Hi, I see there are two nipples on the oil filler neck, the top one has been capped off, but the bottom one facing downwards is left open and I can see signs of oil dropping, I believe the previous owner has taken off all the emission stuff,
does this bottom nipple need to be blocked off also ?

 

you tricked me with the thread name
why would you do that.......

 

run the top one to the upper intake manifold (<---WRONG. do not do this.) and run a silicon line vented up from the bottom nipple to stop the leak. the permanent fix is to get a catch can.

 

right, if I wanted to set up a catch can, just run a tube from the top nipple to the catch can,
block the bottom one off ?

where does the other tube on the catch can need to go to ?

thanks

 

DO NOT BLOCK OFF THE BOTTOM NIPPLE!!!!! this will result in oil going into the housing and cause mass smoking upon driving. along with oil all in your intercooler pipes and intercooler, run the top nipple to the upper intake manifold (<---WRONG. do not do this.) and for the time being if you want to drive the car put a silicon hose on the bottom nipple, and make sure its vented up zip tie it to something and enjoy.

 

oh sweet thanks for that,

What would I need to do if I run a catch tank ?



regards,

 

Wait what? Really? My car is single turbo and the previous builder has the same thing. Blocked off the bottom nipple and the a vacuum hose running up to the UIM.

 

im on a single set up also if i block my lower nipple i get oil in the housings and crazy smoke. lol also tired on another single FD and it did the same thing......

 

The purpose of the two nipples on the oil filler neck are to pull a vacuum in the crankcase. Do NOT attach it to the manifold without a PCV or check valve to keep your crankcase from getting positive pressure from boost. On stock sequential setup, the bottom nipple should be attached to a nipple on the intake pipe of the primary turbo. This doesn't require a check valve as it's on the intake side of the turbo which does not get boost.

Most folks eliminate the line that goes to the manifold (by capping the nipples) because the PCV valves fail over time, either sticking open which results in boost leak and positive pressure in the crankcase or closed which would be the same as eliminating the line.

Pulling vacuum in the crankcase means that you're pulling the blow-by gases through the (primary) turbo, IC, piping, throttle body, and manifold. I can attest that there was oil residue on the inside of all this when I had these parts off the car to the vacuum hose job on my car. As a result, some folks recommend installing an oil catch can on the line that connects the oil filler neck to the nipple on the intake pipe of the primary turbo.

http://www.rx7.org/Robinette/pcv.htm

 

Thank you f2racer! The below is 100% correct.

Nothing personal guys, but if *you're* not 100% sure that what you're posting is 100% correct, don't post it.

Running a hose from the UIM to the oil filler neck is about the worst thing you can do. You're trying to DE-pressurize your oilpan, not run boost into it

Also, the two nipples go to the same place, down to the oil pan. bottom vs side doesnt matter.

My 2 cents, I've had different catchcan setups over the years, and finally settled on a very simple one---- on my oil filler neck, one of the nipples is blocked off. The other nipple has a 6mm vacuum hose that runs to a Greddy catchcan. The second nipple on the catchcan has a breather filter over it.

Previous to this the second catch can nipple had a hose running to a corner of the engine bay as a vent, and it wasn't working very well (at all). I was getting oil in my charge piping and my BOV was making a mess in my engine bay. Since making the simple change of the breather filter the problem has completely went away.

 

Rich

So just to clarify, right now the previous owner has one of the nipples blocked off (the one pointing down) the other I believe he had running somewhere but I will have to take a look at pictures to figure out where he was running it, but where should I run the side one if I don't have a catch can?

 

When installing a catch can, I run lines from both nipples and vent the can with a filter. I have found that on some cars one line is not enough to prevent pressure from building. Two lines solves the issue, so I just always run both.

Here is a customers car with twins and limited space:

 

I'm assuming you drilled a tapped for a barb fitting for the breather on the Greddy catchcan?

Damn, limited space is right....... that engine bay has like zero room

 

Seriously. Looking at that I didn't realize just how much stuff I've relocated.

 

I've considered going with a breather tank, similar to what you describe that simply vents to the atmosphere through the breather's filter:

http://www.summitracing.com/parts/SUM-G1504/

But at the end of the day, I figured a crankcase under vacuum was best. Since my car still has the stock seq twin setup, I wound up with a poor mans' catch can built out of an oil compressor filter that sits in between one of the (in my case lower) oil filler neck nipple to the nipple on the intake pipe of the primary turbo, which is how the stock setup is without the catch can in the middle. This setup seems to work well.

http://www.pbase.com/rsrock/oil_catch_can

Unfortunately many of the vacuum hose diagrams don't show where these connecting so I've circled them in RED on the attached diagram. I also wound up capping the nipple on the UIM that connects to fuel vapor purge control system which I circled in GREEN. I run those lines to another catch can. BTW, that can has never seen a drop of anything in that can, so I'm guessing that the lines were clogged to begin with or that I have a faulty solenoid. Capping it also meant that I was eliminating another point of boost leak from the overall equation.

BTW, Steeda makes something that looks remarkably similar to a oil compressor filter and sells it for about 6-7x the cost.

http://www.steeda.com/products/steeda_oil_separator.php

 

Kind of confusing.

For someone with a single turbo setup: top nipple will be blocked off, where goes the other one? I don't have an oil catch can.

 

Stock the top oil fill neck nipple goes to a plastic PCV valve that goes to the upper intake manifold. Mazda got rid of this in '95.

The bottom oil fill neck nipple goes to the primary turbo inlet duct.

If you are single turbo I would get a catch can and route both nipples to the vented catch can, similar to what Banzai Racing is talking about up above.

I love these catch cans -


Run 2 lines from the 2 oil fill nipples to the 2 nipples on the catch can. I usually make a little bracket to hang it off the left stud on the brake booster that the brake master attaches to, mount it low kind of under the TB elbow. Been running this on my car for 10+ years and have done it on a number of other FD's with no problems.

Now, if you are hitting the track and doing a lot of track time that's a whole 'nuther thing, there's a lot of threads of track guys trying to keep catch cans from filling up. A healthy motor with street use should have no problems with that Jaz setup. I typically empty the catch can when I do an oil change and it's not even close to full.

If you leave the nipples vented it will make an oil mess everywhere. If you cap them the oil pan will pressurize and you'll get smoke in the exhaust big time.

Dale

 

Dale, that's a perfect can and has a drain valve..! Thanks... Are you running this? Any pics of it installed? Just to have an idea of the size.

 

Yep, I've run one for years. About the size of a Coke can or so.

You can easily make a bracket to put it where I mentioned, on the brake booster stud.

The nipples will fit a 6mm size hose very nicely and snugly. You can also put a drain hose on the drain valve that sticks out under the car so you could empty it quickly if you needed to.

Again, I've never had my car on a track so I don't know how this would do in a track situation.

Dale

 

I had a catch can about that size and it'd fill up after every session. I've since gone to a larger 1 qt can along with an IRP baffled fill neck. Since i've changed out the neck, i've hardly gotten any blow-by and the 1 qt can is now overkill. I believe Jaz makes a larger can with an option for opaque material so you can see how full it is. If you don't track it, the smaller can is probably fine

 

There's nothing on the market that could be bolt-on, without drilling some holes/building a bracket? And what's the purpose of both threaded fittings?

Thanks for your help Dale.

 

I don't think there's a good bolt-on solution out there. The good thing is the bracket is SO simple and basic - 3 holes and a 90 degree bend. I found a metal bracket at the hardware store that was a roof tie or something that was almost perfect. Drilled a few holes and done.

The 2 fittings go to the 2 nipples on the oil fill neck. Run 2 hoses and you're all set. The catch can that I linked should just have regular hose barbs to hook up to, I think they have another version that has threaded fittings for AN lines which is total overkill.

I'll see if I can get some pictures up of my setup this weekend so you guys have an idea of what I'm talking about.

A bolt-in setup would be nice but the bracket is so simple that I doubt anyone would make it. It's one of those things that if someone made it as a product no one would pay the cost since it's so basic of a setup.

Dale

 

Ok thanks Dale I'll try to build it myself but I was born with 2 left hands.

 

I took Dales advice and am using the Jaz catch can. At some point both vents on the fill neck got blocked off on my recent rebuild. I had noticed excessive smoke while it was idle. Glad I found this thread and thanks Dale for for stud location on the booster works great. Here is how I did the bracket and location that Dale mentioned.

 

This thread is kind of confusing. If talking about USDM cars then the advice given is correct. But any post-December '95 car only has the pre-turbo vac line hooked up and the other nipple of the filler neck is capped off from factory. Probably wont help the OP now as the post was from 8 years ago , but may help others fault finding JDM cars .