2001 protege engine hissing noise.
 

Had a minor hissing sound comming from the engine, somewhere between the battery and air filter pannel, around that area, cannot pinpoint it. Air filter is fine. Had car in to get the block heater installed and cooolant fluid topped up.

After I picked the car up found that the hissing sound is a bit louder, still comming from the same place. car idles fine so far, engine temp is normal, no problems with speed or acceleration, all fluid levels are fine.
Anyone knows where it could be comming from? Is it normal?

2001 Protege 1.6L 103HP, 44700KHM.
All new fluids.

IF its not a leak in your stock piping , it sounds like what i have, its probably coming from inside your Intake Manifold.

Does the sound go away if you give it accellerating gas and come back at a constant RPM. anyways if its that, its probably nothing , could even be just Carbon buildup in the manifold causing a odd hiss sound.

if it starts getting louder, seriously think about going to the dealer, but it will be costly if they rip it apart and look inside.

If its not that, the no clue what it could be

But if you get a COLD AIR INTAKE, it makes your car sound real mean lol haha

THX for the reply,

The Sound is constant, can only hear it when Im outside of the car, more when the hood is up. Can't hear squat inside the car. Dunno why suddenly it got louder after the car got a block heater installed. Unless they hit nudged something out of position when they were runnig the block heater power cord through. Wish there was some way of finding out instead of going to the dealer.

Yeah, I was going to mention the CAI. Guess that's not the problem. & I don't have any experience w/block heaters. I know when I shut my car down I hear the intake pressurizing & you can hear the psssst. I have a short ram though.

hahah you gusy should hear my car, at the TOprotegeclub in toronto everyone can hear my car coming lol, aka "viper" the hiss is massive

Are you turbo'd & that sound comes from your bov? Or, is your intake doing that!?

think of a turbo blow off sound , but always on, thats how loud it is, it sounds kinda cool, it goes away when you give it gas and when you let off it comes back. it also is there when i am leveling off at a constant RPM.

Had it inspected for free at Mazda those guys are really nice and do alot of work for me, all i do is bring them donuts lol and we have alot of garage bay area talk.

The sound is coming inside the engine, just beyond the Throttle body,
their guess is that it could be carbon deposits slightly obstructing flow. We did a dyno pull after the CAI and we actually gained alot more then my friends AEM,

I think it may have something to do with the sound but not sure, even when we took the CAI off and went back to stock the sound is still there.

the CAI just extends the sound to the tip of the pipe.

sounds bloody cool.

By the way whats the BOV?

You just about said it in your post above,
BOV = Blow Off Valve..or pop off valve..

Same thing for me, I shut the car off and hear the "psssst" takes a few seconds for it to go away. Had the mech at Crappy tire check the air intake, sound is a tad quieter now when he opened and reclosed the air filter compartment, said the sound was normal, found no leaks.

Check the power brake master cylinder. Sounds like a vacuum leak. Spray carb cleaner or WD40 around it/hose connection to hear if the hiss suddenly stops...

The Mech opened up the air filter container and we found that the sound was coming from the air intake where the air filter is inside the main intake after the air filter, but when he closed the air filter cover the sound was muted, and no holes or loose connections were found on the main intake pipe. So doubting a vacuum leak. Car runs the same as always.

in my case, Mazda confirmed the sound was engine internal, changing the intake had no effect. :(

so long as the sound doesnt change, you should be fine.

worry if it gets louder