6.6 - Catch Can - Final Answer

6.6HD · February 18, 2021

I will make this very long story as short as possible.

Less than 10K. Many trips to dealer due to engine light and running rough and also going into reduced power mode.

Finally able to identify bad injector in one of the cylinders. They replaced it. When I picked up the truck, the mechanic showed me the injector. Reminder... less than 10k on the motor. There was already coking and carbon deposits on it.

I went on to ask the mechanic if the intake had oil in it. He said the intake was coated in oil. I said, "So, this engine will benefit from a catch can...?". The mechanic said, "It will for sure".

I had one on my '17 1500 that I emptied regularly. I have yet to put it on my 2500. After my conversation with the mechanic, I will be putting that can on this truck ASAP.

Will it void your warranty is the obvious next question... it depends on the dealership. There is no pat answer to this. So, if your worried about it... and your truck is still under factory warranty... ask your dealership... If they say it does then go to another dealership. The one I used could care less that I had a can on my 1500.

No more discussion needed guys and gals.

mrjulian416 · February 18, 2021

The injector failed due to the coking? Or was it coked up because it wasn't operating correctly?

6.6HD · February 18, 2021

Great question. One I did not think to ask... and, frankly, I dont know if its possible to determine that.

Regardless... For me, the can is going on due to the intake being coated in oil. The mechanic was very clear that it was "coated" and that a can would mitigate it. That is enough reason for me and I am not concerned about the warranty because, with this truck, its an easy on and off (easier than the 1500). So, if needed, I can take the can off before going to the dealership.

Gene Steffens · February 18, 2021

I still do not understand “catch can” what is it, and why would you think you need it. I’ve drove GM products ever since I’ve been driving, never heard the term catch can, most of my GM vehicles were pickups, probably the best one I ever had was my 1996 Chevy 1 ton dully with the 454 motor, pulling a fairly large fifth wheel(over 12,000 lbs) , pulled it all over this USA I got 12 mpg whether I was pulling or just running dry, I even used it as my daily driver, I never experienced any oil leakage or plug problems, it wasn’t direct injection but was enjected thru throttle body, I drove this truck to at least 185,000 miles, sold it to a lady in Texas and she had it tore. Down and completely checked by a GM mechanic, he told her who ever owned this truck took very good care of it, he found no, or very little wear in the cylinder area, and crank shaft, and cam area, said it was like new inside, like it said no oil leakage or blow by anywhere. So I don’t know the term catch can

It's Tim · February 18, 2021

53 minutes ago, 6.6HD said:

I will make this very long story as short as possible.

Less than 10K. Many trips to dealer due to engine light and running rough and also going into reduced power mode.

Finally able to identify bad injector in one of the cylinders. They replaced it. When I picked up the truck, the mechanic showed me the injector. Reminder... less than 10k on the motor. There was already coking and carbon deposits on it.

I went on to ask the mechanic if the intake had oil in it. He said the intake was coated in oil. I said, "So, this engine will benefit from a catch can...?". The mechanic said, "It will for sure".

I had one on my '17 1500 that I emptied regularly. I have yet to put it on my 2500. After my conversation with the mechanic, I will be putting that can on this truck ASAP.

Will it void your warranty is the obvious next question... it depends on the dealership. There is no pat answer to this. So, if your worried about it... and your truck is still under factory warranty... ask your dealership... If they say it does then go to another dealership. The one I used could care less that I had a can on my 1500.

No more discussion needed guys and gals.

So... this dudes an "expert" in "catch cans" but failed to notice the engine was only running on 7 cylinders multiple times? Probably time to find a different mechanic and not waste money on a snake oil "catch can".

It's Tim · February 18, 2021

4 minutes ago, Gene Steffens said:

I still do not understand “catch can” what is it, and why would you think you need it. I’ve drove GM products ever since I’ve been driving, never heard the term catch can, most of my GM vehicles were pickups, probably the best one I ever had was my 1996 Chevy 1 ton dully with the 454 motor, pulling a fairly large fifth wheel(over 12,000 lbs) , pulled it all over this USA I got 12 mpg whether I was pulling or just running dry, I even used it as my daily driver, I never experienced any oil leakage or plug problems, it wasn’t direct injection but was enjected thru throttle body, I drove this truck to at least 185,000 miles, sold it to a lady in Texas and she had it tore. Down and completely checked by a GM mechanic, he told her who ever owned this truck took very good care of it, he found no, or very little wear in the cylinder area, and crank shaft, and cam area, said it was like new inside, like it said no oil leakage or blow by anywhere. So I don’t know the term catch can

Peeps are worried to death about a little engine oil in the intake manifold but seemly could less that their arteries are almost plugged solid from fat food.

6.6HD · February 18, 2021

2 hours ago, It's Tim said:

So... this dudes an "expert" in "catch cans" but failed to notice the engine was only running on 7 cylinders multiple times? Probably time to find a different mechanic and not waste money on a snake oil "catch can".

Dang... whats with all the sour grapes?? I didn't say I was an expert on anything. ...and of course I noticed when the one cylinder went nuts... it went into the shop each and every time it dropped.

I think someone woke up on the wrong side of the bed today. Or, perhaps you got your weewee caught in your tail pipe this morning.

...dang dude... relax and be nice. No need for such talk. We are all here to pass on information about our trucks.

6.6HD · February 18, 2021

2 hours ago, Gene Steffens said:

I still do not understand “catch can” what is it, and why would you think you need it. I’ve drove GM products ever since I’ve been driving, never heard the term catch can, most of my GM vehicles were pickups, probably the best one I ever had was my 1996 Chevy 1 ton dully with the 454 motor, pulling a fairly large fifth wheel(over 12,000 lbs) , pulled it all over this USA I got 12 mpg whether I was pulling or just running dry, I even used it as my daily driver, I never experienced any oil leakage or plug problems, it wasn’t direct injection but was enjected thru throttle body, I drove this truck to at least 185,000 miles, sold it to a lady in Texas and she had it tore. Down and completely checked by a GM mechanic, he told her who ever owned this truck took very good care of it, he found no, or very little wear in the cylinder area, and crank shaft, and cam area, said it was like new inside, like it said no oil leakage or blow by anywhere. So I don’t know the term catch can

Catch can is much like a Oil/Water separator.

A catch can is only relevant for a DI engine. There is so much info out there... do a bit of googling for more info.

Edited February 18, 2021 by 6.6HD

Colossus · February 19, 2021

8 hours ago, 6.6HD said:

Finally able to identify bad injector in one of the cylinders. They replaced it. When I picked up the truck, the mechanic showed me the injector. Reminder... less than 10k on the motor. There was already coking and carbon deposits on it.

I went on to ask the mechanic if the intake had oil in it. He said the intake was coated in oil. I said, "So, this engine will benefit from a catch can...?". The mechanic said, "It will for sure".

10,000 miles? Cylinders, valves, and injectors have carbon deposits on them in as little as 3000 miles. It's a sad side affect of direct injection engines. Same with the oil in the intake. Very important to run good top tier fuel, as well as additives to address the carbon build up. This is the case in all modern direct injection engines. Regardless of manufacturer.

6.6HD · February 19, 2021

12 hours ago, Colossus said:

10,000 miles? Cylinders, valves, and injectors have carbon deposits on them in as little as 3000 miles. It's a sad side affect of direct injection engines. Same with the oil in the intake. Very important to run good top tier fuel, as well as additives to address the carbon build up. This is the case in all modern direct injection engines. Regardless of manufacturer.

I am so glad you mentioned top tier fuel! The mechanic said the same thing. I am a bit embarrassed that I didn't know what the heck he was talking about.

Well, I knew some companies had better gas than others... I knew some companies had more additives than others... But, I didn't know anything about Top Tier Fuel. I looked into the matter once I got home and sure enough... So, anyway.. learn something new every day... Lucky for me, Costco is on the list and there is right one right down the road from me.

So, to put the matter of a catch can to bed for once and for all (there are endless threads about the subject out there), and since the inception of the 6.6 there has been lots of questions about whether its built in oil separator is enough, I think I can safely say:

1. Almost any DI engine can benefit from a can.

2. The warranty issue cant be answered in a black and white way. You must figure that one out for yourself.

3. Almost every DI engine should be fueled with a top tier fuel if you can.

By the way, I had a can on my '17 1500 and still have two full mason jars filled with oil that I dumped from it over three years. I am a big believer in them. My quest was about this new 6.6. There is a lot of marketing material out there stating that there is a built in oil separator and they spent a lot of time and engineering trying to solve the issue.

For me, case closed.

GMC4Zee · February 19, 2021

One word of caution about catch cans, they dont perform well in cold climates. They may catch water vapor but not as efficient with catching oil. I dont have a definitive answer on what temp they become less effective but if I were to venture a guess it would be below freezing. This info was learned from another GM forum as I was doing research on this too. I agree with using top tier gas and additives as well as the correct recommended oil and change intervals per the manual. It was also said that eliminating the PVC closed system would work although that will definitely void your warranty.

Davew277 · December 16, 2022

Deleted.

Edited December 16, 2022 by Davew277

GMC4Zee · March 21, 2023

So to answer the other question of what it does, its part of the PCV (positive crankcase ventilation) system. All motors create pressure in the motor down where the oil sits and crank is moving. This pressure makes its way into the valve area. Older engines just used a filter atop the valve cover and vented vapors to the air. Well the EPA does not like this so the PCV was invented and it routes the vapor back into the intake manifold via a oneway valve (PCV)to be burned. So the vapor contains oil and water vapors. These vapors if in too much quantity can coat the intake manifold and are sucked into the engine to be reburned. The will coat anything in the path usually injectors or plugs. Since the plugs fire hot, they kind of self clean but not the injectors. So a catch can is installed inline between the valve cover and intake. It has a screen filter which traps the oil and water which cools and pools up in the can instead of getting sucked back into the engine. Is it 100% effective? No but it helps. So it "catches" the oil and water vapors. It will have a removable bottom can or valve that you empty as often as needed. Now I am not an expert and may have some info wrong but that is the gist of how and why its needed. Hope it help those who asked. I used one on my 2009 G8 and it was helpful keeping the intake cleaner.

lsttype · March 22, 2023

So should we be using seafoam to clean the top end from time to time?

Jettech1 · March 22, 2023

10 minutes ago, lsttype said:

So should we be using seafoam to clean the top end from time to time?

That's a really great question. I've done the seafoam thing to many engines in the past....here's a tip though, best place to do it is in a school parking lot or empty huge parking lot on a Sunday because you will be putting out so much smoke from the tailpipe that people will think something is on fire....lol........

I do run a catch can on my 6.6l gas engine but I'm curious as to how much it didn't "catch". In a few weeks I'm going to install the S&B cold air intake on it. Seems like it might be good time to shove a boroscope in the intake to see what really is going on. I bought a cheap boroscope for my iphone years ago that honestly sucked. I think I need to buy one that will work with my android phone with much better viewing quality...