Hello everyone, as you read from the title, I have a 1994 honda civic dx with a d15b7 5 speed manual. Recently I've been having an issue that is quite strange and I haven't been able to find any answers that fit my symptoms. For the record, my engine is completely stock internally, has Ebay headers and an intake. I recently discovered a weird sound from my engine bay while driving it. The closest thing I can relate it to is like someone airing out with air suspension or someone using an air gun. I'll be driving just fine then all of a sudden I get a sound of air quite loud from the bay and my exhaust gets quiet. The sound gets louder with any increase in rpm, however, I am not experiencing any noticeable power loss. The strange thing is, when I come to a stop and turn my A/C on, the sound goes away, but then returns while driving. I checked for vacuum leaks and I haven't found anything obvious, which the volume of this sound leads me to believe it would be a major leak. I must note that my clutch is going bad and I need a new clutch master cylinder along with a couple of other small things. A/C works perfectly fine and is ice cold always. Please if anyone here knows anything or can lead me in the right direction it would be much appreciated. I just need this engine to run for a little longer while I muster the parts for an ls swap. Thank you.

 

Closest thing I can think of off the top of my head might be the cooling/AC fan motor going out. They can get pretty darn noisy once they start going bad.
Try sitting around with the hood popped and watch it once it gets warmed up.
Thinking that because toggling AC affects it.
Regardless keep a close eye on your coolant lvls to!

Wish you luck.

 

My coolant levels stay steady and I have no overheating issues so I don't believe it's that. I'll check out the fan motor. It difficult to hear at idle really. It's only really noticeable when driving which is why I haven't been able to pinpoint the source. Thanks for the info. I'll update if I find anything there.