 4.3 I've had in the past did the same. I never did ask what it is.

Probably is the fan, as that is the sound it makes.

Post by **HenryJ** » Tue Mar 11, 2003 6:51 pm

You guys got it right.

That is normal. The oil in the clutch tends to settle when they sit still. When you start it it takes a little while for centrifical forces to equally distribute it. Basically the clutch is locked up and then frees itself.

If you ever get it hot enough you'll hear the clutch lock and the rushing sound too.

Here is another thread: Electric fan

Jim · Post by **Jim** » Tue Mar 11, 2003 6:55 pm

anvil wrote:I have the same noise, sometimes it lasts longer than other times.

Every 4.3 I've had in the past did the same. I never did ask what it is.

Probably is the fan, as that is the sound it makes.

My understanding is: the fan clutch has a turbine like a torque converter when it is cold out the oil is thick & it will spin almost direct drive until the oil spins out by centrifugal force.

dhawke · Post by **dhawke** » Wed Mar 12, 2003 1:15 pm

That makes enough sense for me. So...the feeling of it having no power is just in my head. I mean other than the parasitic losses of having the fan directly connected to the motor...I half suspected that all along.

Thanks for the info guys!!

anvil · Post by **anvil** » Thu Mar 13, 2003 6:32 pm

Thanks for the reply. It is kind of funny that I never asked any GM tech. what that noise was.

Does it harm anything if I drove off a wee bit fast while I hear that noise?

Post by **HenryJ** » Thu Mar 13, 2003 6:39 pm

anvil wrote:Does it harm anything if I drove off a wee bit fast while I hear that noise?

I would'nt think so, it is designed to lock-up when it gets hot enough too.

Might slow your launch a bit though with the fan robbing HP

TNC · Post by **TNC** » Wed Mar 19, 2003 10:46 pm

I have the same problem. Actually it is more of a pain than anything else. I was told by a GM service tech that it is "just the engine pushing fluid through it" and when it is warm it just fine...

quickbiker · Post by **quickbiker** » Thu Mar 20, 2003 4:18 pm

They'll tell you anything!

Nate · Post by **Nate** » Mon Dec 08, 2003 6:03 pm

i was told it was a form of engine "choke"

a2b · Post by **a2b** » Mon Dec 08, 2003 6:35 pm

quickbiker wrote:

They'll tell you anything!

oh my...how did you dig this thread up??? and then you responded to it

quickbiker · Post by **quickbiker** » Mon Dec 08, 2003 7:44 pm

a2b wrote:
quickbiker wrote:

They'll tell you anything!
oh my...how did you dig this thread up??? and then you responded to it

Ha, that response is dated Oct 2002!

Nate · Post by **Nate** » Mon Dec 08, 2003 8:41 pm