I'm Stumped...squealing Belt Noise

[stickman007 309]

Hi guys,A few days back, I posted on a thread thinking that my turbo is dying or I'm leaking boost. Turns out, the noise is from my alternator belt, (even though I was sure it wasn't a belt noise - failed). The reason for that rookie mistake was because I just replaced the belt not even a month ago...I went under the car today to found out that the belt I put in was completely worn! There were ridges on each of the ribs with signs of glazing. I pulled my spare belt out and replaced it (made sure it was properly tensioned), and thought I've solved the problem once and for all...failed again. The noise came back not even 2km down the road! I went took everything apart and checked, the tension is still good!I'm stumped and not sure where to begin...as far as my experiences serve me, aux belts squealing are rpm dependent and not load1) the car doesn't squeal without load - why?2) lower pulley is not bent or out of alignment3) alternator pulley looks pretty shiny (worn?)4) the sound appeared about a week ago, developed louder and more frequent on my trip out to AB - its really annoying nowCan anybody shed some wisdom?My next move is to swap the alternator pulley from my project smart and see if there's a difference.Or am I just confused and it's an intake/exhaust leak that sounds like a belt??!!Or just going crazy and hearing things?Help..Izzy

Edited May 11, 2013 by stickman007

[CANMAN 23]

Did you spin the Alternator pulley?There was a post recently about the Alternator bearings seizing on a members car.Check the water pump and idler pulleys as well.Canman

[stickman007 309]

Both alternator and water pump spins freely without noise or play...

[CANMAN 23]

Izzy,If you have a spare Alternator swap it out, could be the bearings in the Alternator going.Check the idler pulley as well.Canman

[stickman007 309]

Izzy,If you have a spare Alternator swap it out, could be the bearings in the Alternator going.Check the idler pulley as well.Canman

I idler already checked I think i'm going to run without belts first to determine if its even a belt issue...driving the car 30sec without water pump shouldn't hurt too bad, i don't think. Still not sure how the load has anything connected with the belts...Izzy

[Alex 21]

Pulleys do wear, and will cause a new, correctly tensioned belt to slip. A low-mounted belt at the rear of a car driven where there is a lot of sand and dust accelerated that wear.Inspect the new belt, the old belt and the pulley. There should be no contact at the tops of the pulley ribs/bottom of the belt ribs. All the contact should be on the sides of the ribs. A shiny tip of the pulley groove indicates contact. As the belt enters the groove it fits snugly into the groove, then as it starts to bend to the pulley circumference the belt ribs bulge out, firmly gripping the pulley. This is the intent of any vee-belt design, so the belt even under high load doesn't have to wedge itself deeper with relative motion between the belt and pulley and subsequent wear. The belt is already gripping the pulley under only the static tension before the load is applied. If the pulley grooves are worn the belt will ride on the top of the ribs (most poly-vee belts) or the bottom of the groove (single Vee belts) and can't grip properly. (BTW, pulleys often have different groove geometry depending on the diameter so the belt can function properly without excessive wear.)I think it's your pulley.

Edited May 6, 2013 by Alex

[MikeT 744]

I had a well and truly polished pulley on the old green car due to me ignoring slippage for some months but a properly tensioned new belt banished that. When tensioning the belt, make sure the pivot point for the bracket is truly clear of grit; otherwise the torque figure will not be correct. To clean mine out, I drenched the pivot area in WD 40 and all kinds of crud blew out.

[stickman007 309]

Thanks for the advice...will order a new pulley/swap alternator asap. Will post results

[tolsen 630]

You should always check tension by measuring. Use a krikit tester or measure belt vibration frequency. There is a thread on this forum with details how to do it. Alternatively check tension with a guitar. Longest span aux belt vibration frequency on a new belt should be 230 Hz, just below A♯3/B♭3 and above A3.

[stickman007 309]

What do you know!! I'll let the picture speak for itself:I pulled the one off my project smart...what a PITA to get the alternator out!I just swapped the pulley because I didn't have time to remove the alternator from my cabrio.Noise is still there though...maybe the belt that I put on yesterday is glazed now? (didn't inspect, the sun was setting fast)Will check the belt's tightness tomorrow again to make sure I didn't mess up...but if the noise is still around, I will swap alternator this weekend

[MikeT 744]

It looks as though that pulley was made by the same supplier that made some of the oil pump sprockets

[stickman007 309]

Rechecked my belt this morning...still making noise, more high pitched now...still stumped

[cruise_carter 1]

looking at the pulley picture, one is worn down pretty goodmy thought would be pulley is not spinning freely and the belt is wearing it down

[dieselkiki 7]

Hi Izzy, I had the same problem there are 2 years ago. It took me almost one year to find and resolve the problem. The source of this problem is the composition of the alternator pulley. The original alternator pulley are aluminium made. Aluminium is a soft metal easy to worn even if they coat it with an harder surface. Straps and pulley are very exposed to dust, rock, sand, salt etc... and after 3-4 strap lifetime, the pulley is wear out. Even if you put a new belt, it will still slip and making "kwicking" noise at cold idle speed and on load or when you drive on wet road. So I went to my good friends at mercedes-benz dealer to buy a new pulley but they said to me: "Hum, unfortunately for you sir, the pulley only come with the complete alternator assembly. So it's about 425$" HAHAHHAHHAH!!! FUNNY!!! Welllllll... I don't think that I will pay this amount of money for a bad engineered pulley material. Even more as this new alternator still get the same shitty aluminium pulley!So I searching everywhere to buy just a single pulley but no success. I ask to my brother to make me a steel one but that was a 250$ of material + labor to waste juste to built a new pulley. I finally talk about my pulley problem with the guy in the machine shop I know where they rebuilt alternator and startor. I show him my old pulley and he said: "I probably have a solution for you." When he'sback, he hold a very similar steel pulley in his hands. The pulley wasn't the same but the 5 V-grooves was the same and to match the right offset, he machined the shoulder and the inner side of the pulley. I bring it at home, instaled the pulley on my alternator and you know what Izzy? No more squealing noise at any weather and for a while as I think. The steel is harder to worn out than soft aluminium. My steel pulley is on my car from one year now and I'm enjoying a no noise pulley from this time and it cost me about 43$ for this pulley.So I hope that my pulley adventure will help you guy!Have a good day!Dom

Edited May 8, 2013 by dieselkiki

[bilgladstone 13]

Probably the same thing, though to a lesser degree, is happening to my pulley. After replacing the belts, I still hear a very light whirring. Possibly due also to leaving a deteriorated belt on the car too long that wore the grooves. I thought the noise this winter was a slightly corroded alternator stator/rotor. Nope. Shredded belts :(I like Dom's solution :thumbup:Bil

[stickman007 309]

The noise is getting worst, especially when load is over 40 on scangaugeI'm going to swap both the alternator and crank pulley tonite...if this still doesn't work, then I have no idea.Dom: lucky for me I have an alternator/starter guy here at the puddle. I gave him the worn pulley and he said that he can order me on (I think one of the ford 5 groove ones is a direct match)...is the crank pulley steel or aluminium? I bet that's an expensive part to replace.If I keep stealing parts from my project, I might as well turn it into a parts car, cuz buying new parts to fix it wouldn't be worth it!Thanks for the replies guys!Izzy

[bilgladstone 13]

Is the Ford pulley made of steel? If it is, and if it IS a direct fit, that would be elegant!Bil

[Alex 21]

Four separate thoughts on this topic:The belt is a standard PK series micro-vee, size 5PK768. The actual belt number (not the MB part number) should contain something like 5PK768 inside a longer string. "5" is number of ribs, "PK" is the rib size, "768" is the length, the rest is construction, manufacturers internal info, etc. Any 5 rib PK pulley of correct diameter and bore size will fit. The crank pulley, being much larger in diameter, won't wear as fast and even when worn won't slip as easily.The water pump is on that belt as well, nothing says it is the alternator slipping.I still don't get how increasing engine load could affect belt slippage, though, could be something else mimicking belt noise.

[dieselkiki 7]

Dom: lucky for me I have an alternator/starter guy here at the puddle. I gave him the worn pulley and he said that he can order me on (I think one of the ford 5 groove ones is a direct match)...is the crank pulley steel or aluminium? I bet that's an expensive part to replace.Izzy

The crankshaft damper pulley are steel made and W/P too. If I remember well, the pulley that I bought was a ford one. They just have to removed some 1/16" to the shoulder and 5/16" where the nut screwed just to get enough tread.Alex: The load grow proportionaly to RPM. As exemple, the alternator is harder to rotate at high speed than idle speed. It produce always +/- 14V but at high RPM, the alternator push more ampere and need more power from engine to rotate faster. So, it's could be the reason why when the engine rev more, the load is more too and the sleeping occure.

[Alex 21]

Stickman said LOD, a scanguage readout that is the percentage of available power the engine is producing, so not RPM correlated. Also the torque on the alternator pulley won't increase with RPM. In fact if you look at an alternator output curve it ramps up very quickly at low speeds, then levels off, so the torque must decrease with a speed increase. Power of course is torque and speed combined, but you know this already, you just didn't think it through or got caught up in language. No offence, I know your english is far better than my french!Stickman: That's correct, right? Noise is engine load related, not RPM? More detail the better!

Edited May 8, 2013 by Alex

[stickman007 309]

Will do test run tonite...hopefully without the belts to settle the belts or not question.The noise is definitely load dependent because once the throttle is off, doesn't matter what rpm, it will quiet down.I've read somewhere today that belt type noises can be mimic by a leaking exhaust manifold? (UK site - guy claims that he had a broken exhaust stud)I'm finding more questions than answers - being an ex-HD mechanic, I feel ashamed that I can't even tell the noise apart :(Izzy

[stickman007 309]

Forgot that I left my torx sockets at my buddy's place Can't work on the car till Friday...On the up side, get to pull out my motorcycle for some nice weather riding

[stickman007 309]

Noise problem SOLVED! - I thinkI removed the belts today and inspected with better lighting.So after a week of squealing, I removed all the parts and inspect:1) noticed that the sidewall of the belt is worn - misalignment? (rookie mistake?)2) no wear in the middle of the grooves - pulleys are okay at this point, the slip could be from the water pump?3) water pump has a leak! (didn't noticed that earlier in poor lighting)4) water pump pulley rotates smoothy, but with a bit of resistance - water pump is the only pulley that can be affected by load?Conclusion - water pump is worn, as the load increased the pump has enough resistance to slacken the belt (only during higher rpm) causing the squealing, (not enough during idling).I slap everything back together, still squeals, no surprise...What do you guys think?Anybody know the cheapest place to purchase a water pump?Izzy

[tolsen 630]

I think insufficient belt pretension. Water pump will be ok if there is no significant play in its bearings. What frequency or note does longest span vibrate at when you twang belt?

[bilgladstone 13]

Isn't the water pump designed to drip a tiny bit through a weep hole when the impeller seals start to get a bit worn, as an early warning sign of wear quite prior to failure? I seem to remember reading that somewhere...Bil