PCV Catch Can Question

[kschachn]

First off, sorry for yet another PCV catch can question. I know it has been discussed to death here and elsewhere, but I am having a mental block in figuring something out.

On my Toyota 1MZ-FE there are two hoses, one is on the back bank and it connects between the PCV valve (inserted into the valve cover) and the intake manifold. On the front bank there is a simple hose between the valve cover and the air intake duct (no PCV valve).

So if I install a catch can, do I need two of them? One for each hose? It looks as though most of the oil residue is coming from the front bank hose, but admittedly it is difficult to see the back bank.

Thanks.

 

[mechtech2]

One in, one out.
The one from the intake duct is the inlet. You do NOT want a catch can there.

AFTER the PCV valve, install your catch can in that line.

If you are using a common air line water separator, remove the filter, esp for winter. Then run the flow BACKWARDS from what is listed by the flow arrows on top.

If you unscrew the reservoir to dump it [the drain is too slow with thick fluid], make sure the 'O' ring seal is in place. If you lose it, use teflon tape on the threads. You don't want leaks here.

Keep the unit away from exhaust manifolding.

Now, clean your TB bore and plate with solvent, and the can will keep it that way much longer.

 

[dhise]

I had some spare time to make one of these up for my subaru using a air line separator and was surprised to see how well it works! I immediately regreted not getting a bigger one though because with the cooler temps it does get out alot of water vapor with a little bit of oil.

So if you can, try to use something that can hold a descent amount of liquid.

btw, no mileage gains to speak of, but the pcv lines after the catch can are very clean now.

 

[kschachn]

All right, I've still got the stupids.

The line from the front bank to the air inlet duct (not the manifold) is the one that is always showing oil residue. This is the one without the PCV valve. I would have thought that this is the one that I would like to trap oil in, to keep it from going into the throttle body for the engine. Are you saying that it is NOT this line that should have the trap?

 

[mechanicx]

Originally Posted By: kschachn
All right, I've still got the stupids.

The line from the front bank to the air inlet duct (not the manifold) is the one that is always showing oil residue. This is the one without the PCV valve. I would have thought that this is the one that I would like to trap oil in, to keep it from going into the throttle body for the engine. Are you saying that it is NOT this line that should have the trap?


That is your filtered air intake for your PCV system. If you want to get rid of that line you will have to plug the hole in the air intake and install a filter for it to the engine. Here's the thing, probably the reason you are getting oil in that line is because these engines have poor PCV. You are probably going to make the matter worse or no better with a catch can. If you don't have direct injection then the oil coming through that line is of no real consequence.

My thinking is these engines are so small and they are in low vaccuum/high throttle conditions so much that the PCV valve is closing or just not flowing that well, so you get pressure back through the PCV intake and the oil. This is why smaller engines usually have an air/oil separator instead of a valve. That, and they don't create as much blowby as a bigger engine. But a catch can is not going to work better IMO except near WOT if even then. That's some of the reasons why I think you should forget about the catch can.

 

[mechtech2]

Cars can get a bit of oil vapor residue in that inlet line.
Normally, they are pretty dry.
If you PCV system is not sucking through the way it should, you will often see a lot of oil in the inlet. Lots of engine blow by will also do this.

Do like mechtech said, and install it where he said.