Suspecting Vacuum leak...

[e34.535i.sport]

I've had a strange whistle noise developing over the past few weeks coming from somewhere i the general vicinity of the throttle linkage/intake manifold (I know that is a big area)... It happens when I release the throttle and at idle, although it is sporadic and random.

Other info that may be useful is that I have had a particularly rough idle for some time (Recent EAT chip improved it a little though), and it doesn't seem to have the same performance as it did when I got it (EAT chip has also improved this!).

After a lot of reading around it seems to suggest a vaccum leak - Pgrindstaff has been kind enough to reply to a PM I sent him as in one of his threads he describes symptoms exactly like mine.

I was hoping someone with m30 knowledge may be able to direct me to the vaccum hoses to check, or how I can differentiate these from other hoses at least so I can go find them and make sure there's no cracks etc, before looking at the intake manifold gasket. If there's anything else please suggest, and what methods I can use to check things as I'm fairly new to this vacuum business...

Pgrindstaff has suggested this small hose could be the issue and I am sure I have read this commonly causes a problem on the m30...
http://www.bimmernut.com/forum/showthread.php?t=37291&highlight=vacuum+hose

Oh and can I ask is this problem an urgent one to sort out? I'm assuming its ok to drive as long as there's no running problems - I just don't want to cause any damage by driving it with a vacuum leak...

TIA...

[whiskychaser]

Dont think its life and death but it may affect your mpg. Have you tried one of those carb cleaner sprays? I think the idea is you spray flammable cleaner on the suspect area and if your revs change you found the culprit

[e34.535i.sport]

Dont think its life and death but it may affect your mpg. Have you tried one of those carb cleaner sprays? I think the idea is you spray flammable cleaner on the suspect area and if your revs change you found the culprit

Hey you have a point there, I do get less mpg than I did when I bought it... Thanks for the spray idea, sounds like a plan... Just need to narrow it down a bit first I think...

[whiskychaser]

Hey you have a point there, I do get less mpg than I did when I bought it... Thanks for the spray idea, sounds like a plan... Just need to narrow it down a bit first I think...
Its good round the manifold area. So I hear. But dont go using your gas lighter refill cos its handy

[e34.535i.sport]

I had a leak from the fuel regulator on top of the engine block and it also made weird noises. Check that too, especially the small hose coming in from the passenger side.

Its funny you should say that becasue the FPR has been making wierd noises lately but seems to have quietened down and replaced by the whistle! I'll check that too thanks!

[Sixdown]

I had a leak from the fuel regulator on top of the engine block and it also made weird noises. Check that too, especially the small hose coming in from the passenger side.

[e34.535i.sport]

Hey guys, checked the two hoses that go through the manifold (one leads to the FPR and the other to the throttle body) I.e the two top purple ones in this pic...
http://www.nmia.com/~dgnrg/hose_map.jpg
*Courtesy of Gale - thanks!

I cant seem to find this 'Chrarcoal Cannister' vacuum line though, can anyone direct me to it? Never even heard of it before seeing this thread...

Had a look as well as I could at the intake gaskets and they seem ok, but there's definitely a gap somewhere...

Going to get some carb cleaner and spray it around a bit... Not too worried about the gasket job(if it is that) after doing some reading around. Thinking of doing injectors too if I end up doing the intake as they're a bit noisy at the moment.

The search continues.

[whiskychaser]

The search continues.
Fck. With a diagram like that you have to be a teacher!!!:)

[e34.535i.sport]

Fck. With a diagram like that you have to be a teacher!!!:)

LOL- If I had drew it you wouldn't be saying that believe me!!!!! :D

[whiskychaser]

LOL- If I had drew it you wouldn't be saying that believe me!!!!! :D
If I had drew it? I'm sure you didnt mean that sir:)

[ahlem]

Check the rubber "pipe" that connects the throttle body to the AFM for cracks too. If you have the original vacuum hoses on your fuel pressure regulator with the cloth covering, take a look at the ends underneath the cloth. they may be split after 18 years. The charcoal cannister is on the left inner fender area not too far from your oil filter. It's about the size of a 12 oz. can of beer. Follow the vacuum line from the fuel pressure regulator to the point it joins the under side of the intake manifold. How long has it been since the fuel filter was changed?

[e34.535i.sport]

Had a good inspection before, and I think I may have found the problem!

I had it running and pulled out the oil dipstick - Idle took a fit and was MUCH worse... I remember reading about this but can anybody remind me what it means?

The two thin lines through the manfold are sound, and it seems the intake gasket is too (haven't had chance to get carb cleaner yet though...)

I also got the ICV off (nearly snapped the metal bracket in the process) and checked the operation of the valve, it moved freely so I gave it a quick wipe and slapped it back on.

I continued to look around and found this pipe was about 1cm off where it should be... Anyone know what it is?! I took the air pipe for the alternator off so I could picture it easier...
http://img34.picoodle.com/img/img34/4/4/15/f_Image035m_631d614.jpg (http://www.picoodle.com/view.php?img=/4/4/15/f_Image035m_631d614.jpg&srv=img34)

So I pushed it back on...
http://img29.picoodle.com/img/img29/4/4/15/f_Image037m_4abffce.jpg (http://www.picoodle.com/view.php?img=/4/4/15/f_Image037m_4abffce.jpg&srv=img29)

Then I hit the JACKPOT I HOPE, (or lucked out as you guys call it?!) and noticed this ripped hose... I don't know what it is or where it attaches though, it is quite thick and under the throttle body/fuel rail area which is where a lot of the wierd noise is coming from... Have a look what do you think?
http://img33.picoodle.com/img/img33/4/4/15/f_Image038m_5b7a291.jpg (http://www.picoodle.com/view.php?img=/4/4/15/f_Image038m_5b7a291.jpg&srv=img33)

And another...
http://img01.picoodle.com/img/img01/4/4/15/f_Image039m_bb55db5.jpg (http://www.picoodle.com/view.php?img=/4/4/15/f_Image039m_bb55db5.jpg&srv=img01)

Please tell me this could be it, I'm really excited about having a nice idle that doesn't vibrate me off the seat!

[e34.535i.sport]

Check the rubber "pipe" that connects the throttle body to the AFM for cracks too. If you have the original vacuum hoses on your fuel pressure regulator with the cloth covering, take a look at the ends underneath the cloth. they may be split after 18 years. The charcoal cannister is on the left inner fender area not too far from your oil filter. It's about the size of a 12 oz. can of beer. Follow the vacuum line from the fuel pressure regulator to the point it joins the under side of the intake manifold. How long has it been since the fuel filter was changed?

Hey, Fuel filter changed in last 3k mile or so, badly needed doing as it had 1993 stamped on it and it was really heavy in comparison to the new one I put in!

I checked that hose you speak of fron the FPR but on mine there is no cloth covering. There is a cloth covering on the hose that goes to what I think is called a check valve? I'll post a pic later on today of it as the cloth has frayed and may be letting air in but I dont know...

Thanks for the info on the charcoal cannister, I'm going to have a look at that in a minute see if I can find it. The noise seems to come from close to the firewall but I know sounds can be deceiving.

Report back later...

[bmwpower]

Check the nipple on your brake booster hose check valve. It's supposed to have a rubber cap on the small nipple. Mine was recently cracked and I could hear a definite sucking sound, almost a whistle, when running.

That big "hose" is not a hose but a wiring loom... or at least I think it is since it looks like it's going into the wiring harness box.

Those other hoses are power steering lines.

[Sixdown]

The first two images look like the power steering hoses, but I am not sure if anything in that vicinity is a vacuum hose.

[e34.535i.sport]

Check the nipple on your brake booster hose check valve. It's supposed to have a rubber cap on the small nipple. Mine was recently cracked and I could hear a definite sucking sound, almost a whistle, when running.

That big "hose" is not a hose but a wiring loom... or at least I think it is since it looks like it's going into the wiring harness box.

Those other hoses are power steering lines.

Hey thanks... I thought they were powersteering lines as the big one in the picture goes to the PS pump, but the other one that I had to push back on goes straight to the front (by the grill somewhere) and the other end goed under the engine to the other side I assume...

This brake nipple sounds interesting, will have a look at this as soon as I finish work I think! Rough Idle is still a puzzler if the big ripped hose isn't it... I'm gutted.

[e34.535i.sport]

I've read around again and if the idle goes crappy when you pull out the oil dipstick its supposed to mean I have vacuum... So what the hell could the rough idle be - fuel pressure?! Don't think that would explain the whistle though...

This is a tricky one.

[AngryPopTart]

If I pull the dipstick out of my car nothing happens, but if I take the oil cap off the idle goes to crud. Also, that little check valve that attaches to the brake booster had a little hole in it, I presume where this nipple is supposed to be, and my Paps filled it with bondo cause he thought it was a leak, but I've still always had cruddy idle and I get this wierd whistling noise that changes with the shifts of the tranny, but is not the tranny whine itself. I unplugged the hole in the check valve and everything is the same, although I can put my finger over it and tell that it's got suction. Is it supposed to be plugged?

[e34.535i.sport]

Whistle turned out to be my clutch going! (See other thread for details!)

I feel like a muppet, but all the symptoms suggested vacuum leak... Grrrrr.