Vacuum leak (new to european cars)

[z28]

Just got my first e30 this week but I don't know much about e30s. I was taking a look under the hood of the car I noticed a vacuum leak, and it looks like its from the hose that goes from the back of the upper intake manifold to the intake boot. I was just wondering what the thing attached to the hose is. Here is a picture of what Im talking about, by the way its a 91 318i. Can any of you guys point out what it is, or what it does. Im planning on replacing it this weekend.

http://www.r3vlimited.com/board/attachment.php?attachmentid=100058&stc=1&d=1440205504

[roguetoaster]

That's your idle control valve. Its function is self explanatory.

[z28]

That's your idle control valve. Its function is self explanatory.

Thanks. If it controls the iddle, is it supposed to sound like a vacuum leak when its iddleling? The noise goes away when I give it some gas, and it iddles fine. Sorry for being a noob, but I'm used to Chevy ls engines only.

[roguetoaster]

I wouldn't presume that the ICV is the source of the leak, although it may buzz a bit. My first assumption would be that the brake booster valve is leaking, or failing that the grommet at the booster or another hose.

Vacuum leaks will appear to go away when you apply throttle. Spray some carb cleaner or similar around junctions and possible sources of leaks and look for bubbling in much the same way that you find a leak in a bicycle tube by submerging it in water.

Don't worry about being inexperienced, we are/were all there now/once.

[z28]

The brake booster valve, grommet, or hose could be my problem. I was moving the ICV around, and the vacuum leak sound would go away and come back with a very slight change in idle, but nothing drastic. The brake booster line is zip tied to the ICV, so it is likely moving when I wiggled the ICV. I did not have a lot of time to mess with it today because of work. I will see if I get some carb cleaner tomorrow and see what happens.

[z28]

Well I messed with it today and couldn't find anything, I used some carb cleaner removed the hoses and inspected them and nothing. All the hoses are good, check valve is good, and the grommet is good. With a closer inspection it seems like the noise is from inside the icv, but its sorta loud. Since the engine idles fine, drives fine, and no vacuum leaks.... I'm not gonna mess with it. Thanks for the help roguetoaster, I really appreciate it.

[Vanilla Gorilla]

If you want to have a good read when you are bored search for "Mess Under the Intake" is started on m42club.com and it spread around. It is a great read on how to eliminate the most problematic areas for vac leaks.

Enjoy the new car!

[z28]

If you want to have a good read when you are bored search for "Mess Under the Intake" is started on m42club.com and it spread around. It is a great read on how to eliminate the most problematic areas for vac leaks.

Enjoy the new car!

Thanks, will do.