PapaHepcat

On my '99 Burb 2500 (7.4l Vortec), I'm hearing a distinct whistle from the front end. The whistling occurs in a small window around 1500 RPMs, regardless if I'm parked or driving. The pitch of the whistle rises as RPMs increase, and fade out right after 1500. And the noise mostly occurs when the motor is cold. Greatly lessens or disappears completely after the motor gets up to operating temperature. Here's a quick vid I took of it:


I'm thinking something connected to the belt. Water pump? One of the pulleys? Something else maybe?

mountainmanjoe

Sounds like a bad alternator to me.

I would slip the belt off, and turn each pulley by hand.

Rednucleus

You can use a piece of hose as a stethoscope to listen to each component in the are. PLEASE BE CAREFUL AROUND THE BELTS/PULLEYS ETC!!!
If it's the alternator it will be obvious listening with a hose

oilcanhenry

Dont know if its obivious, or any fault, but as soon as the A/C compressor kicked in the sound disappeared.

Cusser

If you can repeat/confirm that, then it sounds like the bearing in the AC compressor's clutch is going bad; with AC off, the outer pulley of the clutch spins on that bearing, but when the compressor is engaged then both the pulley and the compressor get magnetically locked, so you don't hear that as it doesn't turn.

Unfortunately (1) there is typically not enough space to just replace an AC clutch without first removing the compressor, so typically the fix is recovery of the refrigerant, installing a new compressor and appropriate amount of refrigeration oil, and evacuating/recharging with correct amount of refrigerant by weight. Most shops will insist on a new accumulator at this time as well.
(2) A new AC clutch will be pretty much same cost as that new compressor with its new AC clutch
(3) On some AC clutches the bearing can be removed and a new one tapped in; guess it depends how handy you are and what kind of refrigeration equipment you have.

oilcanhenry

I'm not the OP, but I saw the A/C compressor kick on at the end of the vid, and the sound went away. You are correct that a new A/C Compressor costs close to what the magnetic assembly costs. Unfortunately most DIY'esr cannot afford an A/C recycle machine, but then we were also promised that R-134A was _much_ less able to harm the ozone layer then R-12 was, and the new _flammable_ R-1234FY or "F-U" is, so dumping "Freon" to atmo never concerns me at all, as I am not a professional mechanic, just _almost_ became one. If I were, I would comply with the law,, but I am not, so it goes to atmo if that is what I need to do to repair an auto A/C system.

After all much or many of these auto airconditioners will slowly leak or they will get busted up in an accident, leaking the FREON to atmo, so why worry? $1000 dollars for a 30 pound bottle of R-1234FY which is now flammable, unlike R12 or R-134A? You gotta be frakking kidding me! We are once again being ripped off with high FREON costs with no indication that they help the environment in any way. Like always, its abou the $$$ and not about helping our planet whatsoever, at all.

Just to make it clear to the DIYers here, by law, you must dispose of your refrigerant(R-134A only) into a very expensive "Freon" recycling machine to remain completely legal. Its not cheap as you will have to take your vehicle to a shop with the recycling machine, and they will try to have you let THEM repair your A/C system, but you will pay hard. Not gonna hapen with me, as I have seen how the manufacturers of what I like to call "Freon" have been playing "Increase the price" since they did away with R-12 over 20 years ago now, replacing it with R-134A FREON. I have converted two vehicles to use R-134A, but I trained to become an automotove mechanic, specialzing in A/C repair and well as other repairs, many years ago now. I'll be damned if I ever use that R-1234FY in any car at all.

When I was young, you could buy R-12 FREON almost anyplace at .79 to .99 cents a 12 oz. can. Most system only use 3 cans of refrigerant to fill them up to operating conditions, some less, but vans tended to take a bit more then that. It was non-flammable and safe to use, much like R-134A is and was. Now, these laws and companies wish us to start using a FLAMMABLE refrigerant called R1234FY. Which is extremely expensive and could ignite under certain conditions. Too H**ll with that nonsense!

Cusser

My Ooops on YOU being the original poster. I'm now able to get the video to play, and still am firm on the AC clutch bearing noise as I detailed earlier.

As to your comments about refrigerant, I agree completely that the government blew it with R-12. As a scientist, R-12 worked great and is non-flammable. The issue was that being so available for Gomer and Goober back then, and its low cost, way to many would simply add a can refrigerant to a leaky system, and repeat that process; I'm not talking about the "one can in 3 years folks". I'm sure some backyard mechanics still do similar "add a can" temporary fix with their R134a vehicles.

I believe the current R134a regulations prevent professional mechanics from filling a leaky system with R134a except for use in the diagnosis of leaks. I would've made R-12 policy to be like that, and would've restricted the sale of R-12 to non-qualified individuals, like it is now in the USA. That alone, without additional engineering like that required for use for R134a, could've stemmed the R-12 issue.

As we know, R-12 was just one of the multitude of chemicals that can affect the atmosphere. Emissions come from burning of hydrocarbons, animal gases, methane from wastes, but primarily all is a result of overpopulation of the planet; none of these were real issues when there was less than a billion people. Who is going to give up eating/using animal products? Who is going to give up the Suburban they use for family vacation and use a small efficient vehicle 51 weeks and then rent the big vehicle for that 1-week use? Not many. And remember that getting rid of that older vehicle and replacing with new means that pollution is caused just by the manufacture and transportation of all those thousands of new parts.

The earth has forever had temperature cycling; in the Middle Ages there was a cooling period called the Little Ice Age, affected worldwide economies, crops, disease, wars, etc. https://en.wikipedia.org/wiki/Little_Ice_Age And then there were the true Ice Ages. The issue is very complicated; one big volcano eruption could throw the planet into a cold spell.

Understand that I think that some federally mandated safety requirements were good ideas. I like the safety switch on clutch pedals requiring that to be pressed down for starter to operate. I like the requirement for seat belts (but didn't like the required interlock system of the mid-1970s. I like mandated air bags, but I have 3 vehicles that do not have those (as they are 1970-1988); those do not have ABS, third brake light either.

73shark

I used an empty R12 bottle to recover about 90% of the R12 in my 87 IROC when I replaced the compressor. I set the R12 bottle in a bucket of ice which tended to the lower the pressure below the ambient R12 pressure. This obviously works better in the summertime when the system is warm and the R12 pressure will thereby be higher.

Cusser

I also recover my R-12 (my 1988 Mazda truck still has that, replaced seized compressor in that about 5 years ago). I have a canister that holds like 2 pounds. I pull a good vacuum on that, put that in my freezer. I make an ice bath from dry ice from grocery store and used/old coolant. I attach the center line of the service gauge set to that, loosen the fitting a tad and purge the lines with a little R-12 from the vehicle, then place the cold canister in the dry ice bath, and open the valves. The vacuum pulls R-12 over, which condenses to a liquid from the cold temperature, which keeps the vacuum, and more R-12 keeps coming over. Works for me.

I can similarly recover R134a.

73shark

Smart minds travel the same road together.

I considered attaching to the high side of the compressor and running it for a short period but wasn't sure what the high pressure limit on the bottle was and therefore didn't try it.