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MB W211 E200 CDI 2006 Strange noise

1282 Views 1 Reply 2 Participants Last post by  PSDCamperVan
Hello! I got some strange noise when i start up completely cold car. It starts in about 5 second after start up and goes about 5 seconds then it just stops for a few seconds and does it again, after a little while (5 times) it stops. My guess would be A/C compressor but not sure. Any suggestions?
Link to video (you can hear sound at first few seconds!) -
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Video sounds like something being driven by serpentine v-belt is chirping, maybe a tensioner but could be AC compressor too (mine just spun it's pulley bearing last week & had to be replaced $$ :/ ) I was getting a squeaky chirp sound from v-belt whenever engine shutoff that I just kinda took for granted because everything seemed to be working well & no DTCs were ever logged in any DAS diagnostic quick tests. The HVAC system had a slow freon leak that would require 300g recharge of R134A every 6 months or so to cool properly & looking at compressor, it always appeared to be oily & dirty but I ignored that since everything seemed to work well otherwise. I was suspecting either high or low pressure shrader valves for HVAC leak as this is only location I would ever see yellow dye w/ black light & yellow lens glasses during leak inspections. I now suspect it was probably compressor all along but time will tell. That chirp sound at shutdown no longer occurs with new compressor installed. I would remove v-belt & spin each pulley by hand to see how easily they each free-spin or if there is any in/out play in their alignments also listen for free-spinning sound of tensioner pulleys to see if any of their bearings are possibly starting to bind or catch, even slightly. Be sure to take a picture of v-belt's route to refer to when putting it back on if you do remove it. Is your A/C working properly? The temperature should be approx. 42F coming out of evaporator core in dash if so. Mine was working right up until pulley came loose & stopped driving compressor. The only subtle warning I got when it failed was presence of what I mistakenly believed to be coolant odor that turned out to be freon/PAG 46 oil vaporizing off hot compressor... that & v-belt developed a rhythmic thump that corresponded to engine RPM. I got sooo lucky that pulley didn't pop off before I was able to drive it to workshop which I did immediately upon discovery of rhythmic thump & observation of compressor pulley wobbling in & out from v-belt's track. Good luck & I hope it's NOT your AC compressor, cost me about $1500 to replace (dryer & v-belt replaced included in that figure also).
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