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durk96
Samba Member
Joined: June 05, 2005
Posts: 31
Location: san diego
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 Posted: Fri Aug 04, 2006 1:25 pm Post subject: Positive Crankcase Ventilation |
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Hi,
I just rebuilt the engine on my 73 bus and it has a small oil leak already. Has anyone tried to give their bus PCV? My dad says it will help prevent oil leaks by reducing pressure inside the crankcase.
Thanks,
sean |
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rsorak
Samba Member
Joined: March 07, 2005
Posts: 2005
Location: Memphis
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| Posted: Fri Aug 04, 2006 1:39 pm Post subject: |
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I thought about adding this to my engine too, but it doesn't leak enough to warrant the effort, so i never did. But i think it could be done as it's nothing more than tapping into your brake booster vaccuum line and adding a PCV valve and then connecting this to the breather on the oil filler. I'm reffering to a type 1 engine.
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Rick '71 Westfalia & '73 Thing |
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sluggo
Samba Member
Joined: August 17, 2005
Posts: 946
Location: Portland, Or.
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| Posted: Fri Aug 04, 2006 2:14 pm Post subject: Re: Positive Crankcase Ventilation |
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| durk96 wrote: |
Hi,
I just rebuilt the engine on my 73 bus and it has a small oil leak already. Has anyone tried to give their bus PCV? My dad says it will help prevent oil leaks by reducing pressure inside the crankcase.
Thanks,
sean |
On a Type IV, I'm pretty sure that's what the hose leading from the breather to the air cleaner is.
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pyrOman
Fire Master
Joined: July 21, 2003
Posts: 12570
Location: Over 2002 posts deleted!
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| Posted: Fri Aug 04, 2006 4:21 pm Post subject: |
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Some people are so busy being clever they don't have time enough to be wise. |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52727
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| Posted: Fri Aug 04, 2006 5:08 pm Post subject: |
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| The 411's and 412's used a true PCV system, which draws fresh air thru the crankcase and puts the case under a slight negative pressure at most times, don't know why VW didn't stick with it. The systems on most other Type 4 engines doesn't draw in fresh air and puts the crankcase under negligable vacuum. |
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SlowLane
Samba Member
Joined: July 11, 2005
Posts: 1044
Location: Livermore, CA
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| Posted: Fri Aug 04, 2006 9:21 pm Post subject: |
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| Wildthings wrote: |
| The 411's and 412's used a true PCV system, which draws fresh air thru the crankcase and puts the case under a slight negative pressure at most times, |
Y'know, I've heard/read about this, but I'm having trouble picturing how it would work. Do you know of any diagrams/references? I understand that this system used the valve cover vents that folks are often so keen on incorporating into their engines, but that the airflow actually went into the crankcase from the cover vents, rather than out. Is that right?
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Present:
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Back in the day:
'72 Super Beetle
'69 Camper Van - Corvair powered
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52727
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| Posted: Fri Aug 04, 2006 11:10 pm Post subject: |
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| Quote: |
| I understand that this system used the valve cover vents that folks are often so keen on incorporating into their engines, but that the airflow actually went into the crankcase from the cover vents, rather than out |
You are correct here, the air would go into the valve covers first and then into the crankcase. Except at full throttle when it would flow the other way as the manifold pressure drops to near zero.
The system is essentially the same as used on most other makes of cars from the late sixties onward. The PCV valve is a combination of a metering valve and a check valve (anti backfire valve). A little fresh air passing thru the crankcase keeps the oil free of moisture and many other contaminates. |
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josh
Samba Member
Joined: July 13, 2003
Posts: 1773
Location: laid back in the tall grass
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| Posted: Sat Aug 05, 2006 7:33 am Post subject: |
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| SlowLane wrote: |
| Y'know, I've heard/read about this, but I'm having trouble picturing how it would work. Do you know of any diagrams/references? I understand that this system used the valve cover vents that folks are often so keen on incorporating into their engines, but that the airflow actually went into the crankcase from the cover vents, rather than out. Is that right? |
Here it is. It's a little shady near the binding as I scanned it out of a book.
The stock setup used heads with ports in them, but ports added to the valve covers should work just as well. Be sure they get clean air from the air filter.
You will have to recalibrate your fuel mixture if you do this as it basically creates a controled vaccum leak.
This was used on 914's as well as 411's and 412's. Busses are the only type 4 powered vehicles that never came with it.
Type3's used an almost identical system from '72 on. |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52727
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| Posted: Sat Aug 05, 2006 10:30 am Post subject: |
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Has anyone actually seen a breather with the PCV valve sticking out of the bottom as shown in the drawing in Josh's post? I have seen pictures of larger breathers that overhung the tower but they appeared to ventilate out the top as well.
Maybe on the bus VW figured that there would seldom be enough manifold vacuum to get a PCV to function, so they just used a simple vent dumping into the intake on the busses. |
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SlowLane
Samba Member
Joined: July 11, 2005
Posts: 1044
Location: Livermore, CA
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| Posted: Sat Aug 05, 2006 10:55 am Post subject: |
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| Wildthings wrote: |
| Maybe on the bus VW figured that there would seldom be enough manifold vacuum to get a PCV to function, so they just used a simple vent dumping into the intake on the busses. |
I regularly see 18" of vacuum at idle on my engine, going up to 25" on overrun, so I don't think that's the reason.
Maybe the bus engine runs hotter than in the lighter vehicles, and so isn't as prone to moisture contamination?
More likely the beancounters at VW insisted on a cheaper system on the bus, since it would eventually account for the vast majority of type IV engines built. Cost is always a factor in engineering.
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Present:
'81 Westfalia: 2L, manual. Originally Canadian, now Californiated
Back in the day:
'72 Super Beetle
'69 Camper Van - Corvair powered
'71 Window Van - Transferred Corvair from '69
"With sufficient thrust, pigs fly just fine." - Internet RFC 1925
"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance." - Sir Terry Pratchett |
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rsorak
Samba Member
Joined: March 07, 2005
Posts: 2005
Location: Memphis
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| Posted: Sat Aug 05, 2006 10:58 am Post subject: |
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Buses never had PCV because they where considered trucks under US emissions laws and they weren't required.
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Rick '71 Westfalia & '73 Thing |
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josh
Samba Member
Joined: July 13, 2003
Posts: 1773
Location: laid back in the tall grass
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| Posted: Sat Aug 05, 2006 1:01 pm Post subject: |
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| rsorak wrote: |
| Buses never had PCV because they where considered trucks under US emissions laws and they weren't required. |
I don't think it was an emission requirement. I've never seen a PCV system on a bug, or lots of other cars built through the '70s and beyond.
I think they were just being cheap.
| Wildthings wrote: |
| Has anyone actually seen a breather with the PCV valve sticking out of the bottom as shown in the drawing in Josh's post? I have seen pictures of larger breathers that overhung the tower but they appeared to ventilate out the top as well. |
I've seen them on type3's. I have a type 3 book with the same diagram, so I think it's kind of generic.
The 914 breather that I have has the PCV on top. |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52727
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| Posted: Sat Aug 05, 2006 10:36 pm Post subject: |
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| The emissions wouldn't be any different between the PCV using a valve and just a vent hose running to the air intake as used on the busses. Either system should route all the crankcase fumes into the intake to be burned, so I doubt that it would be an emissions issue. I have always added some way to force a little fresh air into my crankcase to all my T1 and T4 engines, excepting my 411 which already had a good stock system. I never see that milky condensate in my engines that is typical of VWAC engines and have always gotten exceptional engine life. |
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dingo
Banned
Joined: July 19, 2004
Posts: 429
Location: eugene, OR
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| Posted: Sat Aug 05, 2006 10:57 pm Post subject: |
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| Quote: |
| I have always added some way to force a little fresh air into my crankcase to all my T1 and T4 engines, excepting my 411 which already had a good stock system |
so...how do you do that ? |
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josh
Samba Member
Joined: July 13, 2003
Posts: 1773
Location: laid back in the tall grass
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| Posted: Sat Aug 05, 2006 11:41 pm Post subject: |
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| dingo wrote: |
| so...how do you do that ? |
See the diagram above. |
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sun-bug74
Samba Member
Joined: July 14, 2020
Posts: 308
Location: Gloucester, MA
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| Posted: Sun Oct 29, 2023 6:09 am Post subject: Re: Positive Crankcase Ventilation |
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Hi, I need the black plastic part that sticks out of the top of the engine and has a hose over to the air cleaner. Crank case breather valve maybe? I am having trouble finding the part on line. This is for a 1978 bay with the 2.0 liter. Does anyone have a part number or a link?
Even after I tried to reseat and seal the existing valve, I am still getting substantial oil leaking that dribbles down through the engine and also blows around. As far as I can tell, it is all coming from that plastic valve.
Thanks.
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52727
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| Posted: Sun Oct 29, 2023 8:33 am Post subject: Re: Positive Crankcase Ventilation |
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| The original valve that bolts to the metal breather box is NLA. There is a thread here on the Samba that shows how to use a PCV from another rig. A bit of searching should turn it up. |
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dodger tom 
Samba Member
Joined: March 25, 2013
Posts: 2072
Location: Central Coast, CA, but we're all still Ukrainian and Californian
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 42955
Location: at the beach in Northern Wokistan
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| Posted: Sun Oct 29, 2023 10:30 am Post subject: Re: Positive Crankcase Ventilation |
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^^^ what Mike said.
I have only seen 5 of those valves NOS come up for sale in 15 - 20 years. Bob Hood found one, I had two about 10 years ago, used one and someone else took one for their restoration, found two others last year and they have both been passed on to others who wanted them. The only reliable other solution that I know of easy to acquire at this point is the later valve modification that is in the latest thread on the part. Be sure you follow instructions on how to point the valve. I know from talking with Dodger Tom this week that when he replaced his worn out original setup with the alternate solution, his valve cover gaskets stopped sucking in - which was a sign that the case had too much vacuum in it from a bad PVC.
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sun-bug74
Samba Member
Joined: July 14, 2020
Posts: 308
Location: Gloucester, MA
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| Posted: Sun Oct 29, 2023 11:39 am Post subject: Re: Positive Crankcase Ventilation |
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I will send a pic to be sure we are talking about the same thing. What allows the oil to leak out, an actual failure of the valve?
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