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jkmcrg
Samba Member
Joined: November 24, 2014
Posts: 169
Location: Austin, TX
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 Posted: Mon Aug 03, 2015 8:13 am Post subject: Crankcase Breather Vacuum Leak |
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Hey y'all. I've been chasing down a vacuum leak and I have isolated it to the crankcase breather valve. When I disconnect the breather valve hose from the intake boot and blow into it, I hear a hissing bubbling sound, but I can't pinpoint where it is. It sounded like it was coming from the base, so I took off the tower, cleaned the seal and connection, RTV'd it, then blew in it again and same hissing. Does that mean there's a leak in the crankcase? Where else in the system could be bubbling and hissing like that?
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1984 Westfalia Orwell (crispy)
2.2L Digifant
Automatic transmission |
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jkmcrg
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Joined: November 24, 2014
Posts: 169
Location: Austin, TX
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| Posted: Fri Aug 07, 2015 9:58 am Post subject: |
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Blew some smoke into the system and isolated it to the oil dipstick tube. Looks like I just need a new o-ring and hopefully all my woes are gone
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1984 Westfalia Orwell (crispy)
2.2L Digifant
Automatic transmission |
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jkmcrg
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Joined: November 24, 2014
Posts: 169
Location: Austin, TX
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| Posted: Mon Aug 17, 2015 4:35 pm Post subject: |
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bump!
I sealed the dipstick tube and smoke tested the system again, and now there's smoke coming out of the breather tower check port! Is this normal? I read about this port but I'm not 100% sure if it's meant to be open to air. Is the tower bad or is this expected behavior? thanks!
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1984 Westfalia Orwell (crispy)
2.2L Digifant
Automatic transmission |
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Ahwahnee
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Joined: June 05, 2010
Posts: 9797
Location: Mt Lemmon, AZ
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| Posted: Mon Aug 17, 2015 7:18 pm Post subject: |
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My understanding of the breather is that it is more or less a controlled vacuum leak. Crankcase pressure has to go somewhere.
What was the original problem/symptom you were trying to address?
You might also mention what year you have as this set-up changed along the way. |
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djkeev
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Joined: September 30, 2007
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Location: Reading Pennsylvania
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djkeev
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Ahwahnee
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Joined: June 05, 2010
Posts: 9797
Location: Mt Lemmon, AZ
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| Posted: Tue Aug 18, 2015 9:43 am Post subject: |
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| djkeev wrote: |
| ...I'd for sure install a restrictor down to 5.5mm. |
I used a plastic plug from the plumbing section as at Ace Hardware:
I then drilled a 5.5mm hole in it (7/32" drill will do) and stuck the plug in the outlet of the breather tower and pushed the hose on over it.
This was on an 84 so perhaps yours will differ (though I think not as the same tower was used). |
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jkmcrg
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Joined: November 24, 2014
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Location: Austin, TX
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| Posted: Tue Aug 18, 2015 11:01 am Post subject: |
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Okay I thought the valve was controlling the flow of air between the crank case and the intake boot. But is the diagram saying that the valve actually controls if it's pulling in outside air or not?
I already have the restriction to the s boot in my heating element.
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1984 Westfalia Orwell (crispy)
2.2L Digifant
Automatic transmission |
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Merian
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Joined: January 04, 2014
Posts: 5212
Location: Orygun
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| Posted: Tue Aug 18, 2015 12:51 pm Post subject: |
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piston rings do not seal perfectly, creating blowby
the blow by raises the pressure in the crankcase, and like the man said
it has to go somewhere, hence the need for a vent (usually to the intake where the oil vapor can be burned) |
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jkmcrg
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Joined: November 24, 2014
Posts: 169
Location: Austin, TX
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| Posted: Tue Aug 18, 2015 12:58 pm Post subject: |
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I understand that the tower is there to combust crank case vapor build up, my question is if the tiny port on the underside of the rim of the tower that's not in the diagram should be open to outside air.
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1984 Westfalia Orwell (crispy)
2.2L Digifant
Automatic transmission |
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jkmcrg
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Joined: November 24, 2014
Posts: 169
Location: Austin, TX
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| Posted: Sun Aug 23, 2015 1:51 pm Post subject: |
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Okay I'm pretty confident that port shouldn't be open to air. Ordered a new one from Gowesty and installed it the other day, and my crap idle is now proud and strong!
With the old tower, I could plug the bottom and blow in the top and hear a hissing, with the new tower, it seems to be airtight from both ends (in fact, there is no little port at all on the one I received).
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1984 Westfalia Orwell (crispy)
2.2L Digifant
Automatic transmission |
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ALIKA T3
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Location: Honolulu,Hawaii and France
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porterbrown
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Location: Bentonville, AR
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| Posted: Sun Aug 23, 2015 4:04 pm Post subject: |
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Stole this pic from another thread. Is the tiny vent in the pic the "port" that's being referenced here?
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ALIKA T3
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davideric9
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Joined: January 21, 2009
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Location: Oakland CA
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| Posted: Sun Aug 23, 2015 5:53 pm Post subject: |
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If that little square hole is sucking in air then the diaphragm is shot and not doing its job, its job being to restrict the flow of crankcase gases when intake vacuum is high.
I installed a new breather tower and had a fountain of oil all over the engine and sprayed across the back of the van after about 30 minutes on the freeway. Quite the mess. I punched a hole in the underside of the lip (with wife's knitting needle on the side of the road) and continued on my way, no more oil escaping.
I figured the valve was stuck in the closed position (due to manufacturing process) with air pocket trapped above the valve preventing it from opening and creating high pressure in the crankcase forcing oil out of the dip stick and filler tube.
That little vent hole in necessary for the valve to operate as it is vacuum actuated.
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1987 Syncro Westfalia, stock (bought 1994)
1986 Syncro Westfalia SVX, 3 knob (bought 2008)
1987 Westfalia (bought 2010)
1988 Wolfsburg GL (bought 2012) |
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davideric9
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| Posted: Sun Aug 23, 2015 8:30 pm Post subject: |
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Just occurred to me that the restrictor plate may be needed to restrict vacuum from the breather valve NOT to restrict the amount of air entering the throttle body from the crank case... Less vacuum to keep the valve open longer and only close under highest vacuum at idle.
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1987 Syncro Westfalia, stock (bought 1994)
1986 Syncro Westfalia SVX, 3 knob (bought 2008)
1987 Westfalia (bought 2010)
1988 Wolfsburg GL (bought 2012) |
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Wildthings
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| Posted: Sun Aug 23, 2015 11:09 pm Post subject: |
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| davideric9 wrote: |
| Just occurred to me that the restrictor plate may be needed to restrict vacuum from the breather valve NOT to restrict the amount of air entering the throttle body from the crank case... Less vacuum to keep the valve open longer and only close under highest vacuum at idle. |
The valve is opened and closed mainly by crankcase pressure and thus maintains a fairly constant crankcase pressure regardless of the amount of blowby.
If the diaphragm is bad then closing off the bleed hole would seal off a vacuum leak at that location. |
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davideric9
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Joined: January 21, 2009
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Location: Oakland CA
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| Posted: Mon Aug 24, 2015 6:52 am Post subject: |
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Wildthings wrote:
| Quote: |
| The valve is opened and closed mainly by crankcase pressure and thus maintains a fairly constant crankcase pressure regardless of the amount of blowby. |
"The breather valve operates via intake manifold vacuum.... The valve is closed as spring pressure on the valve seat is overcome."
Overcome by vacuum, not crankcase pressure. The valve is held open by a spring, not crankcase pressure, and less crankcase pressure will not overcome a spring. With engine off, the valve is open, only vacuum will close the valve.
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1987 Syncro Westfalia, stock (bought 1994)
1986 Syncro Westfalia SVX, 3 knob (bought 2008)
1987 Westfalia (bought 2010)
1988 Wolfsburg GL (bought 2012) |
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Wildthings
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| Posted: Mon Aug 24, 2015 8:20 am Post subject: |
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| davideric9 wrote: |
Wildthings wrote:
| Quote: |
| The valve is opened and closed mainly by crankcase pressure and thus maintains a fairly constant crankcase pressure regardless of the amount of blowby. |
"The breather valve operates via intake manifold vacuum.... The valve is closed as spring pressure on the valve seat is overcome."
Overcome by vacuum, not crankcase pressure. The valve is held open by a spring, not crankcase pressure, and less crankcase pressure will not overcome a spring. With engine off, the valve is open, only vacuum will close the valve. |
Wrong is wrong even if it is in the manual. The spring presses the valve shut and no amount of vacuum high or low isn't going to open it. The only force to open the valve is the crankcase pressure against the diaphragm. Note that most of the diaphragm is exposed to crankcase pressure and very little is exposed to in always minor vacuum of the S-boot. Also note that no part of the diaphragm is EVER exposed to manifold vacuum, EVER. It is exposed to S-boot vacuum which is pretty much the minor pressure drop across the air cleaner element and the AFM. |
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davideric9
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| Posted: Mon Aug 24, 2015 8:36 am Post subject: |
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Gosh, this won't be resolved in this manner. The breather tower I cut open yesterday had a spring holding the diaphragm away from the opening, so the valve is open until the spring is compressed. Maybe the one you cut open was built differently. Would a photo of the parts convince you? Lets just agree to disagree and leave it for others to decide for themselves...
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1987 Syncro Westfalia, stock (bought 1994)
1986 Syncro Westfalia SVX, 3 knob (bought 2008)
1987 Westfalia (bought 2010)
1988 Wolfsburg GL (bought 2012) |
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