Engine Oil in vacuum lines, soot in intake manifold - '94 Cobra

90sblue

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The day started with the goal of replacing a suspect EGR valve. There was a pretty serious amount of soot in the upper intake manifold as well so I decided to remove that and hopefully give a good clean. When I pulled the upper intake, I noticed some oil dripping out of the vacuum lines connected to the back of it. Thoughts on this? Could this be a sign of a bad PCV valve?
Lower intake manifold is also coated in black deposits, so I'm playing with the idea of removing that too.

I'd appreciate some advice on how to clean these, looked at a few online resources already - but what do you guys recommend? Cleaning it while it's off the engine with degreaser or carb cleaner? Running a bunch of seafoam through it? I've got some time before new gaskets arrive so open to ideas.
Thoughts on the oil coming out the vacuum hose and sources of oil that could be getting into the intake manifold?
 
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7991LXnSHO

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OCD wants the intake to be clean inside, but a (light) coating of cooked oil vapor will not be a big deal. It is not worth taking the lower off for. You can clean the lines and upper with a can of carb cleaner.
Yes, the PVC valve is suspect, as is the mesh filter beneath it. You can also check for blow by with compression and leak down tests.
 
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90sblue

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hey guys, thanks for the replies. I did remove the mesh filter below the PCV valve, was really surprised at how easily the grommet and mesh came out, makes me think a previous owner had also replaced them.
once I have the replacement parts I'll slap it back together and check compression.
I'm considering a catch can, hard to tell how bad the oil leak is since I think I'm also leaking oil at the main seal :doh:
 

mostsmooth

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I believe I am getting oil in my vacuum lines as well, sounds like the OP situation (oil, not soot).

There's supposed to be mesh under the PCV valve? is it part of the holder on the inside or outside (underneath)?

Is there a way to check the PCV function?

I happen to have had the PCV out the other day just looking at it, and the plug in the center would rattle around if I shook it, no idea if that's normal or not. I assume that plug in the center would sit there with gravity until the pressure lifted it if need be, so the rattling was normal.

thanks
 

90sblue

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@mostsmooth here's a link to some information on the mesh placement

Pretty sure the rattling is normal, my replacement has arrived and it also rattles (as does the old one I pulled out)
 

mostsmooth

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@mostsmooth here's a link to some information on the mesh placement

Pretty sure the rattling is normal, my replacement has arrived and it also rattles (as does the old one I pulled out)
thanks. reading it now. it says removing the grommet can be a real pain. lol, mine comes out really easy. like if I flipped the intake over it would fall out on its own. seems like that's bad.

Edit: I'm pretty sure I don't have a breather filter either. yikes. on a side note, it reminded me I need to replace the filter on my bike...

Edit 2: hmm, i just went out and checked and sure enough, there's a filter in there. Pic attached. just curious, can i tell from the pic if it is installed upside down? is it even possible to install incorrectly?

thanks
 

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jozsefsz

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It took 25 years to get some carbon deposits, I'd brush where you can reach with some B12 and call it done. Anyone who's had to walnut blast the valves on a modern GDI will agree that the tiny bit of carbon our intakes accumulate over decades doesn't hurt anything. Check back in 20-30 years if you're getting some driveability issues.
 
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90sblue

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@mostsmooth yours installed correctly, there is a top/bottom. yours is also much cleaner than mine...
 

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revhead347

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I've owned these cars forever, and I tell you what, you can replace that PCV valve, grommet, and "filter" every 6 miles, and you are still going to get some oil and soot in the intake. It's just not a very clean system. I even have an oil separator on mine, and oil still ends up in the intake.

Kurt
 
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General karthief

wonder how much it would cost to ship you a pair
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When the engine is running take the oil fill cap off and see if there is any vapors coming out. You can pull the pvc out and hold your finger over the valve opening, this stops the valve from scavenging any vapor first. If you have a lot of blow by it will build up oil in your intake/vacuum lines.
 
Sep 26, 2017
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The day started with the goal of replacing a suspect EGR valve. There was a pretty serious amount of soot in the upper intake manifold as well so I decided to remove that and hopefully give a good clean. When I pulled the upper intake, I noticed some oil dripping out of the vacuum lines connected to the back of it. Thoughts on this? Could this be a sign of a bad PCV valve?
Lower intake manifold is also coated in black deposits, so I'm playing with the idea of removing that too.

I'd appreciate some advice on how to clean these, looked at a few online resources already - but what do you guys recommend? Cleaning it while it's off the engine with degreaser or carb cleaner? Running a bunch of seafoam through it? I've got some time before new gaskets arrive so open to ideas.
Thoughts on the oil coming out the vacuum hose and sources of oil that could be getting into the intake manifold?
Simple reversion is normal. Reverse flow thru the head. Valve overlap, Hotrod camshafts all good. Can be cleaned but why? Use ford carb foam and run thru the plate. replace the spark plugs after. Might just as well clean the injectors with the ford rail cleaner stuff too. They have pressurized cans or you can use an injector cleaner apparatus and use the cheaper stuff in the can. Carb cleaner foam disconnect the maf it should run well enough to get the sauce thru it. Send it
Love those Cobras
 
Sep 26, 2017
37
4
18
61
Simple reversion is normal. Reverse flow thru the head. Valve overlap, Hotrod camshafts all good. Can be cleaned but why? Use ford carb foam and run thru the plate. replace the spark plugs after. Might just as well clean the injectors with the ford rail cleaner stuff too. They have pressurized cans or you can use an injector cleaner apparatus and use the cheaper stuff in the can. Carb cleaner foam disconnect the maf it should run well enough to get the sauce thru it. Send it
Love those Cobras
Those 46es are hell on the EGR port The valves themselves seem to never plug up. Funny thing they run better with a clean egr port
 
Sep 26, 2017
37
4
18
61
The day started with the goal of replacing a suspect EGR valve. There was a pretty serious amount of soot in the upper intake manifold as well so I decided to remove that and hopefully give a good clean. When I pulled the upper intake, I noticed some oil dripping out of the vacuum lines connected to the back of it. Thoughts on this? Could this be a sign of a bad PCV valve?
Lower intake manifold is also coated in black deposits, so I'm playing with the idea of removing that too.

I'd appreciate some advice on how to clean these, looked at a few online resources already - but what do you guys recommend? Cleaning it while it's off the engine with degreaser or carb cleaner? Running a bunch of seafoam through it? I've got some time before new gaskets arrive so open to ideas.
Thoughts on the oil coming out the vacuum hose and sources of oil that could be getting into the intake manifold?
Oil in the vacuum lines is a bit of a problem. Common almost normal for your Cobra with all the valve overlap. Check the PCV and your altitude calibration. You may need a swap or install two pcv valves into the system. SVO's were hell on this. Nothing that ran on vacuum worked well. Check out what Mercedes does to control crankcase vapor with four rotating centrifugal oil separators. Install a crank evap setup if you're going racing