After using a very high-density coalescing filter for more than 6000 miles, I continue to be impressed as to how much oil it traps. However, due to the LS1's inherently low vacuum pressure and mild flow conditions, there's always a small amount of oil aerosols that escape and can be seen lining the return tubing. Although the amount I've seen is not worrisome, I decided to do what many in the compressor industry do - combine a particulate filter to trap bulk liquids and particulates with the same incredibly efficient 0.3 micron coalescing filter.

Now, because seasonal weather allows for wide temperature swings, condensed water in the air heading toward the intake is a given. Here's what the particulate filter had in it after 1000 miles or so:


That's some oil with quite a bit of water. "Wow", you might say, "That particulate filter does a good job at trapping liquids; why not use just it?"

.....not a good idea, since the Watts coalescing filter that was plumbed downstream has at least an ounce of water and more oil in it. This is a warning that anyone who thinks a Home Depot particulate filter is a good catch can is sadly mistaken. It is good at catching liquids, but allows aerosols to fly on by.
The good news is that not a spec of oil got past my double whammy filter combo. The bottom line, at least at this time, is that filtration efficiency depends upon not only the type of filter, but also the sequence used when different filters are combined.

In order of efficiency (IMO): Least to best:

Simple catch can, no filter media
CH particulate filter
High-end catch can, SST mesh or scouring pad media
Low-flow particulate filter
Low-flow coalescing filter
Combination of the last two (in that order)

In other news, someone asked me how hot the PCV line air gets - good question since some filters have clearly labeled operating temperature limits. To find out, I attached a temperature probe to my HOBO data logger:



I located the data logger itself near the filters (see pic), but the probe is T'd in at one of the warmest areas - near the PCV valve. More driving time is needed, but after a 15 minute drive and up to 214F oil temps (6-minute idling), the PCV line air reached 160F. The area around the filters (as shown in pic) never exceeded about 65 degrees F, mostly because my cold air mod brings outside air in from below. In fact, even when the oil temp hit 214, the entire area around the Halltech filter was very cool to the touch. outside temp was about 65F.

Anyway, more testing time is needed and I will drive the car for a few days more to see if the PCV line temps get any higher.

Oh, and Howie, the Watts particulate filter (F504) filter element threaded holder does not need a gasket. Its tapered nose seats tightly against the countersink in the aluminum top piece.

Dave

 

Yes, lots of water condensation in the crankcase during colder times of the year. Cars ran in very cold areas may actually collect that brown crap under the filler cap which runs slightly cooler because it's up on a plastic neck on the valve cover. Seen this happen on other vehicles too.

I always like a good thermal test with temp probes in use. I take it the temp probe went down into the brass fitting that was right after the PCV valve. I don't doubt that the dirty crankcase vapors get pretty hot, and I'd say the vapors coming out the PCV line are probably pretty close to oil temperature when everything gets thermally stable.

I see in your photo that you don't run anything in the fresh air line ... how much oil film do you get in that line?

 

Dave,

Several months ago, I read your article about the coelescing filters, printed it out, and have it stored in my 'things to do' folder. However, I still haven't got around to installing any type of catch can. It's never received much priority, primarily because this problem is "out of sight, out of mind".

Last week, I posted that I removed my intake manifold to fix the P1416 air pump check valve behind the engine. While I had my intake off, I looked inside my throttle body and there was alot of tar and gunk all around the perimeter of the blade. Also, when I turned my intake manifold upside down, black liquid oil ran out of one of the runners - not a few drops, mind you, but it was a solid stream running until I noticed it and quickly turned it back upright. Now my focus has once again turned to the need for installing some hardware to stop this.

You obviously have done more investigative work on this problem than anyone I've ever seen (I bet as much as GM themselves).

Could you please post the brand names and model numbers of the coelescing filter(s) you recommend, in which order they should be plumbed, and a recommendation for location in a stock C5 engine bay. If that's a problem with CF rules, could you please PM that info to me. I intend to jump on it this time.

Thanks in advance.

 

The probe is sealed within the T hose, similar to how you would plumb in a vacuum gauge.
Zee, I think you may be correct, although my next test may be to check the hose's air temp at the filter where the ambient temp is much cooler.
Here is what I've got after 32,000 miles:


....not much, I would say.

Dave

 

Thanks, Bell. I try to learn something new as often as I can! Regarding the filters I am currently using:

The first one in-line with the PCV-to-intake hose is the
Watts 504-02DH (a particulate filter that is a bit more "open" when compared to the F501 coalescing filter). This is followed by the Watts F501-02DHX67 (coalescing filter that includes a mounting bracket).

I swapped the zinc body of the F504 with my extended length aluminum housing, since much of the non-aerosol liquids will be trapped there. Keep in mind that if I had room for only one filter, it would be the F501 coalescing assembly. This is what I ran for 6000 miles and from what I can see in the return hose, only a small amount of oil made its way through. But this is why I'm trying out the combo - so far (1000 miles), so good - no oil in the hose.

I am going to start testing a new design (when I get back to work, where there are a few environmental chambers) soon, It will include a Watts F501, but will have a newly designed top piece and body. More info will follow. I can PM you with more info as the testing progresses.

Dave

 

Dave,

If you've got 6,000 miles with very little carryover with just the particulate filter and 1,000 miles with practiacally no oil carryover in the downstream hose with the particulate and coelescing combo, what's the reason for experimenting with a new design? Just curious.

Also, I seem to remember from long ago, at one time you had some extended bodies made and were selling them to CF members, but after those were gone, you haven't offered to make more. Do you think there would be problems with using the original (i.e. not extended) body?

 

Well, I'm trying to eliminate all carryover oil. Fortunately, I've seen very little large-particle contamination (and really, there shouldn't be if the oil filter is doing its job), but as you know, every engine is different in the amount of blowby chemicals that pass through the PCV line. Some LS1s are so tight that even after 1000 miles, no oil is trapped. Others literally dump oil into the catch can. Therefore, starting with a coalescing filter is probably the best way to go. If its can fills up quickly, then a "prefilter" to catch most of the liquid stuff is most likely a good addition (upstream, of course).
The only reason why I am not ordering more extended cans is essentially because I am ready to test the new design. Should it survive all tests, it will replace the current version. I can certainly get ahold of more Watts filters (within a couple of weeks) if you need something soon. Those filter bodies hold only one ounce each, so you would have to keep an eye on the level.

 

Thanks Dave for the research and reports. I have your other articles on my Favorites and used your information when deciding to install my oil/water extractor filter and coalescing filter on my C5s ( I choose Binks because they offered an 8oz anodized retention tube , full indicator, 1/2 NTP connections and I got a deal at $40 new, LOL ). I don't have any particular problem with oil but no oil contamination to throttle body, intake , valves ect is the goal.

Appreciate your intention on a practical education.

 

Thanks for the kind words, Dave! I'm glad I can be of help.

 

Yes, I'd say you don't have any real backflow down the fresh air line. Others get huge amounts of oil down the fresh air line, but they are usually the ones who run WOT at the track a lot. Do you track you car at all, or just street drive? Could also be that you motor is very tight and has minimal ring blow-by.

 

Once or twice per year, I participate in a "Mountain Cruise", which has no resemblence to most "cruises"! It is during one of those that I may see the oil temp reach 260 degrees F from plenty of high-rpm, high-load driving. Normally, though, I keep the revs below 4500 rpm. Regarding the rings, I would say that blowby is average for a C5. I add a quart every 2500-3000 miles.