Help with vacuum hose??..

**BMWFAN** · 03-21-2005, 02:01 PM

I was under my hood yesterday and noticed that the big hose connected to the top of my valve cover was collapsed..I don't know how long it has been that way but I replaced it with another hose and now my car is idling rough as hell. Here are my questions:
1 what does that hose do
2 What is it connected to (other than the valve cover top)
3 Why is it causing my engine to idle rough after suposedly fixing it?

When I removed the hose I noticed lots of vacuum coming from the round flat thing it was connected to..

(95 318i automatic)

Thanks for you help!
Johnny

**GQ_Style** · 03-21-2005, 02:04 PM

You mean the hose that is coming out near the corner of the valve cover that is closest toward the engine fan? That is your crankcase breather hose. It connects to the bottom bung of your throttlebody and recirculates unburnt stuff into the combustion chamber for burn-off. It is probably really oily and nasty looking inside.

The replacement is like $10 or a simple 1/2 hose will do. Good luck.

**BMWFAN** · 03-21-2005, 02:07 PM

That is the hose but on my engine its at the rear...I replaced it and now it runs worse... any ideas?

**GQ_Style** · 03-21-2005, 02:09 PM

On a 95, you should have a M42 engine, which places the crankcase breather hose in the front, unless you have an M44 engine.

From the rear, are you sure it is not a vacuum hose?

**BMWFAN** · 03-21-2005, 02:20 PM

I have a m44 engine.

**GQ_Style** · 03-21-2005, 07:51 PM

I C, correct it goes to the bottom of your TB.

Why it runs terrible, I can only suspect more crumbled or loose hoses. Look and check.

**vml** · 03-21-2005, 08:44 PM

Originally Posted by BMWFAN

snip
1 what does that hose do
2 What is it connected to (other than the valve cover top)
3 Why is it causing my engine to idle rough after suposedly fixing it?
snip

1- already answered
2- That round black flat thing where the hose is connected to is the PCV valve which BMW calls "crankcase vent valve"
3- Maybe the PCV valve is bad or you removed another vacuum hose while working in the area?

**BMWFAN** · 03-21-2005, 09:19 PM

The PVC Valve is pulling a lot of vacuum...Is it supposed to? Here is another funny thing it is doing...When I pinch the hose shut (between the valve cover and the PVC valve)...the engine runs smooth as can be..Is that a sign of a bad valve?
Can I run the engine with the hose pinched shut temporarily?
Thanks,
Johnny

**Boondoggie** · 03-22-2005, 07:10 AM

Originally Posted by BMWFAN

The PVC Valve is pulling a lot of vacuum...Is it supposed to? Here is another funny thing it is doing...When I pinch the hose shut (between the valve cover and the PVC valve)...the engine runs smooth as can be..Is that a sign of a bad valve?
Can I run the engine with the hose pinched shut temporarily?
Thanks,
Johnny

You can run your engine for the rest of your life with that hose pinched shut... but you'll develop oil leaks...

Yes, it is supposed to pull a lot of vacuum, it's job is to draw the air out of the crankcase and into the intake manifold. If that hose is connected snugly, and it makes your car run poorly, then there is another air passage into the valve cover or "oil areas" that's acting as a gigantic vacuum leak. (I assume the oil cap is on?)

With the hose hooked up, and the engine running, remove the oil cap and put your palm over the opening. (not with the engine too hot, obviously) you should feel your hand gently sucked onto the engine. If not, air is getting into the crankcase somehow.

**BMWFAN** · 03-22-2005, 08:49 PM

On top of the pvc valve there is a little triangle with a thin slit on one end that is sucking air in...is it supposed to do that?

**BMWFAN** · 03-22-2005, 10:29 PM

I just did the hand on the oil opening trick and it is pulling....I got under the car and just noticed that I have an oil leak somewhere on the front of my engine! Could this be the source of the air coming in?

**BMWFAN** · 03-23-2005, 11:00 AM

^

**lorax** · 03-23-2005, 01:34 PM

i just did a m50 manifold swap on my '97 328is, and did not conect one of the vacuum tubes to the elbow behind the mass air flow meter, and infront of the traction control throtle body, this made my idle very choppy.. when i reconected it, the aditional vacume pulling through the Mass air flow meter fixed the idle. SO if there is a vacuum leak try disconecting the air flow meter... if you have one.. untill you can fix the leak.
good luck

**BMWFAN** · 03-23-2005, 03:41 PM

Can you tell me where the mass air flow meter is on my m44 engine?

**BMWFAN** · 03-23-2005, 07:44 PM

Ttt

**BMWFAN** · 03-24-2005, 09:17 AM

bump

**BMWFAN** · 03-25-2005, 01:11 PM

Any info?

**vml** · 03-25-2005, 01:41 PM

the MAF is in front of the throttle body and behind the air filter housing but you can just check for vacuum leaks by feel and by ear and also check for cracks from any of the hoses. I also assume that you changed the PCV valve.

**BMWFAN** · 03-25-2005, 04:39 PM

I havent changed the pvc valve yet...But it is pulling in air on the top of it....is it supposed to do that?

**BMWFAN** · 03-27-2005, 09:27 AM

More info HERE

**BMWFAN** · 03-29-2005, 05:03 AM

Problem was the crankcase vent valve..
Thanks for all of the help.

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