: PCV oil catch can, intake sludge

03-10-10, 06:21 PM
Upon inspection of the TB, I noticed the inside of the intake manifold is full of oily sludge residue. It lines the walls. Knowing that the N* consumes oil, I wonder how much is being drawn in from the crankcase, PCV system.

Back in the day we used to use crankcase oil catch cans. I wonder if it would be okay to use on the N* engine.

Here is a link describing what they are and what they do.

I built my own for my service van out of a canning jar and some fittings from Home Depot for about $10. Doesn't look as pretty as the $100 though.

Would the lack of oil fumes hurt anything? Essentially the oil fumes are being condensed in the can but the air can still flow into the intake manifold.
Any suggestions would be appreciated. You just empty the container when half full. (recycle it of course, but not back into your engine)



03-11-10, 12:28 PM
If you can come up with a place to mount one, there's no reason not to experiment. The 2001 (?)+ engines use a fixed orifice and that doesn't seem to suffer from quite as much oil carryover in the PCV system as the rattle valve types.

Keep your airflow as close to stock as possible because that PCV is calculated into MAF and fuel/air ratios.

03-12-10, 01:20 PM
I put on a crude PCV catch tank for the purposes of the trial. I ran fuel line hose (for fuel injection) from the PCV valve to the catch. The reason I used fuel line is that it is thick, and will stand up to oil/fuel. I want it thick to help insulate the line to oil does not condense in the hose.

Though there are two valve cover vents, only the one with the PCV valve needs this modification. The other valve cover vent is for air intake. It flows into one valve cover and out the other.
Here is the routing on a 99 DeVille.
<a href="http://s656.photobucket.com/albums/uu289/cmobile/Cadillac/?action=view&current=PCVroutingmanifold.jpg" target="_blank"><img src="http://i656.photobucket.com/albums/uu289/cmobile/Cadillac/PCVroutingmanifold.jpg" border="0" alt="PCV"></a>

closeup of PCV Valve
<a href="http://s656.photobucket.com/albums/uu289/cmobile/Cadillac/?action=view&current=PCVvalve.jpg" target="_blank"><img src="http://i656.photobucket.com/albums/uu289/cmobile/Cadillac/PCVvalve.jpg" border="0" alt="PCV"></a>

overview with vanity cover installed.
<a href="http://s656.photobucket.com/albums/uu289/cmobile/Cadillac/?action=view&current=front.jpg" target="_blank"><img src="http://i656.photobucket.com/albums/uu289/cmobile/Cadillac/front.jpg" border="0" alt="PCV"></a>

Closeup of catch can with oil drip. after 5 minutes of running at temp.
<a href="http://s656.photobucket.com/albums/uu289/cmobile/Cadillac/?action=view&current=Catchcaninaction.jpg" target="_blank"><img src="http://i656.photobucket.com/albums/uu289/cmobile/Cadillac/Catchcaninaction.jpg" border="0" alt="PCV"></a>

03-12-10, 08:18 PM
The oil catch can is installed in the PVC system. It comes from the PCV valve to the front of the engine bay into the tank, then back to the the manifold vacuum. I ran it to the front because I believe the the cooler air will help to condense the oil fumes.

Put about 100 miles today and I have a few drops of oil.

The catch can is crude but it suits the need for this trial test, to determine any benefits.

I used fuel hose which will help insulate the line-set to reduce oil condensation within the lines. It is one size bigger than the plastic lines and slips right over negating the need for extra fittings.

Will keep you updated.

03-17-10, 10:39 AM
I installed the catch can last week. So far I have driven about 200 miles. I have about 1/4 oz of oil in the jar.

I used a crude catch can initially to verify the effectiveness before spending any real money. So far it seems to be working.

The OEM PCV system air flow comes from the TB into the "front" valve cover, through the crankcase an out the other rear valve cover through the PCV valve, then into the intake manifold. The hoses attach inline between the PCV valve and intake manifold. The catch can is installed at the front of the engine compartment to ensure the catch can was cool and would aid in condensing oil fumes.

Going on a 1400 mile trip today. I'll keep you updated.


03-17-10, 04:09 PM
This is really interesting. Keep us updated! :food-snacking:

03-17-10, 08:29 PM
Yeah - very interesting!

03-17-10, 08:41 PM
Out of curiosity, how many people add oil until it is at the top mark on the dipstick? I read in some GM document that the top mark is actually an overfilled condition and the excess oil will be scavenged by the PCV system. I want to find the person that designed that dipstick!

Regardless, my oil consumption dropped when I stopped filling it to the top mark on the dipstick.

03-17-10, 09:49 PM
I used to fill to the top and add a quart when it hit the add mark - now I fill to the half way mark and add 1/2 quart when it drops to the add mark, or add a quart when 1/ quart below add. Frankly, I never noticed any difference in oil consumption, nor does my oil consumption of a quart every 1,500-2000 miles on every Northstar engine car I own or have owned (7 of them) bother or concern me in the least.

03-18-10, 08:23 AM
This particular aspect of Northstar dipstick operation (overfilling) is like

as it has been discussed to ad nauseum in CF for years. The info is contained in many, many posts in here and up in Seville and Deville.

03-18-10, 02:48 PM
Yeah - I know what you're sayin' Sub - it's old hat to us, but there are always new people cycling through that it's a brand new concept. It's like the another current thread where WOT is being discussed - some people have no idea what it is, how to do it, or what it achieves. I hate to say it, but I think a lot of members get the wrong idea and use the name "WOT" to beat the p_ss out of their car, which is really not the same thing. Anyway, I think if those of us that have been here for awhile try to remember the first time we learned about WOT and oil usage and motor mounts and head gasket problems, etc., we will find it more palatable to keep reading about and answering the same questions over and over.

03-18-10, 03:57 PM
Granted ............. but sometimes it would be simpler to ask people to do some homework rather than type the same thing over again every 10 days. Even other members, most of who know a heck of a lot about Northstars, get a bit snarky once in a while when someone asks the same question that was answered last evening.

I'm not bitching - but this set of Forums is like Webster's Unabridged: very large, but the information is in there to be found. All of it.

......back to the oil catch can....... I did some snooping this morning, prompted by cmobile's pictures. My car has the fixed orifice PCV rather than the rattle valve. The inside of the PCV vacuum line - from the rear cam cover to the inner center of the intake manifold recess - is essentially dry and clean. With the engine idling there is significant vacuum (therefore, airflow) in that line. My engine gets over 4,000 miles to the quart of 5W-30 Pennzoil synthetic. Which begs the question: Does the orifice type of PCV vacuum metering contribute to lessened oil consumption ? What say you, 2000+ Northstar owners ???

Note that both types of system source clean air from just upstream of the butterfly, at the non-vacuum side of the TB.

and, you'll notice that the earlier, pre-2000, PCV vacuum (and therefore, vapors) is ported to the throttlebody, right after the butterfly. Does this somehow contribute to throttlebody dirt and grime ? - my TB generally stays very clean. Very clean.

03-18-10, 04:12 PM
Granted ............. but sometimes it would be simpler to ask people to do some homework rather than type the same thing over again every 10 days. Even other members, most of who know a heck of a lot about Northstars, get a bit snarky once in a while when someone asks the same question that was answered last evening.

I'm not bitching - but this set of Forums is like Webster's Unabridged: very large, but the information is in there to be found. All of it.

Yeah - I know, Sub, and I agree with you, and I am not criticizing you. I'm tired of seeing the same questions all the time, but let's face it - it's not going to change. I'm just suggesting that it might help all of us old guys to be less crotchety if we try to remember when we were the newbies.

03-18-10, 04:21 PM
Fer the luvva' Pete, who the devil is crotchety ???

03-18-10, 05:46 PM

Which begs the question: Does the orifice type of PCV vacuum metering contribute to lessened oil consumption ? What say you, 2000+ Northstar owners ???
Good question and it make one wonder why they switched to that system, but I have no answer. Mine does not seem to get very dirty, but then again, I clean mine every spring.

03-18-10, 07:40 PM
Fer the luvva' Pete, who the devil is crotchety ???

Me, a lot of the time!

But, I am trying to be better...

03-19-10, 11:57 PM
Sorry for the multiple posts initially, it took several days to post and I thought I was doing something wrong.

I put on 800 freeway miles in the past few days there is only about an ounce of oil. though the oil does not smell like oil. Maybe a hint of fuel? not sure.

Initially it was light brown/cream colored indicating water. This was in Colorado though. Here in Phoenix, it is dark brown now, especially after the 800 mile trip.

I fill the oil to the half way mark on the dipstick and use Rotella T-5 10W-30 synthetic blend. I did WOT treatment prior to installing catch can.

I cleaned the TB and intake manifold (as much as I could w/o removing it before the trip.

I think I will continue to use the "catch can" in the hopes it will help keep my intake system cleaner. I figure 10W-30 oil doesn't burn like gas.

Love the gas mileage these cars get. 27.4 MPG driving maybe 85 MPH?
How cool is that!!!


03-20-10, 11:59 AM
So far, everything you've seen is perfect.

A city driven car will normally exhibit a LOT of condensation in the valve covers and oil pan - that's the coffee cream colored snot being removed by the PCV. A highway car will exhibit fairly pure oil vapor -the entire inside of that engine looks like a giant high speed washing machine full of oil at highway speeds, so some of that hot oil gets purged as mist.

ROTELLA T-5 is damn good oil. Because it's certified Fleet and Diesel (CF, CF-2, CC, CD ???) your engine will love it.

johnny kannapo
10-03-10, 02:57 PM
Beating this dead horse again.

I am looking into the PCV catch can Idea. Although not a problem 3000 to 3500 mi per qt.

I want to address the dirty intake deposits and see if I can reduce the gunk accumulation. & prevent/reduce the need for the" chemical ring cleaning proceedure" or piston knock that occurs until you go beat on it and it goes away.

I am more curious about the front VC 1/2"vent tube contributing to this problem.

Would using the same sort of device on the front cover vent help?

Although pathetically dirty rear of the throttle plate, the front side of the TB was very clean.

I have already fabricated a crude device mostly sourced at Home Depot for less than $20 & only slightly more advanced than the OP, cmobile.

http://i826.photobucket.com/albums/zz183/billytheshoe/th_100_1144.jpg (http://s826.photobucket.com/albums/zz183/billytheshoe/?action=view&current=100_1144.jpg)
http://i826.photobucket.com/albums/zz183/billytheshoe/th_100_1145.jpg (http://s826.photobucket.com/albums/zz183/billytheshoe/?action=view&current=100_1145.jpg)
http://i826.photobucket.com/albums/zz183/billytheshoe/th_100_1143.jpg (http://s826.photobucket.com/albums/zz183/billytheshoe/?action=view&current=100_1143.jpg)

10-03-10, 06:29 PM
In your engine the front valve cover pipe is the "clean air" source, from the non-vacuum side of the throttle butterfly. The rear valve cover pipe goes to the vacuum side of the throttlebody, and unfortunately for the design that's exactly where all the crankcase snot and nasties wind up. The 2000+ "dirty air" pipe goes into the intake manifold, depending on year, well away from the throttle butterfly and bore, so the entire TB section stays a lot cleaner.

In either arrangement the PCV valve or orifice is part of the calibrated intake manifold air supply, so, to change the clean air supply to either a vacuum or dead end would cause mixture problems as well as emissions codes.

There would be nothing wrong with an owner moving the dirty air pipe to a central location in the intake manifold plenum - not in a single intake runner - in the main void space. A simple threaded nipple, rubber vacuum hose, and some MarineTex epoxy putty would do the trick. This afternoon project would guarantee you a clean TB for years.

johnny kannapo
10-03-10, 07:08 PM
I am understanding that sub, I am going to go ahead with the PCV trap and see how much that system will collect.

I understand that the PCV is calibrated and don't intend to change the flow of that vent circuit.

I know the PCV is calibrated for CFM and just want to keep things clean and have done some homework on the subject.

I just was unclear on the front VC vent side and if it can become a vacuum draw. I can see the glued in baffle right in the fill hole.

Ultimately if all worked well with the baffle/chambers that are glued in the valve cover worked without oil intrusion there would be no problem. & I may have less consumption. I may just go ahead & pull the VC's and take a peek at whats going on under there. AJxtcman had pics up to example the problem.