Hissing Vacuum Line?

cjdzombie · 12-29-2017, 07:13 PM

I'm wrapping up some maintenance work on my engine. I noticed a hiss sound when I was connecting the line picture with the yellow writing and screw. If I slightly bend the line at the connection piece I hear a hiss. This is before ai even started the engine. Guess there is still some pressure in the engine. Is this a leak of some kind? Doesn't seem right.

juld0zer · 12-30-2017, 02:30 AM

That is the vacuum feed to the reservoir in your rocker cover, which the wastegate and exhaust flap are supplied from.

Im having difficulty understanding when you heard the hiss and where you disturbed it. If the engine is off and you tried to pull up on it, it will hiss because there is no check valve going to the reservoir. If any hoses are disconnected with the engine off in this circuit you will deplete the vacuum in this circuit.

cjdzombie · 12-30-2017, 07:37 PM

I was hearing the noise after screwing the tube back in. When I slightly bent the tube at the connection point with the screw it hissed. I double checked the tube this morning and then started the car. After letting the car get to temp I did some random pulls with no issues, so not sure what it was or if it is an issue. Any idea on the part number of the tube in case I would need replace down the road?

juld0zer · 12-31-2017, 06:19 AM

If it does not hiss when it is undisturbed, don't go provoking it. The pipe should never move much in normal operation because there is a small channel on top of the rocker cover where it slots loosely into.

It can be replaced but only as a complete assembly from the quick release fitting on the valve cover to the check valve that screws into the vac pump.

The small seal on the check valve can also leak.

12-29-2017, 07:13 PM	#1
cjdzombie First Lieutenant 76 Rep 290 Posts Drives: 2011 E92 335i xDrive, M Sport Join Date: Dec 2015 Location: Cincinnati iTrader: (0)	I'm wrapping up some maintenance work on my engine. I noticed a hiss sound when I was connecting the line picture with the yellow writing and screw. If I slightly bend the line at the connection piece I hear a hiss. This is before ai even started the engine. Guess there is still some pressure in the engine. Is this a leak of some kind? Doesn't seem right. Attached Images __________________ 2011 E92 335i xDrive M-Sport MHD 93 Stage 2+ \| xHP Stage 3 \| xDelete \| Catless Downpipe \| Phoenix Racing Intercooler \| ARM CP \| AFE Drop In Filter
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12-30-2017, 02:30 AM	#2
juld0zer Lieutenant Colonel 480 Rep 1,600 Posts Drives: Prev 135i 7DCT, Now 130i 6sp Join Date: Jul 2016 Location: 2153 iTrader: (0)	That is the vacuum feed to the reservoir in your rocker cover, which the wastegate and exhaust flap are supplied from. Im having difficulty understanding when you heard the hiss and where you disturbed it. If the engine is off and you tried to pull up on it, it will hiss because there is no check valve going to the reservoir. If any hoses are disconnected with the engine off in this circuit you will deplete the vacuum in this circuit.
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12-30-2017, 07:37 PM	#3
cjdzombie First Lieutenant 76 Rep 290 Posts Drives: 2011 E92 335i xDrive, M Sport Join Date: Dec 2015 Location: Cincinnati iTrader: (0)	I was hearing the noise after screwing the tube back in. When I slightly bent the tube at the connection point with the screw it hissed. I double checked the tube this morning and then started the car. After letting the car get to temp I did some random pulls with no issues, so not sure what it was or if it is an issue. Any idea on the part number of the tube in case I would need replace down the road? __________________ 2011 E92 335i xDrive M-Sport MHD 93 Stage 2+ \| xHP Stage 3 \| xDelete \| Catless Downpipe \| Phoenix Racing Intercooler \| ARM CP \| AFE Drop In Filter
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12-31-2017, 06:19 AM	#4
juld0zer Lieutenant Colonel 480 Rep 1,600 Posts Drives: Prev 135i 7DCT, Now 130i 6sp Join Date: Jul 2016 Location: 2153 iTrader: (0)	If it does not hiss when it is undisturbed, don't go provoking it. The pipe should never move much in normal operation because there is a small channel on top of the rocker cover where it slots loosely into. It can be replaced but only as a complete assembly from the quick release fitting on the valve cover to the check valve that screws into the vac pump. The small seal on the check valve can also leak.
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