mower420

92 SC400 with 155000 miles, for a long time now i've had a really loud rattle/vibration that only happens at idle when i'm stopped and in drive. if i tap the gas at all or put the car in neutral or park it goes away. it has never affected the performance of the engine, its just really annoying at stop lights. Anyway, i just found the location of the noise, it is the A/C compressor. if its making the noise i can pull on the compressor and the noise stops..so its some kind of vibration or bad bearing. my A/C hasn't worked for almost a year (perhaps the same time that this noise started). the compressor clutch doesn't engage and i've pushed on the tire like valve on the compressor and nothing comes out, so i'm assuming i have no freon. with the belt off, the a/c pulley spins freely and the clutch spins with a fair amount of resistance (not sure how much is normal) and the noise is gone with the engine running and belt off. i'm selling the car as soon as i get rid of this noise, so i'm not too concerned with the a/c working. i just need to fix this for as little money as possible. has this happened to anyone before? i'm not sure where to start, could it be a bearing inside the compressor? the compressor is not loose or anything, its just like at the certain frequency of low rpm and car in drive it makes this LOUD vibration. any help would be appreciated, i'm pretty good at working on engines but i'm not too familiar with A/C systems, i've searched the board and can't find anything on this. thanks, Lonny

Hello, for a few months now my 92 SC400 has had a horrible sounding vibration at idle (i just now have some money to try and fix it). The car runs great, and the rough idle doesnt effect anything but is pretty embarrassing at stop lights. here are the symptoms, i searched the boards and couldn't find anyone with the same problem. -it only makes noise when stopped and in drive, i usually shift into neutral at stop lights so it won't sound so bad (but sometimes i can still hear it a little bit in neutral) - the sound seems to be coming from the front of the engine, i want to say that its coming from around the belt tensioner assembly on the front -there are no problems with acceleration or rough idle, everything is fine except for the annoying noise. -the noise seems to sound "circular", like it gets louder then quieter, louder quieter, etc continuously (although sometimes it is just a constant loud buzzing vibration) -if i tap the gas pedal and get the rpms to anything above idle the sound goes away, and it never makes any noise any time other than idling. my first instinct is that it is the belt tensioner rubbing somehow, i probably will replace that for now since its an easy job and doesn't cost much. i've read some things about engine mounts having problems, but i dont know if these symptoms really point to that. anyone who has had similar problems or knows what this could be would be of tremendous help! thank you. -Lonny