JKlad

Just a few quick questions.

Am looking to install an oil catch can on the PCV line south of the PCV valve and was wondering if anyone here has already done this on their JK's 3.8L? If so, would like to see any pics you have of where you mounted it & how you plumbed it in. Also, did you use one with 9mm or 15mm fittings & does your one have an internal filter screen?

Thanks in advance!

Incognito

LINK Maybe not exactly what you were looking for, but maybe it'll help.

JKlad

Thanks, that was very helpful! I was trying to figure out where I would cut the OEM PCV tube & splice in the hoses running to the catch can; your method of replacing the entire OEM tube (and keeping it intact for possible future use) with hose seems the simplest solution.

It was interesting to note in your thread that there was a considerable amount of oil (given the low mileage driven after instal) trapped in the smaller clear-plastic catch can however when you changed it over to the larger one the amount was negligible. Do you think this was related to the different sizes or designs, or simply an indication of reduced oil vapours in the crankcase as your new motor broke in?

Incognito

It's quite probable that my homemade catch-can design was at fault, hence it collected no oil. I don't believe it had anything to do with engine break-in, just faulty design. But you're right, it was interesting to see just how quickly the first clear chamber captured that amount of oil, and yes, I think you could definitely improve upon it and make way more effective at extracting the oil from the crankcase gases. You need either a larger chamber, or more chambers to condense the hot gas as it cools, or use some sort of filtering media which the air passes through.

My ultimate concern however was of the concequences of restricting this airflow too much, which would ultimately be worse on the engine than what I was trying to remedy. Thus I abandoned this altogether. Another idea also occured to me that perhaps this oil infused vapor acts as sort of an upper cylinder lubricant, though that's probably way far fetched. In any case, I've never had any problems with any vehicle I've ever owned due to it inhaling hot oily crankcase gases. In most cases, a clogged PCV valve will cause the issues.

One other option would be to disconnect both crankcase ventilation hoses leading to & from the intake altogether, and simply put a filter in on the passenger side of the engine, and run an exhaust hose down somewhere low in the engine compartment from the PCV with a catch-can attached somewhere in between that line. I've seen this done on racing applications but it's illegal in some places for altering an emission device.

JKlad

Yeah, I've been looking at different types commercially available & they tend to fall roughly into two categories: a) Simple ones that consist simply of an empty aluminum cylinder with inlet & outlet ports and a drain screw or valve at the bottom, and sell for around 20-50 bucks on ebay, and b) High quality name-brand ones that can be fully disassembled for cleaning/maintainance constructed from stainless steel, aluminum or carbon fibre cylinders with either internal baffles, a filter screen between the inlet & outlet lines, or both (some also have steel wool at the bottom as well), and sell from $150 to around $250.

The fittings for these also seem to be in two main sizes (9mm & 15mm) and I'm assuming the larger diameter would cause less restriction in a larger capacity motor such as the 3.8L. Thanks again for your input; I'll post a write-up of the install & update results of it's effectiveness when I decide on the route I'm going down.

Incognito

Well, shoot me a notification when you do, for depending on your results, I might just take up interest for this again. Good luck

Kaisoboy

Just out of curiosity why would you install one on a NA vehicle? I had one exactly like the one above on a SC car. Do the JKs suck oil into the intake on NA applications?

Cheers

f2fast4u

Read the posts from others about the oil sucking 3.8L and you'll know why, otherwise, your question is correct. On blown cars you have to be careful to not pressurize the crankcase - been there, done that.

Kaisoboy

Ok, had no idea! I'll look into it.

Thanks

JKlad

Yeah, the 3.8L's fitted to the JK Wrangler are notorious for high oil consumption (Chrysler even says a quart per 1000 miles in "normal"). Though some of this was due to batches of bad motors back in '07 (compression and oil expander rings installed incorrectly, badly honed/machined cylinders being out-of-round, etc) most of it is due to excess amounts of oil making it's way into the combustion chambers via the PCV system, causing the carbon build-up and pinging (detonation) issues that are common for these motors.

There is conjecture as to the reasons for this excess oil entering the intake via the PCV system, with faulty/blocked PVC valves being one cause while the switch in oil specification by Chrysler to the ultra-thin 5W20 for mileage reasons is another (the mini-van motor was originally designed to run on 10W30 and no noticable differences in motor design or tolerances were made by Chrysler to account for the change to this much thinner oil; they simply changed the spec to 5W30 after a few years in the minivan & then 5W20 when they put the motor in the Wrangler & that was that).

All I know is that my motor developed a pinging issue and increased consumption just on 40K miles and when I checked out the PCV system I found the valve was full of oil & gunk and the intake had a lot of oil in it (as much as you would expect to find in an old clunker with worn rings and 250K miles on the clock).

I am currently running 5W30 but intend to switch to 10 or 15W40 in a short while when my warranty expires (I live in a hot climate so don't need an oil with a winter visocity weight as low as 5 anyway). I expect that this will make a major difference (many people here on this forum have found a big diffrence in oil consumption just switching from 5W20 to 5W30) however I would like to also install a catch can to further reduce the amount of oil vapour making it's way into the intake manifold and depositing itself on my throttle body, valves, plugs and pistons. I intend to fit the catch-can while I'm still running the 5W30 so I can compare the amount of oil captured in it when I switch to the thicker stuff later.

Do a little research here on the "40K mile spun bearing club", the phenomenom affecting JK 3.8L's where suddenly without warning and usually around 40K miles, oil consumption increases exponnentially and owners (caught completely unaware as the motor previously didn't consume much oil at all) find their sump runs dry, the oil pump loses pressure, and they spin a bearing and sometimes throw a rod as well requiring a complete engine rebuild.