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Rhythmic humming at startup - Oil trap related?

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo XC90s. The XC90 proved to be very popular, and very good for Volvo's sales numbers, since its introduction in model year 2003 (North America).
Woodguy
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Rhythmic humming at startup - Oil trap related?

Post by Woodguy »

Hey all, this is my first time posting in the three years I have owned my 2007 XC90 3.2L and have appreciated all of the tips I have found here over the years. Since I have not found answers related to my issues here, I am hoping to get some solutions that I, as well as others could benefit from.
My 2007 XC90 has 147,000mi on it and in April of '19 I had the oil trap humming/squealing, as many others have had, and replaced the oil trap deflector with a genuine Volvo oil trap deflector and everything worked great until a couple months ago (October '19) where it started this rhythmic humming at start up, which starts immediately after the vehicle idles down to 1000rpms approx.or at about 15-30 seconds after it has been started. It is hard to say but the humming might last for 10mi or less, or until it is really warmed up. It is hard to say when it stops because you can't hear it while driving as it is at a low enough frequency from the engine bay. The humming had got louder over the weeks and seemed to last for a longer duration as I would notice the sound even after driving for a while I could still hear it a stop light if I rolled the window down.
When I pulled the dipstick the humming would go away and when the dipstick was put back in it would still continue the rhythmic humming (1sec on 2sec off) or it would do a constant hum until it went away.
Fast forward to a couple of weeks ago I purchased another genuine Volvo oil trap deflector from FCP Euro and it almost started the rhythmic humming right away, too. Again, the humming goes away when I pull the dipstick, however, I am now noticing an oil leak from under the engine and on the drivers side (oil midway up block on drivers side). When it is humming I put my hand on the oil deflector diaphragm cover and you can hear and feel the humming from the cover. I have tried to tighten the oil cover deflector bolts, thinking they may have come loose. I don't know what else this could be and now fear that this engine pressure/suction has caused some kind of engine seal leak. We are wanting to sell this vehicle to buy a van but I want to make sure the vehicle is sound and safe before doing so.

Thank you for your answers in advance!

-Woodguy
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Rhythmic oil trap humming - audio
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oragex
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Re: Rhythmic humming at startup - Oil trap related?

Post by oragex »

The dipstick thing may indicate indeed a faulty PCV or related hoses. When servicing this, we need to replace the box and all hoses, including the PTC nipple. Not sure what brand was used, but Uro PCV may not last long. Also make sure to use Oeticker clamps on all hoses, not worm clamps (these loosen up under vibrations) Try this PCV test www.youtube.com/watch?v=gK8kUQxhT_8
Woodguy
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Re: Rhythmic humming at startup - Oil trap related?

Post by Woodguy »

So, with my 3.2 L 6-cylinder engine, I don't see where there is a breather box with hoses. The PCV valve/oil trap on my vehicle is on top of the engine and near the firewall and has no hoses coming in or out of it. I would be grateful if you could send me pictures or engine diagrams as to where I could find it on a 3.2 L engine.

Thank you!
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Re: Rhythmic humming at startup - Oil trap related?

Post by RickHaleParker »

Woodguy wrote: Mon Jan 13, 2020 4:37 pm I would be grateful if you could send me pictures or engine diagrams as to where I could find it on a 3.2 L engine.
The crankcase ventilation is maintained internally in the engine.
An oil separator is on top of the engine's camshaft cover. It separates the oil drops from the air in the crankcase. The drops are collected in a separator and flow back inside the engine to the oil pan. This prevents extra weight and space for external pipes.
3.2_PCV.gif
3.2_PCV.gif (107.24 KiB) Viewed 190 times
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Woodguy
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Re: Rhythmic humming at startup - Oil trap related?

Post by Woodguy »

Thanks for the info, RickHaleParker! This is what I had originally thought as I had not seen any other hoses wen I have replaced the oil trap twice now in less than 1yr. Still not sure why vehicle is making this noise like something is still plugged up. Last time I changed the trap I lightly blew air through the two openings in the engine block to try to break any unseen obstructions loose. There was nothing visibly blocking anything. I was reading about the charcoal canister but not sure if that could be correlated or not?
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Re: Rhythmic humming at startup - Oil trap related?

Post by RickHaleParker »

Woodguy wrote: Mon Jan 13, 2020 8:50 pm Last time I changed the trap I lightly blew air through the two openings in the engine block to try to break any unseen obstructions loose
Chase them with Oil Gallery brushes. A full set runs ~$30.00 on eBay.

Pull the dipstick and put your finger over the end of the tube when it is making the noise.
1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package.
2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000.
2004 S60R, B8444S TF80 AWD.
2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0.
Woodguy
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Re: Rhythmic humming at startup - Oil trap related?

Post by Woodguy »

Ok, I think I will get a set of oil gallery brushes and drop the oil pan, too. I will see if there is a pcv breather port that could be plugged or if the oil is sludge-like. I got the vehicle with 113k mi, now 148K, and I run 5W-30 Castrol Edge or Mobile1 high mileage and use Napa gold or Mahle oil filters and change at the 7,500mi or sooner to prevent crap like this.

Thanks
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Re: Rhythmic humming at startup - Oil trap related?

Post by oragex »

High mileage oils are not so good. I suggest Castrol or Mobil 0W-30 or 0W-40, a much better oil. Helps the engine warm up faster and less wear at cold start up. The 0W-30 Castrol is quite amazing, mine stayed clear for very long (but also expensive) Mahle filter is good, but Mann appears to be OEM for your engine https://www.fcpeuro.com/Volvo-parts/XC9 ... d=836&v=98
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Re: Rhythmic humming at startup - Oil trap related?

Post by mieses »

Did you figure it out?

Our 2008 XC70 3.2L has identical symptoms. The PCV would squeal. I replaced the PCV oil trap at 130k mi (Volvo Part # 31319642) and found that the diaphragm had torn. A few weeks later the rhythmic hum at low RPM's started. The hum is identical to your recording and comes from the diaphragm on the PCV. It goes away after a few minutes of driving.
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Re: Rhythmic humming at startup - Oil trap related?

Post by SuperHerman »

I am not familiar with the 3.2L, but does the system use a secondary air injection system at start up?

I played the video and offended my cat. It sounds like a PCV issue - diaphragm related. I had similar on a BMW and that was the cause.
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