Help to diagnose whining from engine compartment
09-03-2018, 01:41 PM
#1
Junior Member
Thread Starter
Help to diagnose whining from engine compartment
Hello all,
I have a whining sound coming from my engine compartment, it sounds very much like a bad bearing or something. The pitch changes based on engine revs so I'm fairly confident that it's on the serpentine belt. Is there anything I can do to diagnose or narrow down where the sound is coming from, short of replacing things? it's hard to tell, but it seems to be coming from the middle part of the engine, near then secondary air pump up top. I don't think it's the alternator (lower left corner), but that's about as specifically as i can narrow it down by sound alone. I also tried removing the secondary air pump but that didn't help.
My next best guess is the water pump, but that's a pain to replace without knowing that's the problem.
2008 CLK350 w/ 90k miles
Thanks for your help!
I have a whining sound coming from my engine compartment, it sounds very much like a bad bearing or something. The pitch changes based on engine revs so I'm fairly confident that it's on the serpentine belt. Is there anything I can do to diagnose or narrow down where the sound is coming from, short of replacing things? it's hard to tell, but it seems to be coming from the middle part of the engine, near then secondary air pump up top. I don't think it's the alternator (lower left corner), but that's about as specifically as i can narrow it down by sound alone. I also tried removing the secondary air pump but that didn't help.
My next best guess is the water pump, but that's a pain to replace without knowing that's the problem.
2008 CLK350 w/ 90k miles
Thanks for your help!
09-04-2018, 12:12 AM
#2
MBworld Guru
Remove the belt and run the engine briefly to listen for the noise. If there's no noise without the belt, then check the idler and tensioner pulleys for bad bearings. If the noise persists without the belt, then get a mechanic's stethoscope to track it down.
09-10-2018, 10:39 AM
#3
Senior Member
Can put your head close and try to listen for the direction (is it a pulley on the left vs right). Then you can sometime figure it out by trying to move them side to side and look for any play. My water pump bearing is going and this is how I found it. Will be replacing it next weekend.
