lawrence101

For the last few months i've bin sometimes hearing a laud high pitched squealling sound coming from the engine. This happens maybe once or twice a month and only last for maybe 5 to 10 second and goes away. it happens mosty at idle but it has happened once when i was driving at low speed. any ideas ?

CygnarManiac

First place i would check would be the universal (serpentine) belt, especially if the noise is happening on cool damp mornings.
SAFETY FIRST - MAKE SURE YOU OBSERVE THE SPINNING BELT, PULLEYS, FAN, ETC AND KEEP ALL CLOTHING, TOOLS AND BODY PARTS WELL CLEAR. If you aren't comfortable doing this then take the vehicle to the shop and have a trained tech do it!

Easiest way to test is to take a spray bottle and with the engine running spray some water on the inside of the belt. If the noise goes away then its likely a worn belt or possibly a pulley misalignment issue. If the noise gets louder it is likely a belt tensioner issue. While the engine is running you can also look at the belt to make sure its not moving back and forth or 'wobbling' on a pulley as the engine runs as well.

Another easy DIY check is to turn the engine off and using a belt tensioner tool or ratchet (usually 3/8" iirc) to loosen the belt tension and remove the serpentine belt completely. Its best to make sure that you have a sticker showing the belt routing or make a diagram yourself PRIOR to pulling the belt off. You can then try to spin any of the freewheeling pulleys (guide pulleys) to make sure that they spin freely and easily.

If you do a you-tube search on "diagnose fan belt noise with water" it should pull up a number of videos to take a look at. I found this one As always, the info you find on youtube is going to be slightly contradictory and likely aimed at selling you something. This one is for a company that makes a laser alignment checking tool. If the squirt test makes the noise go away temporarily then replacing the belt is a good first step, and you can check the relative alignment of pulleys with a steel ruler or straight edge while changing it.

lawrence101

Thank you for replying. I was thinking the same thing that it was maybe a belt issue or a pulley on the water pump , alternator or possibly the tensioner itself. It only happens sometimes and only lasts about 5 or 10 seconds and goes away so its hard to find where it is coming from. What i'm mostly concerned about is the transmission, had to get the leaking transmission lines replaced a few months ago, beginning to worry that it might be linked to that ?

lawrence101

I think i now know where the intermittent noise was coming from, the A/C stopped working a coupla months ago and since then i haven't heard anymore noise. I watched a utube video where a guy was changing out a faulty A/C pump and he mentioned that he was hearing a squealing noise when he turned on the air conditioning switch. Only thing is mine made this intermittent noise even if the switch was off. With the engine running, I did a quick test to see if the pump was spinning when the switch was turned on and it appeared to turn very slowly or sometimes it just stopped moving all together , very random and intermittent. We don't need air conditioning for much of the year here in Canada but its another one of those pesky things you'd like to have working on your truck. Oh well another chore to add to my to-do list this year.

[F2C]MaDMaXX

Don't forget that if you're in auto and/or in certain vent positions, the AC will turn on anyway and give no indication it's active.

lawrence101

Really ? Well that explains it, i know next to nothing about the AC system so thanks for that.
Oh and i found the utube video where it talks about the laud squealing noise coming from the AC compressor clutch assembly.

[F2C]MaDMaXX

Yup, so auto will essentially run AC all the time.

Vent modes that also engage AC: Windshield - Windshield/feet - MaxAC (duh!)