Catch cans (8 Viewers)

[sunrk]

Just saw a promotional post from Allfourx4 (a local 4wd parts and service place based here in Newcastle Australia) pushing oil catch cans using the tagline of '100000 km without a catch can' and a picture of some sort of assembly that's gunked up in a Terrain Tamer clutch kit crate.

From my layperson way of thinking, they seem like 'snake oil' products like Hi-Clone air intake 'swirlers', etc.

Why would one be used? Why would one be needed? Note those are two very different questions.

My 80's never had one and the motor (n/a 1hz) is pushing up close to 700 k km's.

Happy to hear views about catch-cans. Are they something that is specific to diesel engine vehicles or do people fit them to petrol/gasoline engine vehicles too?

 

[AirheadNut]

Catch cans filter oil mist out of the blow-by gasses from the valve cover. This prevents oil from building up in the intake and burning in the engine. The photos of carbon buildups you are seeing are likely from engines with EGR; the problems arise from the oil mist mixing with the soot in exhaust gasses in the intake manifold. Here is an example from a VW TDI manifold that I helped my brother clean out:

Basically, if your engine has EGR a catch can is a really good idea. If not, it isn't super important but still helps clean up exhaust smoke from burning oil and keeps the intake from getting oily.

 

[mudgudgeon]

If not done right, they do next to nothing.
Or, they can restrict PCV flow, and pressurize the crank case and cause oil consumption, and oil leaks

 

[duncanrm]

A catch can on a naturally aspirated diesel engine without a turbo and without EGR just adds unnecessary engine bay clutter.. and the only reason to add a catch can to a turboed diesel engine (without EGR) is to prevent oil build up in an intercooler if one is fitted.

 

[MUDZLLA]

What if you ran the crankcase breather under the engine so it coated the frame with oil mist and helped prevent corrosion? Hmmmm....

 

[MUDZLLA]

Does the PCV system draw combustion products into the crankcase and contaminate the oil? I mean what is the point of having a negative pressure inside your engine?

 

[AirheadNut]

Does the PCV system draw combustion products into the crankcase and contaminate the oil? I mean what is the point of having a negative pressure inside your engine?

It is actually venting blow by gasses that leak past the piston rings out of the crankcase, if the PCV system were to be plugged the crankcase would pressurize and blow out the dipstick or possibly some oil seals. I’ve had this happen a couple of times: once it blew out the dipstick and drenched the engine bay in about a quart of oil, the other time it pushed oil past the turbo seals and into the exhaust.

 

[Irish11]

What if you ran the crankcase breather under the engine so it coated the frame with oil mist and helped prevent corrosion? Hmmmm....

Ah, you mean how my 3b sends a nice oily mist all over my transfer case and underside to keep it safe from the rust demon. Its so thoughtful that way.

 

[sunrk]

Is the real reason for considering a catch can actually that a really worn diesel engine can self-feed and be difficult to shut off? I personally haven't met anyone who's had an experience with that. My 1hz has the crankcase vented straight back to the intake. Being non-turbo there's no one-way valve. I've not noticed what effect, if any, that might cause complications compared to not feeding the crankcase exhaust back. But then again I've never had the engine apart with the head removed from the block.

 

[AirheadNut]

I suppose that is possible, but IMO highly unlikely. In my case, the first Prado I had didn't have a lot of blow by, but enough oil mist came out the crankcase vent that there was a light haze coming out the exhaust at idle. Once I installed a catch can, the haze went away. On my TDI Prado I have a catch can that vents to atmosphere. A little oil comes out the vent, but the catch can prevents the CCV from making a mess of my undercarriage with oil spatters.

 

[sunrk]

So could it be said that catch-cans are a bit of a 'greenie effect' maybe? What bothers me is that catch cans seem a bit like DPF's in that they are trying to solve a problem the cheap and easy way that may not really be a problem. What do you do with the catch can filter (is it actually a filter?) - is it a throw-away bin item going to landfill? Do you capture/store/re-use the liquid contents? Standard oil filters are a throw-away item for most people doing their own DIY service and maintenance.

Is the catch can something derived by manufacturers and industry due to the rise of high-pressure common-rail diesels where fuel system and engine tolerances are much tighter?

 

[mudgudgeon]

They are nothing more than cool accessory for a lot of cars. Good for 5 horse power!

They also have legit usefulness.
They can and do collect oil vapour from the crankcase vent if they are made and installed well.
They are something you should empty accumulated oil out of with every oil change. It's used oil, and as old as the rest of the oil in the sump, so it's waste oil.

They prevent intercoolers on turbo cars from clogging up, and keep intake piping and manifolds clean and gunk free.

The trick is, they need to slow the oil vapour filled air enough that oil is no longer airborne, it collects within chambers in the catch can. But if they are too restrictive, slow the air flow to much, then you get pressure in the crank case

 

[chapel gate]

from the point of view of the engine. its best to vent to atmosphere. i cant be bothered to get involved in any other side of the debate.
back in the day, all diesels vented to atmosphere.

whilst still getting a very high mileage out of a toyota 1H whatever, the PCV set up coats the back of the intake valves with carbon. add in the EGR, the entire intake system gets gunked up.

 

[sunrk]

whilst still getting a very high mileage out of a toyota 1H whatever, the PCV set up coats the back of the intake valves with carbon. add in the EGR, the entire intake system gets gunked up.

Is there a way to sort this out? I've never had the head off the 1hz in my 80 since I bought it 12 yrs ago, and it's quite possibly performing sub-optimally as a result (plus all the other usual things like injectors needing renewal).

I have not actually seen a landcruiser of any model with a catch can but people who might be doing heaps of outback touring in modern common rail diesel 4wd's probably look at fitting them.

 

[aztoyman]

When working properly, they are similar to the oil separators you see in compressed air systems. Like mentioned, older diesel crankcases vented to atmosphere. They vent To prevent pressure building and causing leaky seals and such.

Newer engines have emission regulations so the crankcase gasses and EGR get dumped back into the intake. Solves (hides) one problem but causes others. Like gunked up intake systems and contaminated oil.

People that run catch cans are trying to capture the oil before it goes back into the intake. Some people just want to catch as much oil as possible before venting it to atmosphere. Some people say they can smell the fumes when venting under the hood so they run it back further or into the exhaust pipe. Lots of thread out there. Even for gas engines.

 

[duece71]

Being new to all of this, if there were a catch can installed, where would it be located?

 

[duncanrm]

Being new to all of this, if there were a catch can installed, where would it be located?

Somewhere in the engine bay.. can you post a few photos of your engine bay, we'd soon identify it.

 

[duece71]

Somewhere in the engine bay.. can you post a few photos of your engine bay, we'd soon identify it.

Ok, will do. I am out of town for work and will post pictures next week when I get back.

 

[Dusten]

So could it be said that catch-cans are a bit of a 'greenie effect' maybe? What bothers me is that catch cans seem a bit like DPF's in that they are trying to solve a problem the cheap and easy way that may not really be a problem. What do you do with the catch can filter (is it actually a filter?) - is it a throw-away bin item going to landfill? Do you capture/store/re-use the liquid contents? Standard oil filters are a throw-away item for most people doing their own DIY service and maintenance.

Is the catch can something derived by manufacturers and industry due to the rise of high-pressure common-rail diesels where fuel system and engine tolerances are much tighter?

Catch cans are used on more than diesels.
They aren't snake oil and aren't a gimmick.

On a diesel system that doesn't actually experience vacuum in the intake tract they're less useful.


But you see them all the time on power gas motors. My lightning has one.

 

[duece71]

Here are the pictures of the engine bay…..
Any ideas where the “catch can” might be located. New to all of this, thank you for your replies.