Air Oil Separator

[RodRunner]

I had an air oil separator installed on my Tacoma that I would empty in between oil changes and would typically get between an 1/8 and a 1/4 inch of oil in a small 8 oz. plastic cup so decided to install one on my 4Runner as well.

A typical air oil separator or “catch-can” is placed between the crankcase vent and air intake manifold, where manufacturers have a hose running directly between the two as part of the PCV system. The goal is to put a container with a filter media that allows air to flow but traps any blow-by or oil mist/vapors that can get into your intake tract and gunk things up. The picture below shows the hose, on the driver side valve cover, that needs to be removed to install the catch-can.

There are many options out there but I have always used the Moroso large body unit. I like the drain valve on it and since it is larger I don’t have to worry about checking or emptying it more frequently. They have many different applications out there, including a small body that also comes in black, but no specific kit for the 4Runner so if you decide to get a Moroso get one that comes with the 3/8 inlet and outlet fittings, and a similar bracket to the one you’ll see below if you plan to mount it in the same spot I did. Jegs has a really good selection of them.

Here is what I got…

I mounted it on the driver side inner fender, which is the same spot where I had it on the Tacoma. I had to cut the bracket and drill new holes in order to bring it closer to the fender to ovoid hitting or being too close to anything else in that area.

Here is a picture of the trimmed bracket with new holes…

…and the bracket mounted.

Here is another view of the bracket from above. Also note if you decide to mount it in this spot you’ll need to find a bolt that fits, the one you see in the picture is not part of the kit.

With the bracket on, it was time to do some test fitting and decide how to run the hoses.

I originally planned to run the hose from the valve cover close to the firewall and behind the break fluid reservoir but instead decide to take a shorter path and come through in front of it instead. I also got a straight fitting from a local auto parts store to replace one of the elbows and make it a little cleaner. I decided to route the outlet hose down towards the fender and over to the intake manifold.

I put Teflon tape on and permanently mounted all the fittings while waiting for the paint to dry on the bracket. Here is what it looks like all assembled…

With the bracket painted and dry it was time to do the final mounting.

I also tie-wrapped the hoses in a few spots to keep them from moving around or resting on any engine parts.

Lastly, I ran a hose from the drain port to the wheel well to make draining easier.

I plan to put on at least a thousand miles before I drain it and see what I get.

 

[FoCo-4Runner]

Very nice work. I have a similar plan for mine. Clean install! Thanks for posting.

 

[RodRunner]

@ 1000 miles

OK, not quite 1K miles but 950 which is close enough. I've tried to take a few pictures to give you a good idea on the amount...

... and now it can go in the bottle I've been using to collect all the blow-by oil from my Mustang, now gone Tacoma and its replacement, the 4R, over the last few few years.

 

[RodRunner]

Emptied again almost 2800 miles since the last time I emptied it above.

 

[robtmc]

Interesting. I had them on three different lines including the main PCV line from the crankcase on my old 2002 WRX and never got a drop of oil. Different engines of course.

What sort of driving do you do, as that might affect the amount of blowby as oil mist that condenses.

 

[RodRunner]

What sort of driving do you do, as that might affect the amount of blowby as oil mist that condenses.

Mostly highway and around town.

 

[SigSense]

I'm a total rookie on this Air/Oil thing, but why wouldn't a manufacturer install one of these if the blow-by somehow damaged the engine?

 

[RodRunner]

I'm a total rookie on this Air/Oil thing, but why wouldn't a manufacturer install one of these if the blow-by somehow damaged the engine?

Not having this is not going to cause catastrophic engine damage. It is just going to, over time, diminish efficiency as components get gunked up. Keep in mind that with the OEM setup that oil mist, as small as it might be, is being pumped back in through the intake manifold and will eventually start to accumulate on places like intake valve seats, etc. As rings and cylinder liners wear with use they loose the ability of maintaining their seal/compression. As a result the amount of blow-by that occurs can increase and result in more of the junk you see in the pictures above getting pumped into your intake.

I would say on a vehicle you don't plan to keep for a long time this really isn't necessary because if that blow-by does eventually cause an issue it becomes somebody else's headache. If you plan to keep your truck for a long time it is just a little bit of an insurance policy for a healthier engine down the road.

 

[philsey]

....

... and now it can go in the bottle I've been using to collect all the blow-by oil from my Mustang, now gone Tacoma and its replacement, the 4R, over the last few few years.

Um, OCD much?

 

[hishaun84]

I do the same things on all of my vehicles. I was amazed at how much oil was collected from the AOS/catch can setup on my STi. That was a little more crucial because oil can lean out the A/F ratio and cause detonation in a vehicle that requires higher octane fuel. I don't think it will have a huge impact on the 4runner like the OP says, but it's a cheap insurance policy and a simple way to keep the intake system clean and efficient.

 

[RodRunner]

Um, OCD much?

Actually, while it may appear that way to you, it is simply convenience. It just collects in there until it is full and then it can be dropped off at the county's hazardous waste drop-off facility.

Let me know if you have any other constructive questions I may be able to answer for you.

 

[robtmc]

I do the same things on all of my vehicles. I was amazed at how much oil was collected from the AOS/catch can setup on my STi. That was a little more crucial because oil can lean out the A/F ratio and cause detonation in a vehicle that requires higher octane fuel. I don't think it will have a huge impact on the 4runner like the OP says, but it's a cheap insurance policy and a simple way to keep the intake system clean and efficient.

Agreed. I started doing it with my supercharged Mustang due to the oil vapor being known to promote detonation. Same with my turbocharged WRX. I doubt the 4Runner is affected by it, but I like clean innards on my engines.

 

[SigSense]

If you plan to keep your truck for a long time it is just a little bit of an insurance policy for a healthier engine down the road.

Thanks for the informative response, I love learning new ways to make my vehicles last longer.

 

[Saker]

[MENTION=107824]RodRunner[/MENTION]

I like what you did here, great idea!
We can thank the EPA for clogging up our intakes with blow by.
I remember when we use to just vent this off with a breather cap on the valve covers!....wait I'm telling my age! :lol:

Did you use the Moroso 85481 ?

Thanks

 

[RodRunner]

[MENTION=107824]RodRunner[/MENTION]

I like what you did here, great idea!
We can thank the EPA for clogging up our intakes with blow by.
I remember when we use to just vent this off with a breather cap on the valve covers!....wait I'm telling my age! :lol:

Did you use the Moroso 85481 ?

Thanks

85481 is correct. That comes with the bracket you see in the pictures. I got mine from Jegs

Oh, and you were talking about one of these...

Nope never seen those :thumb:

 

[OBW2011]

Great write up!

After reading this post I ordered and installed one of these, only thing I did different was use all the fittings that came with the set up, and I haven't put the drain hose on yet.

 

[RodRunner]

Very nice.

 

[NuclearN8]

This seems like a really great idea on a brand new vehicle.... For a used vehicle/engine however I don't know how beneficial it would be as the engine has already been exposed to this pcv blow by oil for thousands of miles...

 

[OBW2011]

well, now..!

This seems like a really great idea on a brand new vehicle.... For a used vehicle/engine however I don't know how beneficial it would be as the engine has already been exposed to this pcv blow by oil for thousands of miles...

How many miles do you no longer consider your engine viable for improvement? Thousands of miles is nothing and Toyotas have been known to last well over a hundred thousand plus miles... I have just over 50k on my Runner and have performed every scheduled service, my engine is in great shape and I expect to see those hundred of thousands plus miles with ease. Worse case my engine runs cleaner and last longer. All for a minor amount of $ and time.

 

[mdogg]

Not having this is not going to cause catastrophic engine damage. It is just going to, over time, diminish efficiency as components get gunked up. Keep in mind that with the OEM setup that oil mist, as small as it might be, is being pumped back in through the intake manifold and will eventually start to accumulate on places like intake valve seats, etc. As rings and cylinder liners wear with use they loose the ability of maintaining their seal/compression. As a result the amount of blow-by that occurs can increase and result in more of the junk you see in the pictures above getting pumped into your intake.

I would say on a vehicle you don't plan to keep for a long time this really isn't necessary because if that blow-by does eventually cause an issue it becomes somebody else's headache. If you plan to keep your truck for a long time it is just a little bit of an insurance policy for a healthier engine down the road.

Sounds good in theory, but I'm not sure it works in such a measurable way in the real world. As has been mentioned, perhaps there are valid scenarios for a catch can (such as increased boost applications where detonation becomes a concern). However, I'm not sure there is any real headache involved for this motor beyond 50k or even 100k potentially. Any concerns over longevity or durability would be displayed in the used market. However, when people are paying ridiculous amounts for this vehicle in the used market, I'm going to say the catch can isn't worth it. There's no difference between a 190k motor and a 200k motor in the marketplace (and I highly doubt you would see anywhere near a 10k mile difference with this mod).

I'd be willing to bet that Toyota has already tested (not guessed) and measured amounts of oil in various PCV designs and has probably chosen the most reliable given the cost (additional routing/hardware) and outcome (number of additional reliable miles to expect if you remove the oil vapor). I would guess that the Toyota guys already know the marginal at-best nature of removing the extra oil vapors from this particular engine/intake. If you get an extra 1k miles out of this over the course of its life, was it worth the $100+ and installation time and time spent emptying it?

How many miles do you no longer consider your engine viable for improvement? Thousands of miles is nothing and Toyotas have been known to last well over a hundred thousand plus miles... I have just over 50k on my Runner and have performed every scheduled service, my engine is in great shape and I expect to see those hundred of thousands plus miles with ease. Worse case my engine runs cleaner and last longer. All for a minor amount of $ and time.

Can you define "cleaner" and "last longer" in an objective way using numbers? You already stated that Toyota motors are known for lasting well over a hundred thousand plus miles. I wonder how many of those 100k+ motors used a catch can vs. how many of them did not use a catch can. My point is that you might be "enhancing longevity" by going from a 250k motor to a 251k motor by this mod... unless you have some data to provide.

Not to mention, how many people keep a vehicle to the outer limits of its engine life? If you don't, you won't realize any gain from this mod, and are simply wasting your money.