Busting my own MYTH - oil catch can

[Maximus Gladius]

(21 JTR, 96k kms TL, second engine has just over 60k kms)
So, I’ve had a long standing belief that if I couldn’t “feel” air blowing out the oil fill cap while engine running, my rings were seated perfectly and didn’t have blowby and thereby, didn’t need an oil catch can. WRONG!

I installed one just for fun a couple weeks back (1500 kms) because I ordered one over a year ago and it was just sitting in the garage and I just never thought I needed to install it.

So about a month ago, I changed out my plugs at only 60k kms and they all showed oil burn on them. #5 plug was faulty and caused a misfire. They smelled like oil and #6 was wet oily. This is where things get technical because I can “see” and feel the operation of the positive and negative pressure from the PCV (passenger side rear engine location and MUA (make up fresh air) on the driver’s side rear engine location)

This is where I’m super confused. To be quick, catch can has oil in it.
1. I can feel no air blowing out my oil fill cap when engine is running.
2. PCV is replaced when I replaced all my plugs. There is a strong suction of air being drawn through the PCV via the draw from intake manifold after the throttle body. If the hose is pulled there, the suction is massive and the engine doesn’t want to run.
3. The MUA tube that’s located right after the air box and enters the intake air tube has very little suction that’s providing fresh air to the engine on the drivers side rear engine.

So this is where I’m confused and I’m trying to figure out all the different amounts of air flow between the no air blowing or sucking at the oil fill cap, the huge amount of air circulating at the PCV, upper intake manifold and crank case and near zero air being sucked in at the MUA tube.

So to be clear, I have never sat in a classroom to learn mechanics stuff. I’ve only done my own wrenching which has been more than normal for most “non classroom learned” folks.

My thinking also when I’ve done my oil changes and find the level down 1/4-1/2 litre is that this oil has made it through the rings and I’ve burned it off. Now, I see consumption through the PCV as I look at the oil in the catch can.

The wet oily #6 plug now makes sense in that as the droplets of oil are entering the intake manifold, the rush of intake air through the manifold is just forcing that oil to #6. The other plugs that just show oil burn but not wet is maybe those droplets go to the other cylinders at idle ?? Perhaps.

Anyway, I’m glad I installed the can. I want my plugs to burn cleaner and the can shows me I just might accomplish this.

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[Scott L]

Looks to me like your #1 and #5 electrodes are toast or is that just the picture? No idea about the catch can but afaik it shouldn’t be needed on a N/A engine yet here it is and it and looks like it’s catching at least some oil.

 

[Maximus Gladius]

Looks to me like your #1 and #5 electrodes are toast or is that just the picture? No idea about the catch can but afaik it shouldn’t be needed on a N/A engine yet here it is and it and looks like it’s catching at least some oil.

#5 is definitely damaged. Also, the spread of the gap on #1 through 4 were same to marginally different to some very small degree. Right around .44. #5 was noticeable @.50 BUT #6 was even spread more to .55. That could also explain why #6 is wet.

 

[hjdca]

Some more information for you...

I started getting EGR errors around 60K miles, and I replaced the EGR and the EGR sensor. The sensor especially had some carbon crud on it. My PCV line did have oil in it. I was not burning oil, about 1/4 of a quart every 3.5K or 4K miles. I did install the Mishimoto catch can, and i really like it. Especially, how easy it is to drain the can with the built in drain hose. I get a 1 or 2 ounces of oil every 1500 miles or so. There is a TSB out on our PCV valve for carbon build up. There is an updated part number for a new PCV. You might want to try that. For some reason this new PCV is $120 vs. the old PCV being $30.... lol... Note: I am assuming the new PCV will have a tighter spring which in turn will create a little more crank pressure before releasing pressure to the hose... I decided to stick with the old PCV and go with the catch can, since, I do not want to suddently get oil leaks from my gaskets, ie. due to more crank case pressure... ... I am attaching the TSB with the Part numbers, so, you can read it.

 

[Maximus Gladius]

Some more information for you...

I started getting EGR errors around 60K miles, and I replaced the EGR and the EGR sensor. The sensor especially had some carbon crud on it. My PCV line did have oil in it. I was not burning oil, about 1/4 of a quart every 3.5K or 4K miles. I did install the Mishimoto catch can, and i really like it. Especially, how easy it is to drain the can with the built in drain hose. I get a 1 or 2 ounces of oil every 1500 miles or so. There is a TSB out on our PCV valve for carbon build up. There is an updated part number for a new PCV. You might want to try that. For some reason this new PCV is $120 vs. the old PCV being $30.... lol... Note: I am assuming the new PCV will have a tighter spring which in turn will create a little more crank pressure before releasing pressure to the hose... I decided to stick with the old PCV and go with the catch can, since, I do not want to suddently get oil leaks from my gaskets, ie. due to more crank case pressure... ... I am attaching the TSB with the Part numbers, so, you can read it.

I kept the new PCV box with the part # so I’ll confirm the TSB # to that. Also, when I had the first engine replaced (manufactured in 11/20), I was told I was getting an “upgraded engine” (installed October 2022) and it would deal with the misfire/cam/lifters issues. Also the tsb# ? that speaks of the “upgraded engine” just mentions the engine holds 5 litres, NOT 6 like the first gen engines.

Here’s the thing, my old engine held 5L. The new engine or 2nd gen engine also holds 5 litres. So my first and second engine were both second gen engines.

Before I replaced my spark plugs, I talked with my service manager about this “new” PCV valve being different than the “first gen” engines. He and the shop forman both said my old engine made in 11/20 and the second engine installed 10/22 are both the same 2nd gen and would have the same PCV valve. I know I paid over $100 for that valve.

 

[hjdca]

I kept the new PCV box with the part # so I’ll confirm the TSB # to that. Also, when I had the first engine replaced (manufactured in 11/20), I was told I was getting an “upgraded engine” (installed October 2022) and it would deal with the misfire/cam/lifters issues. Also the tsb# ? that speaks of the “upgraded engine” just mentions the engine holds 5 litres, NOT 6 like the first gen engines.

Here’s the thing, my old engine held 5L. The new engine or 2nd gen engine also holds 5 litres. So my first and second engine were both second gen engines.

Before I replaced my spark plugs, I talked with my service manager about this “new” PCV valve being different than the “first gen” engines. He and the shop forman both said my old engine made in 11/20 and the second engine installed 10/22 are both the same 2nd gen and would have the same PCV valve. I know I paid over $100 for that valve.

My Gladiator build was 2019.

1. My passenger side intake cam lobes and rockers wore out on the high lift mode. I noticed the new replacement cam and rockers had "AD" at the end of the Part numbers instead of the "AA" that my originals had. So, this may be the upgrade they are talking about.

2. All the Gladiator 3.6 gas engines have held 5L of oil.

3. yes, just check the Part number on your PCV valve to see if it is the new one or the old one.

 

[HorsesRear]

I have had more vehicles than I can count and I never had a catch can on any of them. I am unsure what makes this engine so unique that it requires a catch can. I never even heard of them until I joined this forum.

 

[willys 41]

Some more information for you...

I started getting EGR errors around 60K miles, and I replaced the EGR and the EGR sensor. The sensor especially had some carbon crud on it. My PCV line did have oil in it. I was not burning oil, about 1/4 of a quart every 3.5K or 4K miles. I did install the Mishimoto catch can, and i really like it. Especially, how easy it is to drain the can with the built in drain hose. I get a 1 or 2 ounces of oil every 1500 miles or so. There is a TSB out on our PCV valve for carbon build up. There is an updated part number for a new PCV. You might want to try that. For some reason this new PCV is $120 vs. the old PCV being $30.... lol... Note: I am assuming the new PCV will have a tighter spring which in turn will create a little more crank pressure before releasing pressure to the hose... I decided to stick with the old PCV and go with the catch can, since, I do not want to suddently get oil leaks from my gaskets, ie. due to more crank case pressure... ... I am attaching the TSB with the Part numbers, so, you can read it.

I have an UPR oil catch can with a 4ft 1/2in. drain hose keeping the oil out of the can and in the drain hose.
I have always collected the oil at 1000 miles for comparison.
After in stalling the updated PCV valve there was no difference in the amount of oil the can collected.
Before and after the updated PCV valve I collected the same amount of oil.

 

[Lunentucker]

That's about how much liquid I get every 1000 miles as well.
It's not a lot when amortized over the run time and revolutions of the engine over that much distance, but what's it going to hurt to get it out of the intake and keep the combustion chambers and valves cleaner?
Nothing as far as I ca see.

On the image above comparing the new and the old PCV valves - I watched a video on replacing the valves some time ago.
All of the used ones look like that, and all of the new ones look like that. Whether they're the new part number or the old one. They go on with a small hole in them and come out with a larger one.
Kind of like prison.

 

[willys 41]

That's about how much liquid I get every 1000 miles as well.
It's not a lot when amortized over the run time and revolutions of the engine over that much distance, but what's it going to hurt to get it out of the intake and keep the combustion chambers and valves cleaner?
Nothing as far as I ca see.

On the image above comparing the new and the old PCV valves - I watched a video on replacing the valves some time ago.
All of the used ones look like that, and all of the new ones look like that. Whether they're the new part number or the old one. They go on with a small hole in them and come out with a larger one.
Kind of like prison.

The biggest improvement and the reason I tried a catch was the supper bad spark knock I was getting.
I first noticed it pulling a steep hill in 4L at about 1500 RPMs.
I was running 91 octant and at about 4000ft. and could not believe that what I was hearing was spark knock.
After some research I had read that the 3.6 can and will have severe ping / spark knock.
I had also read that blow-by gasses can degrade the octane levels and adding a catch can can help.
I was extremely skeptical to say the least.
After installing the catch can NO more ping / spark knock. Not one ping.
So I put one on my wife's Rubicon and just installed one on my new 2020 F250 6.2 gas.

 

[Hootbro]

I have an UPR oil catch can with a 4ft 1/2in. drain hose keeping the oil out of the can and in the drain hose.
I have always collected the oil at 1000 miles for comparison.
After in stalling the updated PCV valve there was no difference in the amount of oil the can collected.
Before and after the updated PCV valve I collected the same amount of oil.

Been two years since that TSB came out and AFAIK, MOPAR parts has yet to put that TSB P/N PCV valve in the system as a superseding part. To date, nobody has explain what makes that TSB PCV valve different or special other than costing way more.

 

[hjdca]

Been two years since that TSB came out and AFAIK, MOPAR parts has yet to put that TSB P/N PCV valve in the system as a superseding part. To date, nobody has explain what makes that TSB PCV valve different or special other than costing way more.

yeah, thanks, good point, I saw that, and that is why I put in a little more money and got the catch can and kept my original PCV. Now I know exactly how much oil was going back to my intake. I also was thinking they may not supersede the old PCV because this new one may have a tighter spring, thus, increasing the case pressure (ie. New oil Leaks ?). So, the dealer may just use it if you have a carbon build up problem. Who knows, it’s just conjecture on my part.

 

[Rusty PW]

I have had more vehicles than I can count and I never had a catch can on any of them. I am unsure what makes this engine so unique that it requires a catch can. I never even heard of them until I joined this forum.

Catch cans have been around for a long time. I had them on my 08 5.7 Hemi Power Wagon, 13 5.7 Hemi Grand Cherokee, and 2 on my twin turbo 3.7 Nismo.

 

[ShadowsPapa]

Been two years since that TSB came out and AFAIK, MOPAR parts has yet to put that TSB P/N PCV valve in the system as a superseding part. To date, nobody has explain what makes that TSB PCV valve different or special other than costing way more.

People need to ignore that seal..... like already said. It's misleading.

To know the differences between the two PCV valves, you'd need to know the exact shape of the shuttle valve inside and the spring strength, to start with.
Each PCV is rated as to how may CFM it flows at xx inches of vacuum.
And that's a matter of the strength of the spring and the shape of the valve inside - the taper it has. XX inches of vacuum will pull against the spring xx amount. The valve inside has a tapered shape.
They are actually engineered based on the amount of air that needs to be evacuated from the crankcase and the typical intake manifold vacuum at various loads and RPMs.

So you'd apply a certain amount of vacuum to move the valve inside to a specific position and measure the flow. That's what they change to vary PCV valves for various engines - how many CFM of flow at a given amount of vacuum applied. And because the valve inside is tapered, it means they can keep the flow the same at one vacuum level and increase or decrease it at another.
It's a big deal with modifying engines.
(PCV valves for turbo engines are very different)

I went over 7,000 miles on my last oil change - it wasn't even yet half-way down on the add/full part of the stick, and to this day, has no ping at all. (I'd say maybe 1/3 of the way down in that time)

And seeing comments above - all Gladiator 3.6s take 5 quarts of oil. That has never varied for the JT.

 

[Maximus Gladius]

Some more information for you...

I started getting EGR errors around 60K miles, and I replaced the EGR and the EGR sensor. The sensor especially had some carbon crud on it. My PCV line did have oil in it. I was not burning oil, about 1/4 of a quart every 3.5K or 4K miles. I did install the Mishimoto catch can, and i really like it. Especially, how easy it is to drain the can with the built in drain hose. I get a 1 or 2 ounces of oil every 1500 miles or so. There is a TSB out on our PCV valve for carbon build up. There is an updated part number for a new PCV. You might want to try that. For some reason this new PCV is $120 vs. the old PCV being $30.... lol... Note: I am assuming the new PCV will have a tighter spring which in turn will create a little more crank pressure before releasing pressure to the hose... I decided to stick with the old PCV and go with the catch can, since, I do not want to suddently get oil leaks from my gaskets, ie. due to more crank case pressure... ... I am attaching the TSB with the Part numbers, so, you can read it.

I checked the number stamped into the old PCV and also the number on the box of the new one and compared it to the TSB sheet you provided.

Both PCV’s have the same number which end with “AC”, this supersedes the TSB number ending with “AA”.

We’ve also seen photos posted of the seal side of two different PCV’s. The old PCV seal hole will be larger than the new one. This is not an indicator to say “the PCV is made differently”. Once the new PCV is slipped on over the “tube” (I don’t know what to call it), the small hole becomes larger. The smaller hole seal made to slip over the larger sized tube is just to ensure seal.

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