Hey there!

I have begun noticing what is either a "chirp" or a "squeal" under the hood of the GL upon cold start. Right now the sound is subtle and short-lived. I vaguely recall that chirps are more bearing related and squeals are more likely belt related. I sprayed a little water on the ribbed side of the belt while running and is squealed a good deal, but to me this is logical and may--or may not--really identify the issue as belt related. A little guidance on this spray test approach would be appreciated. Any tricks from the pros to determine pulley vs. belt noises?

I have an auto stethoscope on order and it should arrive in the next week or so and am hopeful that it will give me more insight. Looking at the repair history of the GL, I see no notes indicated that the belt, pulleys, or idle tensioner have ever been replaced. I'm pushing 90k right now. In researching the parts necessary to do whatever comes next, I noticed a couple drive belt kits that include a belt, 2 pulleys and a tensioner. My question for you all is whether you believe there would be any value at this mileage to just do all these pieces as opposed to just the one that may currently be the problem? Other than the slightly tight space for the work, it doesn't seem too complex. In addition to your thoughts on whether it makes sense to do all these pieces now, I would appreciate any insight you have as to whether or not this is a reasonable job to DIY?

Thanks in advance!

 

i just replace the Idler Pulley and Belt on my Brothers GL450.. his was Squealing for a while and then the Pulley Seized and the belt broke..

 

Try squirting the water directly at one pulley at a time - trying to get the water into the bearings. Haven't done anything with my pulley's, yet, but there may be a little plastic faceplate/cover snapped on it. From my experience, the first culprits to go are the idler or tensioner pulleys. Depending on cost and how much time you anticipate it taking, determines if you want to do more than just the offending pulley. If you were paying someone to do it... sure, doing them all. But if you're doing it, then it's just a matter of your perspective on your time/labor. I have usually just replaced as needed.

 

So I wasn't able to actually get water into the bearings of the pulleys. My spray bottle apparently can't overcome the breeze from the fan blade ;-)

However, when I hit the ribbed side of the belt with water the sound increased in volume and duration. Based on my recollection and research, this would seem to indicate a tension problem most likely. The auto stethoscope is supposed to arrive today and I may get a shot to listen before heading out on another college visit with the youngest. If my logic flows, my plan is to replace the tensioner and belt. Thoughts?

 

Belts glaze then chirp with age/miles.

How old is your belt? If in the 40k miles or so range, change it. It is an easy DIY or relatively inexpensive at an independent mech. It is NOT something you have to go to a dealer for. Cheap insurance. I had a belt let go on my 2008 E320 and it took the harmonic balancer and power steering pump with it as well as stranding my wife. Total cost $1900 at the dealership not counting the tow which was covered by AAA.

 

I see no record in My Carfax account (which is very comprehensive overall) of a belt being changed along the way. I am pushing 90k right now. The mileage, and the security, are why I was planning to replace the tensioner and the belt. If I get a good look at the belt and it appears glazed or pilled, I may just do the belt.

 

At 90k miles, please just do it. Tensioner may not need to be replaced.

 

FYI... Poke a hole in the top of a water bottle - allows for a bigger stream. But...

It sure seems that since the only thing you are bascially messing with is the belt, and the sound changes (doesn't matter if it goes away or gets louder, the main point is it changed), that the belt is the issue. I forgot to mention this above, but from my experience, a quick chirp is a belt issue, while a longer lasting squeal is a pulley bearing. The chirp may go on for a period of time, but it has more of a very distintictive "on/off" pattern.

If you call or, better yet, stop by a Merc dealer with your VIN, they can look up service history. Of course, that will only tell you service that has been done at the dealer. But it may give you more info - and you ask them to print it out for you.

If I was in your shoes, with the info you have at this time, I would probably do the belt and the tensioner. At a bare minimum, I would chalk it up to good PM and "starting fresh".

 

That's the plan for the weekend...knock out the belt and see where things go from there.

BTW...clever use of a water bottle ;-)

 

if you taking the belt off you might as well replace both idler Grooved & Smooth they are fairly cheap

 

I changed out all of the idlers and tensioner/idler pulleys as well as the serpentine belt around 95k. You will have peace of mind and you are already at that point so it is no big deal to change them all.

As the vehicle gets older i have found it prudent to replace items that work together as a system to keep the reliability up if you are shooting for high miles. I am trying to go to 300k with mine, at 126k now and replaced a good wave of parts since 50k including all suspension with compressor at 104k.