Catch cans for puff of blue smoke at startup?

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Hi,

In another thread, I posted about a plume of blue smoke at startup on my 06 EZ30d H6 3.0 Tribeca.

I was offered all types of opinions and oils to use etc. I don't want to turn the thread into a how to address the issue to type of thread.

What I'd like to do is understand under what circumstances a set of catch cans might reduce the plume of blue smoke on startup. Searching around the internet, quite a few people claim that adding catch cans can reduce or eliminate this smoke.

I know that it won't do a thing for consumption, but I'd like to see what if it can do anything for the smoke at startup.

Here are 3 scenarios that were identified as a root cause and I'd like to know if the catch cans might help reduce smoke for and what I believe the answer might be:

1) Bad Valve Stem Seals...no
2) Bad Rings....yes
3) Clogged PCV system....(already replaced the PCV valve and I am using Kreen in the oil to clean the system)....maybe?

Thanks for your thoughts!
 
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From personal experience, I know that adding a catch can can eliminate blue smoke on startup. When my fiancee's 07 Mustang GT was puffing blue smoke on startup when the car only had around 14,000 miles on it, I went to the internet for help. Many people on the Mustang forums suggested adding a catch can. I did this and the blue smoke on startup was gone. This engine pulls a lot of oil through into the intake from the PCV valve. The hose going into the intake used to be soaked with oil. Now it just barely has an oil film.

It is not always valve seals that cause this. On your vehicle though, I have no idea how many miles are on it and if it has high mileage, then it is possible that it could be valve seals or something else.

Wayne
 
Thanks so far! I might as well post the link to the other thread to assist. I'd like to not see the plumes of smoke regardless of consumption.

Ignorance is bliss, look at the state of our country.

Those who suggested replacing valve seals willy nilly have never worked on a boxer engine...especially a 3.0....

https://bobistheoilguy.com/forums/ubbthreads.php/ubb/showflat/Number/4219872/Searchpage/1/Main/259756/Words/dx92beater/Search/true/Re:_Best_High_Mileage_5w-30_oi#Post4219872
 
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Originally Posted By: circuitsmith
Is it possible to pull an intake manifold and look at the intake valves to see if they're oily?


I really don't have the answer to that. I am not sure whether or not that is a difficult task and the Subaru community is not that supportive to be honest. I wonder if pulling the throttle body tube might help. For the $48 I just paid for a set of baffled catch cans, it will make a decent diagnostic tool without being invasive. If they help, I'll keep them. If they don't, I'll toss them on my Forester XT.

I just put a piece of paper on the oil filler cap with it running and it didn't budge. Starting to wonder if this is valve guides as opposed to valve seals. Everyone claims that valve seals on Subarus are not likely to go bad, but no one ever gives specifics as to which motors.
 
I'm not a Subaru expert, never owned one. Since this is a boxer engine, is it possible that oil from the cylinder walls is sneaking past the rings after shut-down? If this is happening, I don't see a catch can helping that scenario.
I have had occasional smoke at start-up on horizontal cylinder engines that I attributed this to. How frequently does this Subaru smoke at start-up?
 
Originally Posted By: JetStar
I'm not a Subaru expert, never owned one. Since this is a boxer engine, is it possible that oil from the cylinder walls is sneaking past the rings after shut-down? If this is happening, I don't see a catch can helping that scenario.
I have had occasional smoke at start-up on horizontal cylinder engines that I attributed this to. How frequently does this Subaru smoke at start-up?


It has been smoking at every startup in proportion to the time it has been shut off. Overnight = huge plume of smoke. Startup after long highway drive = huge puff of smoke.

Bring to grocery store, shut off and turn back on in 30 minutes = no smoke.

Maybe you are right with it being a boxer engine.

What scenarios might a catch can help under? I am not an expert either....but there are just too many posts out there claiming that a catch can stopped smoke at startup.

I ordered a baffled set with breathers just to try out.
 
Catch cans help when the PCV system doesn't separate oil from blow by gasses very well. That reduces the amount of oil in the air intake, and reduces blue smoke as a result.

That in mind, I don't know how much they actually help.
 
Originally Posted By: artificialist
Catch cans help when the PCV system doesn't separate oil from blow by gasses very well. That reduces the amount of oil in the air intake, and reduces blue smoke as a result.

That in mind, I don't know how much they actually help.


This is my understanding as well, thanks
 
My Subaru does not smoke at startup but as always seemed to be use oil from the day I bought it new. I was told this was normal for an boxer engine because of it's design.
 
Originally Posted By: TurboFiat124
My Subaru does not smoke at startup but as always seemed to be use oil from the day I bought it new. I was told this was normal for an boxer engine because of it's design.



It is. When oil is in the cylinder bore of an inline or V engine, gravity pulls oil off the cylinder walls and back into the sump. In boxer engines, the process is much slower because the oil has to travel horizontally instead of vertically. When my dad bought his 1971 Toyota Corolla, he avoided the Subaru partially because he was warned about this.

In radial aircraft engines the problem was even worse, as the lower cylinders filled with oil due to gravity pushing oil downward.
 
I have a set of them, but haven't tried them yet. Will come back and let you all know what happens.
 
It seems to have addressed the blue smoke at startup, but on the PCV side it fills a 450ml can in about 300 miles! If I could somehow remotely route the drain I'd be a happier camper.
 
What brand of catch cans are you using? Some have drain valves at the bottom of the can. I have a Bob's Auto Sports catch can that has a ball valve on the bottom of the can that makes draining easy. You can also screw a nipple into the bottom of the valve and attach a hose to the nipple to drain under the vehicle.

Wayne
 
Originally Posted By: wtd
What brand of catch cans are you using? Some have drain valves at the bottom of the can. I have a Bob's Auto Sports catch can that has a ball valve on the bottom of the can that makes draining easy. You can also screw a nipple into the bottom of the valve and attach a hose to the nipple to drain under the vehicle.

Wayne


I am using Ebay VMS style catch cans. I found out that they are 500ml. Would/could the nipple at the bottom be left open with a hose or would that cause a vacuum leak?
 
Originally Posted By: dx92beater
Originally Posted By: wtd
What brand of catch cans are you using? Some have drain valves at the bottom of the can. I have a Bob's Auto Sports catch can that has a ball valve on the bottom of the can that makes draining easy. You can also screw a nipple into the bottom of the valve and attach a hose to the nipple to drain under the vehicle.

Wayne


I am using Ebay VMS style catch cans. I found out that they are 500ml. Would/could the nipple at the bottom be left open with a hose or would that cause a vacuum leak?

The can that I'm talking about has a drain that is meant to stay closed until you need to drain it. All you have to do is move the lever 90 degrees and it drains. This company doesn't provide the nipple I'm talking about but they are not hard to find. Here is the ball valve on the can I'm talking about.


Here is the inside of the ball valve on another can that shows the threads where you attach a nipple to. This catch can actually came with the nipple but I didn't use it due to space limitations of where I had the can mounted.
 
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