Hissing sound...?

[dandigiacomo]

Hey guys, I'm driving a 1984 - 318i (5 spd),... It's got 230k on it and everything is original. It runs great considering its age and mileage. I'll be asking allot of questions on here because I'm 16, its my first car, and I'm sure no mechanic. I bought a Bentley shop manual and I read it like a Bible, but it doenst have a faq / trouble shooting section.

THE QUESTION: When accelerating in lower gears (1st, or 2nd), and *sometimes* while idling I hear a slight hissing sound coming from the engine compartment. Sometimes a higher pitched hiss. Its just for a few seconds, then its gone... then it'll come back, then leave,... and so on. Once the engine is warm and running I hardly notice it. (That may be because the engine sound drowned out the hissing... I dunno.) I never over-heat, and everything still runs right. What could this be? I just don't want to screw up my engine. I'd appreciate all the help I could get. THANKS!

 

[Bimmerlife]

Most important thing to change on the E30 is the Timing Belt. You should do that soon if you dont know when was the last time they changed it. And also the rest of the belts. Thats what could cause that sound you are talking about.

By the way

 

[dandigiacomo]

Hey Bimmerlife,... I'm assuming I should go to a dealer. OR at least a shop for this. I don't have a clue what I'd be getting into. On an OEM parts site I saw that a timing chain that is specified for my car is approx $30. So it wouldn't be that big of a deal. Just labor... No telling how high that'll run me. Thanks again... and keep the suggestions coming everyone!

 

[epj3]

I'm pretty sure it's your idle control valve.

It's this thing (i overlayed it in orange with a red arrow pointed to it...)

If i turn the key to the on position, but do not start the engine, I can hear it whine (i believe it's a motor that controls the flow of air.)

 

[epj3]

Oh yea, check to make sure your AC clutch is releasing.

 

[jrt67ss350]

His idle control valve probably isn't in the same place - he has a 318i. As far as I know, you don't need to change the timing chain on the 318 as a regular maintenance procedure (yes, 318's have chains, not belts). The six cylinder 325 has a belt that must be changed at least every 60,000 miles. If you are hearing the hissing when accelerating, then I doubt it's the idle air control valve, since you aren't using it when accelerating.

 

[dandigiacomo]

Yeah, I noticed that my engine looks way different than the one epj3 pictured. But I appreciate the help. I don't think its the chain, it doenst sound like a belt or chain issue. I dunno... I'd like to look into the AC clutch... Whats up with that? Why would it hiss if it were engaged? My AC doens't work properly... I figured it was the compressor that was acting up. Is this related? THANKS AGAIN

 

[epj3]

True, good point jrt67.

Ac usually makes a hissing sound (if you could hear it over the engine and compressor) when it runs.

 

[dandigiacomo]

So you guys are saying that if my AC is on, I may hear a hissing noise? And its real quiet, that could explain why I only hear it when my RPM's are way low. I don't know about this tho... My AC switch doesn't work right and some of my climate indicators don't work right. So I actualy don't know if my AC is on or not. (See, the compressor doenst make the air cold enough to tell if its actualy on or not.. Yes, I can run the blower, but I dont know if the AC is 'engaged'). I dunno, I'll figure it out. THANKS and if you have any idea's let me know!

 

[epj3]

Well, it does sound suspicious... I honestly think I can hear a hiss when my AC is on...

 

[xLibelle]

does it happen when you are moving? could be your brakes dragging.

 

[Big Daddy]

318's have timing chains and they should last the life of the motor. they also rattle slightly when cold, but the rattle should go away when warmed up. If it continues to rattle after warming you may need a chain rail, tensioner or chain. Hissing would not be the chain!

 

[dandigiacomo]

Nope, not breaks, just replaced them all around and its not when iI'm moving... its just a slght hiss from the engine compartment. My chain doenst rattle, not that I know of. All that looks pretty good. I'll figure it out. I guess... lol