Can not think of a better word to describe this. The cars runs just fine, except for no 3rd gear or overdrive, so am not driving it until I can find the funds for a tranny rebuild. So in the meantime I will worry about this problem. Starting last winter, at shutdown there is what sounds like a loud sucking sound coming from the engine compartment. Kind of like what lifting the lid off of a large can of beer would sound like. Does not seem to affect perfomance in anyway, but kind of annoying anyway. I did remove the air silencer years ago, but this sound is fairly new.