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View Full Version : Random squealing sound when A/C is on


rob99rt
05-14-2015, 01:44 PM
I just replaced the serpentine belt (had a Goodyear gatorback and replaced it with a Gates belt) and I'm still getting a squeal/squeaking sounds sometimes when the A/C compressor is engaged. It's not the blower motor as I can (when it's actually doing it) make the noise start and stop by hitting the button to turn on the compressor. I drove to town and back the other day without it making a peep (about 45 miles), but my wife said it did it to her several times yesterday when she was driving to town when she tried to turn the A/C on. As such, she'd just turn it off and try again later.

FWIW, it's a 2004 that has right at 84K miles on it, and it has not had any of the idler pulleys or tensioner replaced. The tensioner seemed to be ok when I changed the belt out last week as I had to get a pretty decent lever arm in place to take the tension off of the belt. The top small idler pulley I could very slightly move back and forth if I grabbed the top and bottom of the pulley and "rocked it" back and forth, but it spun easily and would go for a while once it was spinning... I can't remember if I checked the others, but that one I know I checked.

Could this be a clutch or bearing issue on the compressor? If so, how would I diagnose which it is? I *really* hope the compressor itself isn't going bad. The A/C does work (although it takes a LONG time to cool down that big of a van with just a front A/C unit).

Any suggestions?

I plan to remove the belt this weekend and see if I can detect any wobble/dragging/noise in the compressor pulley, but is there anything else I should look at?

Thanks for the help.

jmoller99
05-15-2015, 01:20 PM
In my experience, the front AC really only does a good job of cooling the front seat area.

Did someone recently recharge your AC? If its overcharged, the belt can slip and you'll get squealing/chirping noises from the drive belt when running the AC. You can vent off some of the coolant and see if that helps. I had this problem when I was in 100+ temps outside of Colorado (the areas I go to where I live don't get that hot) on a previous summer trip.

I normally recharge the AC myself every 2 years, however, its never a perfect solution. When it gets really hot out, pressures in the AC system goes up.

Aqua Puttana
05-15-2015, 01:40 PM
Don't discount that a squeal noise could be a broken exhaust header bolt. I've learned that depending upon which stud(s) is broken the squeal noise can range from a quick whistle on acceleration to a fairly constant squeal through a range of engine speed/exhaust pressure.

The squeal noise is caused by the steel header gasket vibrating/moving within the loose header joint. Sort of like a musical instrument reed or one of those old time flat fabric mouth squeal whistles. That is what makes it dependent upon the exhaust header pressures.

The broken studs are sometimes hard to find. A flashlight at night to look for exhaust soot or trying a 12 mm wrench to tension each stud is often needed to track it down.

A quick chirp upon shutdown is often an indication of a bad alternator free wheel clutch pulley.

vic

rob99rt
05-15-2015, 04:59 PM
In my experience, the front AC really only does a good job of cooling the front seat area.

Did someone recently recharge your AC? If its overcharged, the belt can slip and you'll get squealing/chirping noises from the drive belt when running the AC. You can vent off some of the coolant and see if that helps. I had this problem when I was in 100+ temps outside of Colorado (the areas I go to where I live don't get that hot) on a previous summer trip.

I normally recharge the AC myself every 2 years, however, its never a perfect solution. When it gets really hot out, pressures in the AC system goes up.

A/C was recharged about a year ago, and it's been run a lot since then without the chirping/squealing sound. The squealing is only a relatively recent thing to hit (maybe within the last few weeks). I haven't noticed whether it does it more on hot days (higher pressures in the system) vs cooler days... I'll have to check this if the bearings check out ok this weekend.

rob99rt
05-15-2015, 05:02 PM
Don't discount that a squeal noise could be a broken exhaust header bolt. I've learned that depending upon which stud(s) is broken the squeal noise can range from a quick whistle on acceleration to a fairly constant squeal through a range of engine speed/exhaust pressure.

The squeal noise is caused by the steel header gasket vibrating/moving within the loose header joint. Sort of like a musical instrument reed or one of those old time flat fabric mouth squeal whistles. That is what makes it dependent upon the exhaust header pressures.

The broken studs are sometimes hard to find. A flashlight at night to look for exhaust soot or trying a 12 mm wrench to tension each stud is often needed to track it down.

A quick chirp upon shutdown is often an indication of a bad alternator free wheel clutch pulley.

vic


I've not noticed any squealing upon acceleration/deceleration/shutdown, but only when the compressor is kicked on. Didn't think about the gasket making a whistling sound, though... interesting.

lindenengineering
05-16-2015, 12:59 PM
Questions-Sorry Questions!
Why did you change out the belt in the first place?
Was it due to chirping, a PM exercise or something else and then you had the chirp/screech sound when A/C engaged?

Why did you elect to use an aftermarket belt?
Are you aware that two lengths of belt are applicable to the T1N model?

How many miles are on your van and have you done or had done any PM or component replacement maintenance work on the other components making up the accessory drive off the crank pulley?
Dennis

rob99rt
05-17-2015, 11:20 AM
Questions-Sorry Questions!
Why did you change out the belt in the first place?
Was it due to chirping, a PM exercise or something else and then you had the chirp/screech sound when A/C engaged?

Why did you elect to use an aftermarket belt?
Are you aware that two lengths of belt are applicable to the T1N model?

How many miles are on your van and have you done or had done any PM or component replacement maintenance work on the other components making up the accessory drive off the crank pulley?
Dennis

Belt had about 40K on it and I'd read somewhere that those goodyear gatorback belts sometimes slipped with age. I'd hoped that was the issue, but since it's still happening every now and then with the new belt, that wasn't the problem.


No, I didn't know there were two belt lengths for the T1N Sprinters. There's plenty of tension on the tensioner with this belt, though, so it's definitely not "sloppy". The tensioner is probably about in the middle of its range, fwiw, with the new belt on it.

There is around 84K miles on the van. I haven't replaced any of the tensioner/idler puleys yet. I did have to replace the alternator last year since the one-way clutch wasn't working any longer.

I was hoping to get under the van yesterday to test the A/C compressor, but it rained off and on all day. Looks like it'll be the same today and I'm not getting wet when I'm already fighting a nasty cold.

lindenengineering
05-17-2015, 08:17 PM
Belt had about 40K on it and I'd read somewhere that those goodyear gatorback belts sometimes slipped with age. I'd hoped that was the issue, but since it's still happening every now and then with the new belt, that wasn't the problem.


No, I didn't know there were two belt lengths for the T1N Sprinters. There's plenty of tension on the tensioner with this belt, though, so it's definitely not "sloppy". The tensioner is probably about in the middle of its range, fwiw, with the new belt on it.

There is around 84K miles on the van. I haven't replaced any of the tensioner/idler puleys yet. I did have to replace the alternator last year since the one-way clutch wasn't working any longer.

I was hoping to get under the van yesterday to test the A/C compressor, but it rained off and on all day. Looks like it'll be the same today and I'm not getting wet when I'm already fighting a nasty cold.

A few comments.
The belt length is crucial and using the right belt for the vin # is recommended. I only install the genuine belt which is thicker than the Gates or Goodyear product. I believe the OE belt is a Continental
The tensioner of course will be getting towards of it useful life of target 100,000 miles. Its really not the position of the tensioner but rather the coiled spring inside which arrests the tendencies of the belt to whiplash under the sudden load caused by A/C clutch engagement. The inability of the tensioner to arrest the whiplash is what causes the chirp. In fact with a strobe timing light connected to the coil wire of a gasoline engine you can in fact see the belt doing its thing!

Wear on pulley support bearings run out and pulleys including the A/C by themselves can often be the cause.
Of course I have to ask do you know what the refrigerant charge is?
Also head pressure might be getting a bit too high caused by a dirty condenser or radiator!
All items to take into account when running down a chirp complaint.
Dennis