96 S500 Idler Pulley/Smog Pump

starky · 04-06-2012, 05:28 PM

I've been having a "high pitch" sound coming from my vehicle. For such a long time I thought it was my tranny because the sound is "synchronized" with every gear shifting. It also synchronizes with the engine like it's all "one" entity. So when I accelerate the "whinny" (not squeaky) sound gets higher. It's totally in synch with the engines every move speeding up & slowing down. So I took it to "Mr. Transmission" and they drove tested it and said the tranny is fine, has 190K on it. Had to believe them because what transmission place turns down $$$$. So after being perplexed I took it to another transmission shop and told him my complaint. I started car and he noticed the sound immediately. He put the "stethescope" on both side of engine while I pushed on gas pedal and said the high pitch sound is coming from my idler pulley area. Said it was so high with the scope on, he had to remove it from his ears In my opinion it sounds like a "bearing" is worn and not the pulley. I replaced serpentine belt about 500 miles ago and all the pulleys were tight. note: the sound was present even when I changed the belt but just didn't know what it was because I was just stuck on it being the tranny.

QUESTION: Should I just replace the pulley OR should I replace the entire Air/Smog pump with clutch & pulley? Would hate to replace pulley only to find out the "entire" assembly needs to be done. Any feedback from my Mercedes Benz family is appreciated!!

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oldsinner111 · 04-07-2012, 06:59 AM

maybe this will help I had to replace pulley at 150,000 miles

starky · 04-07-2012, 01:54 PM

Hey, thanks for the reply. However, didn't see any information attached except "1999 S 320 nitrous, 300sd not stock" in the reply section? oh...and that you changed yours at 150k miles. Outside of that i didn't see any additional information. Can you resend? or elaborate? Thanks

oldsinner111 · 04-07-2012, 03:37 PM

the pullys are a maintenace item to be replaced

starky · 04-07-2012, 10:41 PM

So based upon my description of the sound etc.....you think I should replace the "pulley" ONLY or the ENITIRE smog pulley air pump component which consist of pulley? What do you think? Just wondering got a guy parting out another 90 S500 what will sale me entire pump for $150 if I pull it. He's got 78k miles on his. Let me know what you think? Thanks

04-07-2012, 06:59 AM	#2
oldsinner111 Senior Member 1999 Mercedes-Benz S-Class Join Date: Jun 2010 Location: tennessee Posts: 495 Drives: s320 and 300sd	maybe this will help I had to replace pulley at 150,000 miles __________________ 1999 S320 plus 125 nitrous shot hp,modified grille area,and cold air intake,wrapped exhaust manifold,wrapped air duct,cold air,ceramic pads,no cats Borla exhaust one muffler14.4 1/4 mile 1983 300 SD not stock Mobil One ATF diesel rated oil both cars The Runaway Files by Tennessee Nate

04-07-2012, 03:37 PM	#4
oldsinner111 Senior Member 1999 Mercedes-Benz S-Class Join Date: Jun 2010 Location: tennessee Posts: 495 Drives: s320 and 300sd	the pullys are a maintenace item to be replaced __________________ 1999 S320 plus 125 nitrous shot hp,modified grille area,and cold air intake,wrapped exhaust manifold,wrapped air duct,cold air,ceramic pads,no cats Borla exhaust one muffler14.4 1/4 mile 1983 300 SD not stock Mobil One ATF diesel rated oil both cars The Runaway Files by Tennessee Nate

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04-07-2012, 01:54 PM	#3
starky Junior Member Garage is empty, add now Join Date: Oct 2011 Posts: 20 Drives: 96 S500	Hey, thanks for the reply. However, didn't see any information attached except "1999 S 320 nitrous, 300sd not stock" in the reply section? oh...and that you changed yours at 150k miles. Outside of that i didn't see any additional information. Can you resend? or elaborate? Thanks

04-07-2012, 10:41 PM	#5
starky Junior Member Garage is empty, add now Join Date: Oct 2011 Posts: 20 Drives: 96 S500	So based upon my description of the sound etc.....you think I should replace the "pulley" ONLY or the ENITIRE smog pulley air pump component which consist of pulley? What do you think? Just wondering got a guy parting out another 90 S500 what will sale me entire pump for $150 if I pull it. He's got 78k miles on his. Let me know what you think? Thanks

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