You think you know LT1's..answer this!

[z28marine]

Ok, ive posted on about 3 other message board about this problem ive been having and i get all different answers or no one knows. Ok, well, about 3 weeks ago i developed this loud annoying whistle/squeling sound coming from my car.
1. It tends to only show up when the car is hot, or its hot outside and my car has been sitting outside.
2. When the car is stopped and at low RPMs the sound is dismall, but once i give it throttle..to about 2000 RPMS it comes back.
3. the sound comes from underneath the engine..
4. ITS NOT THE ALTERNATOR. At first i though it could be the belt or a pulley, but i took the belt off and the sound was sill there. Then i thought it was the crankshaft pulley/balancer, but then i was told that it would not be making a whistling noise, but more of a growling noise..so i cancelled that.
5. Then i was told it could be the waterpump, but its brand new and i havnt had any problems with it, but i was gonna try and replace it anyway....
Well, i was just given a new peice of evidence... When i turned on the air conditioning the other day, the sound grew alot louder even when i wasnt moving. The sound went from unnoticable to loud. So, whatver is causing this noise, also uses the AC in some way. Now...the question is...what could it be? What could cause this noise??? i challenge you all to find out!!!!

[Joe 1320]

Re: You think you know LT1's..answer this!

Originally posted by z28marine
When i turned on the air conditioning the other day, the sound grew alot louder even when i wasnt moving. The sound went from unnoticable to loud.

The A/C clutch has bearings..... the pulley freewheels until the clutch engages, thus transfering the rotation to the compressor shaft. The additional load of the compressor would put an additional load on the bearings making the noise louder. The A/C system is a self contained system, it doesn't interact with any other system except the addition of a fan when the clutch engages and a computer generated increase in idle rpm. Also, the bearing clearances would be tighter when cold, increasing in clearance when warm, making more noise.

What has my attention is that you said it makes the noise without the belt. The only items that are operating without the belt would be an electricaly driven air pump, shaft driven water pump or an internal problem. None of the above would have anything to do with the A/C except that the A/C compressor would put an additional load on the crankshaft. If you have a sloppy timing chain sprocket, the additional load could create more noise, a bad front main bearing could be the the source of noise as well.

A mechanic's stethescope would help pinpoint the problem.

[Joe K. 99 Zeee!!]

Only a guess but I'll throw it out....

Have you had your accessory belt replaced recently? Maybe dirty pulleys and belt...it can cause squeeking that may get worse when it's wet outside.

[N20LT4Bird]

GREMLINS

[Al 96 Ram Air T/A]

Easy test...

This may not pinpoint the problem, but it can help eliminate sources.

Using a spray bottle filled with water, one by one, spray the belt contact points. Start from the top pulley, working your way down to the tensioner, the ac pulley, alternator pulley, etc. The sound will briefly stop if the point you are spraying is the cause. If nothing else, at least you can eliminate these as sources.

The alternator may be making noise as well. It's not uncommon for the alternator to make some noise as they age due to the heat wearing them out. Internally, there are numerous surfaces which can squeal if glazed or worn. Take it off and spin it by hand. Or, better yet, take it to a rebuild shop to have it bench tested at speed. They usually will do this free of charge.


Finally, it may be the AC clutch bearing as stated earlier. A little WD-40 strategically squirted may help to briefly silence the noise if that's the cause. Just be sure not to get any on the belt.

[markd79ta]

Everything Joe said about the AC is true. If it is the AC, you will also encounter the same problem when the defroster is engaged. Why it is is routed through the AC, I have no idea. Actually, I had to replace the unit in my '90 because of this problem. However, If you get the noise without the belt installed, that is not good! If you have a spun bearing, you will get a screeching noise especially when you give it some throttle. I rebuilt an '84 Bronco that when the throttle was hit or brought up to 2,000-3,000 RPM, it sounded like a squeaking fan belt. Well, when I pulled the oil pan, the main bearings were hosed, and pieces of the pistons were resting in the oil pan.

[wolfdogs]

didya check the AIR pump and connections?

[Injuneer]

I think most of you missed something in his original post....

HE SAID HE PULLED THE BELT OFF, AND THE NOISE IS STILL THERE.

At first i though it could be the belt or a pulley, but i took the belt off and the sound was sill there.

Wouldn't that rule out the A/C, alternator, belt, idler pulley and power steering?

That leaves anything that rotates, in concert with engine rpm... OPTI, water pump, timing chain, oil pump drive, crankshaft, cam, and seals related to those devices.

The AIR pump only runs briefly, so that would not seem a likely candidate.

[markd79ta]

Originally posted by Injuneer
That leaves anything that rotates, in concert with engine rpm... OPTI, water pump, timing chain, oil pump drive, crankshaft, cam, and seals related to those devices.

Yup, this is kinda what I was alluding to in my post. I hope its opti, timing, or water pump related; and not the cam, oil pump, or especially the crank mains. The air conditioner puts a load on the engine (crank) which will make the problem worse. Anyhow, when I had to diagnose the problem as I described above, I had a buddy hit the throttle with me listening to the oil pan; sure as ****, it was the main bearings Although, it was pretty self evident for me with the chunks of piston lying in the oil pan as the motor was tearing itself apart

[z28marine]

well...hopefully its not the pistons...i just changed my oil and no evidence of any metal in it...but who knows, and the car is running like it always has...but,i think it is the AC like stated before. I know when the belt was off the sound wasnt as loud, and i might have been mistaken about the sound at the time...im not positive but im hoping. I plan on testing tonight. But, i turned on the defroster too, and that also started the sound. The defroster runs off the same thing as the AC doesnt it? well, when the clutch is pushed down the sound is gone, but once i release the clutch, the sound comes back. So, it gets louder when the AC is on and defroster is on. The sound comes when the clutch is out, and the sound is only evident when the car is hot and its hot outside, making it possible the sound is the bearing like Al 96 Ram Air T/A said....so, how does the problem get fixed? I never use the AC as it is, so can i disengage it? or what must i do to fix this problem? Thanx alot sooooooooo damn much guys, you have helped alot.

[BAS]

umm

Originally posted by markd79ta
Everything Joe said about the AC is true. If it is the AC, you will also encounter the same problem when the defroster is engaged. Why it is is routed through the AC, I have no idea. Ac

Umm, this is for when you need to clear away
moisture on your inside window. If you didn't
have it on, you front window would be steamed
up and you wouldn't be able to see anything.

[z28marine]

Well, the sound has the same reaction to when the defroster is turned on as when the AC is turned on...the noise gets louder. So...how do i correct the problem???

[Joe 1320]

The A/C clutch is engaged when the defroster is turned on. It is all the same system. To disconnect, pull the harness connector going to the A/C clutch.

I'm going to suggest this one more time...... go down to the autoparts store and pick up a mechanic's stethescope. Start the car and start probing around. When the probe is placed on each item, the sound is transmitted to the headset. You'll know when you find the area of the problem as the sound in the headset gets louder. This will eliminate 95% of all this guessing.

[Injuneer]

Joe:

I've been following this topic for 3 weeks on various boards....

People are making suggestions like crazy, including the one you made, but I haven't seen him actually try and do anything to pin the problem down. He just keeps asking the question over and over and doesn't attempt to work on it himself....

Harsh, but after watching this float around the various boards for 3 weeks, it makes me wonder.

Fred

[z28marine]

The reason is that i keep asking different boards is because i keep getting different suggestions everytime, and i havnt had tht time to work on it. Last time i asked, everyone was sure it was a waterpump, but i dont want to go out and spend money on a new waterpump which i just replaced not to long ago, adn then come to find out its not that. I just want to be certain. Im asking alot of questions because im trying a process of elimination. Ill try the stethescope out first and see where it gets me. DOnt think that your suggestion are falling on deaf ears. Im just trying to get the maximum number of input so i know what i can do if its the AC, the crankshaft, the waterpump, etc. Sorry about dragging this one on. Ill let you know when i try the stethscope.