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poor-sche
Joined: 06 Jan 2017 Posts: 80 Location: Los Angeles, CA
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Posted: Sun Feb 25, 2018 12:40 pm Post subject: Oil in my air box |
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My car has been running great, but it drips oil after driving. While trying to find the source of the oil leak(s) on my S1-931, I found this in my air box...
I took apart the Air/Oill separator, but the inside was actually not that bad. Just a lot of carbon buildup that easily cleaned up with a little scraping.
Further down the rabbit hole I went. I removed the intake manifold to get to the crankcase breather. Someone decided to attach the non-hex head hose clamp facing down so that the only way to remove it while the engine is still in is to cut it off with a
With the hose finally off...
Here’s what the inside of the breather looks like.
Does this look right? Is something missing? How should I go about cleaning it? Am I barking up the wrong tree? Should I have just checked compression? _________________ 1980 - 931 |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Sun Feb 25, 2018 11:33 pm Post subject: |
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Turbos breath a lot of oil vapour. Condenses and collates in the air box and intake system. Worth checking out and cleaning. But will return. _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252 |
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peterld
Joined: 10 Dec 2006 Posts: 947 Location: Noosa Heads QLD Australia
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Posted: Wed Feb 28, 2018 6:42 pm Post subject: |
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These motors, even when in rude health, are heavy breathers. As the motor wears (piston/ring/cylinder walls) even more blowby is evident. The block vents to the air/oil separator where the droplets are hopefully caught, and the oily air passes onto the fuel distributor. Any oil caught in the separator drains back to the sump.
Your bottom picture of the block vent shows years of oily buildup. This could just be from years of running or could indicate heavy wear problems in the motor.
To get some idea of the condition of the motor, all things being equal, you need to clean out the vent, the separator and your airbox. Then further running will indicate the severity of the blowby (amongst other things)
Cleaning the vent is easy with the motor out, but almost impossible with the motor insitu. The vent is a hard press-in fit into the block, which is almost impossible to access with levers/etc while insitu.
On various motors I have worked on I have found the vent in numerous cases to be clogged solid (which yours almost appears to be). It has taken serious elbow grease to to dislodge the burnt/baked on tar.
This system was part of the emissions regime at the time. It is what it is. _________________ 80/81 932/8 ROW |
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Eric P
Joined: 21 Jun 2017 Posts: 175 Location: NY, USA
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Posted: Wed Feb 28, 2018 11:19 pm Post subject: |
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Maybe someone can chime in on this. On my NA, there was a restrictor in the hose. It was basically a chunk of rubber with a 1/4" hole through it. It was molded inside the hose so it isn't shown on the PET. When I replaced my vent with radiator hose, I machined up a chunk of aluminum to fit in there and slow down the air flow through the vent.
Does the 931 have this? If so, it's possible somebody replaced your vent hose and didn't put a new restrictor in there? I'd bet that could cause a lot of oil in the intake if you have too much air flow through the breather hose.
*** This is just a guess. I don't know if the 931 and 924 have this in common as I don't have a 931. _________________ 1980 924 NA, US model
1987 924S, US model |
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poor-sche
Joined: 06 Jan 2017 Posts: 80 Location: Los Angeles, CA
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Posted: Thu Mar 01, 2018 2:47 pm Post subject: |
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I’m pretty sure I read the 931 didn’t have the restrictor in the hose. My hoses look to be original and there definitely isn’t one.
I would agree that removing the breather while the engine is in, without destroying it, would be damn near impossible. I’ve yet to see what the inside of a clean one looks like. Mine doesn’t appear to be clogged in my opinion, but I don’t know how clean it should be? I can stick my pinky into the tube and feel that there is a gap between the outer housing and inner “baffle”? Any ideas?
And for anyone interested in what the inside of the air/oil separator looks like, here’s mine with the cap off. The inside walls were covered in carbon buildup that came off easily with a little scraping. I plan on adding some steel wool and sealing it back up with silicone, so that I can reopen it easily if necessary. I read somewhere in an older thread that the wool acts like a baffle to help mitigate some of the oil in the air box. I suppose I should also make sure that the return line to the sump is clear as well.
_________________ 1980 - 931 |
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Eric P
Joined: 21 Jun 2017 Posts: 175 Location: NY, USA
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Posted: Thu Mar 01, 2018 11:20 pm Post subject: |
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I personally wouldn't put steel wool anywhere near the internals of my engine. Steel wool tends to shed small bits of metal over time and it would work its way into your oil. If you really want to put something in there, I would lean towards one of those stainless steel pot scrubbers. They have much larger fibers and don't fall apart like steel wool will. I'd imagine you would have to put a lot of baffling material in there to make a difference. It looks like you would have to fill the cavity to the top.
Even if the 931 didn't come with a restrictor in the hose, I wonder if adding one would cause any issues? It works surprisingly well on the NA. Again, someone else will probably need to provide insight on that. Maybe a turbo builds crankcase pressure a lot faster than an NA and can't have a tiny vent? _________________ 1980 924 NA, US model
1987 924S, US model |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Thu Mar 01, 2018 11:36 pm Post subject: |
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Don’t put anything steel in the Purolator. Obvious reasons
Don’t restrict the crank case breather hose either on a turbo. You will cause other issues in the system. Intake system under vacuum pulls positive sump pressure out for a reason. If you don’t want oil vapour going into the intake system, then use a vent to atmosphere oil catch can instead of the purolator. Recommended for higher boost engines. Not needed on stock boost. But you will end up with oil vapour build up in the engine bay which will need cleaning periodically.
Engines breath oil vapour. Turbo engines breath more oil vapour than NA _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252 |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Fri Mar 02, 2018 12:30 am Post subject: |
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First, be aware that those breathers are NLA from Porsche, so you don't want to damage it in any way.
Secondly, you can try back-flushing thru the breather. Start with gasoline and see if you can get the worst of the sludge flushed down into the oil pan. Obviously, drain the existing oil first. Multiple flushes followed by some compressed air blasts should help. Be sure to VERY thoroughly flush the oil pan...lift the front of the car as high as you can get it to encourage all of the sludge to come out of the drain plug.
As noted above, 931s did not have a dowel in the breather hose, that was only for NAs. _________________ erstwhile owner of just about every 924 variant ever made |
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poor-sche
Joined: 06 Jan 2017 Posts: 80 Location: Los Angeles, CA
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Posted: Fri Mar 02, 2018 6:02 am Post subject: |
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Eric P wrote: | I personally wouldn't put steel wool anywhere near the internals of my engine. Steel wool tends to shed small bits of metal over time and it would work its way into your oil. If you really want to put something in there, I would lean towards one of those stainless steel pot scrubbers. They have much larger fibers and don't fall apart like steel wool will. I'd imagine you would have to put a lot of baffling material in there to make a difference. It looks like you would have to fill the cavity to the top. … |
Oops! You’re right, stainless steel pot scrubber is what I was thinking.
Carrera RSR wrote: | Don’t put anything steel in the Purolator. Obvious reasons… |
Do you think the stainless steel ball would come apart and make its way back into the sump?
ideola wrote: | First, be aware that those breathers are NLA from Porsche, so you don't want to damage it in any way.
Secondly, you can try back-flushing thru the breather. ... |
Thanks for the suggestion. _________________ 1980 - 931 |
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Kenodog
Joined: 25 Jun 2003 Posts: 2651 Location: Vancouver,B.C.
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Posted: Thu Mar 08, 2018 5:06 am Post subject: |
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One word for cleaning that shit out, Techron. Can't be beat.
Also, I thought Porsche was re-making those breathers ? I swear they were up on the 'Classics' website not too long ago...
Leigh _________________ 1979 Euro 931, Olive
1981 931, Sabine
1991 Ford Ranger XLT 4x4, Ricky
1996 Ford E-350 ex-FedEx Van
2014 Mazda CX-5 (Kinderwagon)
2019 KTM 790 Adventure
2024 KLX300
2024 KLX140 |
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MOTANUL
Joined: 19 Nov 2018 Posts: 214 Location: ROMANIA BUCHAREST
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Posted: Mon Mar 23, 2020 3:02 am Post subject: |
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I disassembled air/oil separator (purulator).
The front hose had a little residue inside.
The up and back was a little more. The lower-back less residue. In the Purulator there are also small amounts of residue.
_________________ 1980 Porsche 924 Turbo (931) diamond silver metallic/helios blue metallic
sold Porsche 924 NA 1979 |
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MOTANUL
Joined: 19 Nov 2018 Posts: 214 Location: ROMANIA BUCHAREST
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Posted: Thu Mar 26, 2020 4:40 pm Post subject: |
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I have previously written on the forum that the 924 Turbo US models do not bypass the air filter (the hose in the purulator enters the air filter housing in series 1 and series 2).
Question: Is the metal pipe (inside the air filter) in the image below original? (oem for us?)
_________________ 1980 Porsche 924 Turbo (931) diamond silver metallic/helios blue metallic
sold Porsche 924 NA 1979 |
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poor-sche
Joined: 06 Jan 2017 Posts: 80 Location: Los Angeles, CA
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Posted: Fri Mar 27, 2020 4:55 am Post subject: |
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Mine is identical. I would assume it was oem. _________________ 1980 - 931 |
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MOTANUL
Joined: 19 Nov 2018 Posts: 214 Location: ROMANIA BUCHAREST
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Posted: Tue Mar 31, 2020 11:46 pm Post subject: |
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Why are there 2 pipes? I guess the long pipe is set to stop the oil vapor from getting on the air filter.
I do not understand the role of the short pipe. Maybe some clearer pictures would help me figure it out. This picture is from ebay.
Thank you
_________________ 1980 Porsche 924 Turbo (931) diamond silver metallic/helios blue metallic
sold Porsche 924 NA 1979 |
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