Older 4.3 Stumps me

daevans315 · Post by **daevans315** » Wed May 31, 2006 3:38 pm

This is a video of a VERY high pitch loud noise coming from a friends 92 4.3. I'm sure that whatever speakers you have do not do it justice. It happens any time the engine is at idle and not under a load. It is coming from the engine compartment but I can't figure out where. This thing has 200,000 miles on it and runs good, you just need ear plugs. The middle of the video when the noise stops he just put it in drive and then back into park when it starts again.

http://www.ubergobbie.com/phone/index.p ... 0531185700

I'm still google'ing and asking other gear heads but I am completely at a loss.

top_sgt · Post by **top_sgt** » Wed May 31, 2006 3:43 pm

sounds like a vacuum leak of some sort.........would have to have the truck beside me to be sure. a noise that loud should be easy to find!!!!

daevans315 · Post by **daevans315** » Wed May 31, 2006 3:48 pm

top_sgt wrote:sounds like a vacuum leak of some sort.........would have to have the truck beside me to be sure. a noise that loud should be easy to find!!!!

Thats what I thought to.. but I took off the vacuum line to the brake booster and it didn't change pitch at all with that huge vacumm leak. Its such a high pitch and loud noise that I can't tell where its coming from.

04crewvt · Post by **04crewvt** » Wed May 31, 2006 3:48 pm

If the 92 4.3 has an air pump check if there is a leak in the tube running to the manifold (at least I am pretty sure it runs into the manifold) that could cause a high pitch whistle. Mind that this is only a guess.

Post by **HenryJ** » Wed May 31, 2006 3:51 pm

My connection is way too slow to check out the sound file.
Here is what I would do to trouble shoot it.

Take off the belt, or belts. If there is more than one remove one, check the driven accessory by hand feeling for dry or damaged bearings. Then start it and see if the noise is gone. Continue to remove belts if applicable and check the remaining accessories.

Starting the engine with the water pump not turning is not a problem, just don't run it for a long time.

The likely suspects are the tensioner pulley bearings. a weak tensioner, bad idler pulley bearings, bad water pump bearings, bad alternator bearings. Check them all for free play fore and aft as well as side to side. Feel for roughness or stiffness when rotated. Watch for signs of seepage at the water pump weep hole. The seals can fail when the bearings go bad.

Good luck

daevans315 · Post by **daevans315** » Wed May 31, 2006 4:07 pm

HenryJ wrote:My connection is way too slow to check out the sound file.
Here is what I would do to trouble shoot it.

Take off the belt, or belts. If there is more than one remove one, check the driven accessory by hand feeling for dry or damaged bearings. Then start it and see if the noise is gone. Continue to remove belts if applicable and check the remaining accessories.

Starting the engine with the water pump not turning is not a problem, just don't run it for a long time.

The likely suspects are the tensioner pulley bearings. a weak tensioner, bad idler pulley bearings, bad water pump bearings, bad alternator bearings. Check them all for free play fore and aft as well as side to side. Feel for roughness or stiffness when rotated. Watch for signs of seepage at the water pump weep hole. The seals can fail when the bearings go bad.

Good luck

I've run with the single serpintine(sp?) belt off... Still a noise.

daevans315 · Post by **daevans315** » Wed May 31, 2006 4:08 pm

04crewvt wrote:If the 92 4.3 has an air pump check if there is a leak in the tube running to the manifold (at least I am pretty sure it runs into the manifold) that could cause a high pitch whistle. Mind that this is only a guess.

No smog pump on this guy and I've run with the belt off with no change.

Post by **HenryJ** » Wed May 31, 2006 4:14 pm

daevans315 wrote:...I've run with the belt off with no change.

Things get harder now since we need to eliminate the transmission and torque converter as causes. Pull the dust cover and unbolt the torque converter. Watch for any clues that might be visible, like a starter problem, flywheel damage, rubbing converter, etc.
Once the converter is loose push it back as best you can and start it again to see if the noise is still there. If it is , removal of the engine would be the next step. I'd probably be looking for a spun bearing.

daevans315 · Post by **daevans315** » Wed May 31, 2006 5:47 pm

OK... Its fixed.. or at least band-aid'ed. Do you want the solution or should we give more people time to guess.

F9K9 · Post by **F9K9** » Wed May 31, 2006 6:26 pm

daevans315 wrote:OK... Its fixed.. or at least band-aid'ed. Do you want the solution or should we give more people time to guess.

I ain't guessing just looking at the map

You're to far way to choke for the answer

Post by **HenryJ** » Wed May 31, 2006 6:35 pm

Glad you solved your problem. Sorry we were of no help.
If you really want to make'em squirm , I can just delete the thread

daevans315 · Post by **daevans315** » Thu Jun 01, 2006 9:11 am

It was a pin hole leak in either the O-ring round the rod the throttle body butterflies pivot on or the seal between he throttle body and the intake. My wife came out and listened with earplugs in and used our fish tank siphon hose as a stethoscope to narrow down the location. Once the general area was found I figured out that moving \ twisting the throttle linkage without actually moving the throttle would change the pitch. Out of frustration mostly I sprayed the linkage and side of the throttle body with white lithium grease. Problem went away. I’m guessing that the grease either plugged the whole or swelled the gasket \ O ring enough to plug the whole.

I’ll see how long it lasts… guessing we will be putting a new o-ring or gasket in the throttle body before to long.

One to file away for later reference I guess. I am still amazed at how loud this thing was. You could not have a conversation over it. I actually had a neighbor come over this morning and ask me what I was doing that kept setting off the alarm…

04crewvt · Post by **04crewvt** » Thu Jun 01, 2006 9:55 am

Well I knew from the sound it was air, just didn't have the correct location

Guess you stumped all of us on this one. Glad you figured it out quickly though I wouldn't have wanted to be around that sound for long.