Occasional noise when heat is turned on

[Classy Comanche]

Hey guys so this is one of those things that has started happening out of the blue. When I turn my heat on. Low, mid or high I will occasionally get squeaking noises that cease. It'll do it sometime later and cease again. I can't pinpoint it because it mainly does it when driving. I'm about 99.99% sure it's not the serpentine belt because it doesn't squeal when doing a cold start and its like 2 months old. I don't really know since I drove to work this morning scratching my head. Heat blows nice and hot. Make you sweat if you ain't careful. I didn't know if you guys had a idea or had this happen? Thanks!

[fiatslug87]

Maybe the blower motor. Put a long screw driver on it and the handle to your ear (or a mechanic’s stethoscope if you have one) and listen for the noise. It’s under the expansion tank.

[Classy Comanche]

I'll have to do that on one of my days off. I did crank it up, put the heat on mid and let it idle in park and I was giving it gas and as I gave it gas 2 out of the 14 times I feathered it it would begin to squeal and stop or I would be going up rpms about 1100-1200 and it would squeal for half a second then quit. Definitely not saying it's not the blower motor but that is my observation. Tomorrow morning I'll drive to work with no heat, and be freezing admittedly. But for science! I'll see if it does it then. 

[Minuit]

Check for oily residue on the serpentine belt. You may also want to check or have checked the belt tension.

 

Is your AC operational? Throughout my MJ ownership, that's been the one consistent source of belt squeals - the refrigerant oil leaks through the front compressor seal onto the belt and pulleys.

[Classy Comanche]

So I can confirm 100% with no doubt in my mind that there is no squeak when the heat is off. It's quiet as can be. When I got to close to work I turned the heat on low and it squeaked for roughly 2 seconds and quit. I turned the heat up and it was quiet for a while. Then it started doing it again. So when it started again I immediately turned the heat off and when I did the squeak immediately stopped. My AC does work to my knowledge. I had it recharged this summer. So it specifically squeaks when the heat is on. I don't think it's my blower motor because it's not a high pitched whirr like a constant wheeze sound. This almost sounds like every full rotation of the engine it squeaks then does eventually stop. Heat blows hot and good. This here does have me scratching my head. I'll take a peek and see if there's oily residue on my belt and such. I'll also have the mechanic take a look at my tensioner when I go back for a personal inspection soon.

[Minuit]

Record the noise.

[cruiser54]

Tighten the belt. 

[PIKE]

 

 

https://www.gates.com/gb/en/power-transmission/power-transmission-tools-and-merchandisers/power-transmission-tools.p.7401-000000-000003.v.7401-00072.html

 

[scguy]

Unplug your compressor and try it with the heat on again. 

[Classy Comanche]

I'll record the noise best I can when I can. I'll mess with it and check around as you guys suggested. I also need to take it by the shop for a new exhaust anyway so I'll have them check the compressor and such

[cruiser54]

Tighten the belt. 

[Minuit]

Tighten the belt.

 

If noise persists, record noise and seek further counsel.

[cruiser54]

THIS^^^^^^^^

[Classy Comanche]

I've been trying to get it on video but when I fumble for my phone while driving it stops or it'll do it for a split second and stop. It's a very high pitched squeak sound. Definitely does it when it makes a full engine rotation. I'll have it tightened up and go from there. The belt is new after all. Once again this morning it did it and no I couldn't catch it on video because I fumbled for my phone and fell in the floorboard. Great. So I did just turn the heat off and once again immediately stopped. But this go around I'll have said camera ready so all I have to do is press record 

[cruiser54]

Tighten the belt. 

[jpnjake]

On 12/17/2022 at 8:38 AM, cruiser54 said:

Tighten the belt. 

 

On 12/17/2022 at 9:18 AM, PIKE said:

 

 

https://www.gates.com/gb/en/power-transmission/power-transmission-tools-and-merchandisers/power-transmission-tools.p.7401-000000-000003.v.7401-00072.html

 

 

On 12/20/2022 at 7:23 AM, cruiser54 said:

Tighten the belt. 

 

On 12/20/2022 at 7:58 AM, Minuit said:

Tighten the belt.

 

If noise persists, record noise and seek further counsel.

 

On 12/20/2022 at 8:47 AM, cruiser54 said:

THIS^^^^^^^^

 

43 minutes ago, cruiser54 said:

Tighten the belt. 

Tighten the belt. I can’t believe nobody suggested this yet 

[Classy Comanche]

Lol yes I'll certainly tighten the belt. I do believe that is the reason it's doing what it is doing as so you guys, and thank you! However. I did manage to capture the sound on my way home. I was driving, phone was positioned right above my radio. It was also raining and I had the wipers on. So I do apologize for those sounds but I did capture the squeaking sound! It sounds like baby birds. The heat was on the setting max and the level was low.

[cruiser54]

Tighten the belt.

[Classy Comanche]

I am. I was just showing the high pitched squeak I've been talking about and missing for you fellas to listen to. I thank yall! I'll have it all tightened up in no time! 

[AZJeff]

The 4.0 in the MJ and XJ models is VERY sensitive to lack of proper belt tension.  On top of this, they seem to need a hellacious amount of tension compared to some other vehicles.    This means that many DIY guys under-tighten the belt, and noise ensues.

 

Add in belt aging, and crud on the belt and/or pulleys, and it can be really annoying.

[cruiser54]

I wish someone had mentioned belt tension earlier on. 

[fiatslug87]

I think the belt is too tight.

[jpnjake]

2 hours ago, cruiser54 said:

I wish someone had mentioned belt tension earlier on. 

Someone should’ve really thought of that  maybe next time someone can suggest it 

[Manche757]

Don't forget to loosen your belt when you sit down for Christmas dinner.

[Minuit]

16 hours ago, AZJeff said:

The 4.0 in the MJ and XJ models is VERY sensitive to lack of proper belt tension.  On top of this, they seem to need a hellacious amount of tension compared to some other vehicles.    This means that many DIY guys under-tighten the belt, and noise ensues.

 

Add in belt aging, and crud on the belt and/or pulleys, and it can be really annoying.

I know we're joking around a little bit here, but Add in the janky manual tensioner setup that is somewhat prone to being damaged, and it can be annoying to get right.