Unknown hose leaking oil?

tobeydw · 09-08-2020, 02:12 AM

Hey guys, trying to trace down an oil leak.

Not entirely sure what this line is, but any help would be appreciated. Also, this may or may not be related, but all the PCV hoses and PCV itself was changed yesterday, so that might be apart of the leak, but pretty sure it's not leaking anymore.

I'm thinking it may also be my valve cover gasket, or oil pan gasket. Will be getting those done shortly.

Here's a video of the issue:

Steve Sas · 09-08-2020, 07:48 AM

Vacuum pump for brake booster.

e91Owner · 09-09-2020, 02:42 AM

Quote:

Originally Posted by tobeydw

Hey guys, trying to trace down an oil leak.

Not entirely sure what this line is, but any help would be appreciated. Also, this may or may not be related, but all the PCV hoses and PCV itself was changed yesterday, so that might be apart of the leak, but pretty sure it's not leaking anymore.

I'm thinking it may also be my valve cover gasket, or oil pan gasket. Will be getting those done shortly.

Here's a video of the issue:

If you have a dental mirror, look underneath your oil filter housing where it meets the block. The oil filter housing gasket is a common leak source and is cheap and relatively easy to replace. If you don't have a mirror, just wipe a paper towel underneath it to see if there is any fresh oil.

Efthreeoh · 09-09-2020, 01:19 PM

You are convolving two different things, which is leading to confusion. The N52 engine does not use a throttle plate to control engine speed, it uses something called Valvetronic, which throttles the engine using valve lift and duration. Because of the missing throttle plate, the N52 makes very little manifold vacuum. To create the missing vacuum, BMW added a vacuum pump to the engine. The hose you pointed at, as Steve Says said, is the main vacuum line from the vacuum pump to the brake booster (all power brakes use vacuum to power the brake pedal so it is easier to push).

Being a hose, you are naturally thinking it is leaking oil, but it has no oil in it, just vacuum. The oil is leaking from the oil filter housing on to the side of the engine block under the intake manifold. The engine is canted to the right side (exhaust side) so there is a valley under the intake manifold that will collect oil leaking from the OFHG, or in some cases the valve cover gasket, or sometimes both.

Most likely it is the oil filter housing. An easy repair if you are a capable home mechanic. There is a good DIY for the OFHG repair in the DIY subforum.

tobeydw · 09-09-2020, 08:29 PM

Thank you all, will get my OFHG repaired, and go from there. Just curious then, how come the hose is wet? You can clearly see in the video that it is wet. If it's just vacuum, it should just be air, no?

09-08-2020, 02:12 AM	#1
tobeydw Enlisted Member 3 Rep 31 Posts Drives: 2006 330i Join Date: Jul 2020 Location: Morgan Hill, CA iTrader: (0)	Unknown hose leaking oil? Hey guys, trying to trace down an oil leak. Not entirely sure what this line is, but any help would be appreciated. Also, this may or may not be related, but all the PCV hoses and PCV itself was changed yesterday, so that might be apart of the leak, but pretty sure it's not leaking anymore. I'm thinking it may also be my valve cover gasket, or oil pan gasket. Will be getting those done shortly. Here's a video of the issue:
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09-08-2020, 07:48 AM	#2
Steve Sas Private First Class 24 Rep 144 Posts Drives: BMW 335i 2008 Join Date: May 2020 Location: Sydney iTrader: (0)	Vacuum pump for brake booster.
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09-09-2020, 01:19 PM	#4
Efthreeoh General 19915 Rep 19,257 Posts Drives: The E90 + Z4 Coupe & Z3 R'ster Join Date: May 2012 Location: Verginny iTrader: (0)	You are convolving two different things, which is leading to confusion. The N52 engine does not use a throttle plate to control engine speed, it uses something called Valvetronic, which throttles the engine using valve lift and duration. Because of the missing throttle plate, the N52 makes very little manifold vacuum. To create the missing vacuum, BMW added a vacuum pump to the engine. The hose you pointed at, as Steve Says said, is the main vacuum line from the vacuum pump to the brake booster (all power brakes use vacuum to power the brake pedal so it is easier to push). Being a hose, you are naturally thinking it is leaking oil, but it has no oil in it, just vacuum. The oil is leaking from the oil filter housing on to the side of the engine block under the intake manifold. The engine is canted to the right side (exhaust side) so there is a valley under the intake manifold that will collect oil leaking from the OFHG, or in some cases the valve cover gasket, or sometimes both. Most likely it is the oil filter housing. An easy repair if you are a capable home mechanic. There is a good DIY for the OFHG repair in the DIY subforum.
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09-09-2020, 08:29 PM	#5
tobeydw Enlisted Member 3 Rep 31 Posts Drives: 2006 330i Join Date: Jul 2020 Location: Morgan Hill, CA iTrader: (0)	Thank you all, will get my OFHG repaired, and go from there. Just curious then, how come the hose is wet? You can clearly see in the video that it is wet. If it's just vacuum, it should just be air, no?
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