Vacuum Leak FAQ's

[pac0]

I figured that since I have this problem why not create a thread of FAQ's for everyone to reference. I will update all of your questions into this first post as well as those of you who can provide definite answers. Thanks in advance to all of you participating. Looking forward to creating more of these thread types.

Q: How can I test for a vacuum leak?
A: Pick up a can of carburetor cleaner and spray some underneath the intake manifold as well as around the intake. Make sure the engine is running, and if the idle changes, you have a vacuum leak.

Q: Would a vacuum leak throw the MAF (1215) code?
A: Yes, a vacuum leak can cause the MAF code 1215 to show up.

Q: My car seems to idle rough and stall out. Could this be due to a vacuum leak?
A: Yes, if there is a cracked or broken hose it may be the cause of a violent engine shake and even stalling.

Q: When I press the throttle my car stalls out. Can this be related to a leak?
A: Of course. If you are throwing a CEL (Check engine light) see if there are any MAF (1215) or IAT (1224) codes being thrown. A loose, broken, or cracked hose could cause the engine to die out once given throttle or during idle.

Q: I seem to be getting oil in my intake boot from the vacuum hose connected to the top of the valve cover. Can this be fixed?
A:

Q: I am getting an IAT sensor code (1224) being thrown. What will this effect and is it a crucial replacement?
A:

[tudragan]

i am having this same problem right now. my mechanic thinks that it does so can anyone else confirm this?

[pac0]

Updated. Can anyone throw down any questions or answers (or corrections)? Thanks!

[damone6969]

i know for my turbo supra, I bought a PVC endcap that would fit snug into one of my intercooler pipes, drilled a hole in it for a press in valve stem..

Put the cap into the pipe and pressurized it with an air compressor (guaged down to about 15-20psi) and a tire chuck.. worked GREAT for finding any tiny little boost leaks.. The air would charge into the intire intake system and you could hear leaks clear as day

I wonder if I could fabricate something for the E36 using the same principal

[pac0]

That's a great idea!! If you could come up with something of that sort I am sure it would benefit us all. Thanks!

[328iJunkie]

Carb cleaner and a running engine is all you need.

Spray around intake area and under intake manifold. If your idle changes =vac leak.

[drtweak1992325i]

this isnt quite a vaccum leak question but a vaccum related issue that others might have.

I get a LOT of oil coming back into my intake though the vaccume hose at the top of them valve cover. What could be causing this? What are possable fixes (besides oil catch can) can i do?

[328iJunkie]

Switch to the OBD2 separator system...?

[pac0]

How would you go about doing that? Are there any other fixes out there?

[alkumaish]

Some oil in your intake components is expected, but alot of it is a sign of a problem.

Our engines have a vacuum-sealed crankcase system. If there is a leak somewhere, you'll see a noticeable amount of engine oil deposits inside your intake components.

Possible leaks can be: Head cover gasket, oil cap gasket, dipstick o-rings (total of 3), oilpan gasket, and possibly a faulty head gasket or piston rings.

[drtweak1992325i]

Yea well i will see soon enough since everything that you mention is currently being replaced...

but is what your saying is that if there is a vaccum leak in one of these 3 areas it can cause more oil to flow though that tube back to the intake?

[alkumaish]

Yes...

The system is vaccum-sealed. So if there are any leaks allowing air into the system, oil will fume or evaporate more than usual.

Evaporated oil is allowed to escape (through the hose) into your intake so it can be burned.

[fun2drive]

I used a piece of PVC around 3" and a regular quick air connection plug to pressurize my intake a couple years back.
I used 5psi and found a couple minor leaks here and there but not the problem source.

I currently have a vacuum leak (I think) and will try the dip stick first since it is not reacting like it should when it is pulled out (no change in rpms which are low).

Next step is to pressurize the intake and see where leaks may show.
As an alternative I have a couple of silicon boots that will fit right on the intake without the ASC.

Oh and to answer the question of what does the IAT code throwing do to your engine?
It uses the temp reading along with a lot of other parameters to adjust the timing and fuel rates...

[Big Empty]

Pac0 places numbers infront of the questions so we can reference them.

Question #6: My Intake Air Temperature sensor was throwing code 1224. There was a lot of moisture in the intake so I dried it out and the code has not come back. While throwing the code, my car idled fine and i got the same gas mileage. No problems. I'd say its not crucial to replace, but then again mine was never essentially broken.

[toplessinokc]

I would like to have a diagram of the vacuum hoses on a 96 328i standard.

[fun2drive]

Here is one from realoem for the 2ndary air pump
http://www.realoem.com/bmw/showparts...39&hg=11&fg=45

This one is for the vapor recovery system which is also fed by the intake manifold
http://www.realoem.com/bmw/showparts...72&hg=13&fg=15

I didn't post the ones to the ICV as that is a large hose.

I will try to take pictures of my E36 M3 when I pull all this crap apart again to source the leak after I get around to pressure checking the intake man and then the valve cover. I will post them here once I get to it in a few weeks...

[toplessinokc]

Thanks for the links. One of our problems is we are putting two systems together. I will try to pull Real Oem pictures from both cars.
My son has put a 328 engine into his 318ti.
Now we are sorting out the little problems...

[SmokedBMW23]

I know, old thread but good info. Has anyone replaced the rubber vacuum hoses with silicone ones?

[DrinkCoffee]

I haven't personally, but it would work. Regular vacuum hose is only about $.9/foot so I just loaded up on that stuff and replaced all of the hoses.

[pac0]

I know, old thread but good info. Has anyone replaced the rubber vacuum hoses with silicone ones?

You can do this.. it would actually last much longer than the stock rubber hoses.