Oil Catch Can, Eliminate that knock!

Been reading up a bit. Some years back, for a soap making project (which never got started ) we got a 2-pound container of Potassium Hydroxide (KOH, aka caustic pot ash), a little different than Sodium Hydroxide (NaOH, aka caustic pot ash, or lye), but with similar efficacy.



worth noting: ONLY use this on the stainless steel cooler.

Of the two, the Pottasium Hydroxide is maybe easier to get (popular in soapmaking), and more effective: Asking Google's AI:

Which would be better for cleaning carbon build-up in an automotive, stainless steel Exhaust Gas Recirculation component

The response:

For cleaning carbon build-up in a stainless steel Exhaust Gas Recirculation (EGR) component, Potassium Hydroxide (KOH) is generally the better choice between the two hydroxides.

Why Potassium Hydroxide (KOH) is Preferred

• Superior Penetration: KOH molecules are slightly smaller than NaOH molecules, which allows them to penetrate hard, baked-on carbon and grease more effectively.
• Better Rinsing: KOH is more soluble in water, especially hot water, making it easier to rinse away without leaving the hazy residue often left by sodium hydroxide.
• Lower Corrosivity for Efficiency: While both are corrosive, KOH is often cited as providing better efficiency with less risk of localized corrosion on certain metal surfaces when used correctly.

Critical Precautions for EGR Components
While KOH is effective on stainless steel, you must verify the exact materials in your EGR assembly:

• Avoid Aluminum: Many EGR housings are made of aluminum. Both NaOH and KOH will vigorously corrode aluminum, creating small pits and holes that actually cause carbon to stick faster in the future.
• Protect Electronics: Do not submerge the component if it has integrated electrical motors or vacuum diaphragms, as the caustic solution will destroy them.
• Manual Pre-cleaning: For heavy build-up, use a screwdriver or scraper to remove large chunks of carbon first so the chemical can reach the base layer.

 

Gentlemen, great discussion! I am all for an OCC installation on the Gen 3 Prius’s. However, as I understand it, California does not allow them. And their installation is an automatic fail during a smog test. I live in SoCal and I hate the notion that I would have to temporarily uninstall it every 2 years for testing only to reinstall it! Personally, I always run my cars a 1/2 quart low. So far, my Gen 3 has 150k on the odometer and, knock on wood, no engine dancing has materialized!

 

Catch cans can blow seals if neglected which is why newer factory designs were integrated into the engine and have a drain back to the oil sump.

 

It's not THAT hard to remove and install, every 2 years, is it???
WHY would you run half a quart low? They less oil, the less cooling.

And depending on whether you have the updated pistons and rings, you'll start burning
oil before too long. You should keep an eye on the oil level...

 

?? Half a quart below the full mark (i.e., 1.1 quart above the low mark), or half a quart below the low mark, which would be risky?

 

Set it up so it’s at least easy to pull out, and clean if necessary. An extra (intact) PCV hose is $10 USD at most.

 

Oil catch cans are allowed in California. However finding a smog check station that knows this is pretty much impossible. Easier for them to just say no modifications allowed and then fail you. Attached is the official California Smog Check Manual that lists aftermarket modifications that are allowed. That section is Appendix C. Page 40 lists oil separator (oil catch can) as allowed.
Sorry can't attach file since I'm a newbie. Google California Smog Check Manual and you'll find it. I'll attach link once Priuschat allows me to.

 

My Moroso 84574 (air/oil separator) came with a slip of paper saying it was not street legal, something like that. Google concurs:

Google AI

 

My guess is AI gets its information from some sort of internet search. Which predominately everyone says not legal. I would think that the official California Smog Check Manual would have correct information. In that manual on page 40 the "Oil Separator/Filter - Crankcase Filter" is listed as an approved aftermarket modification.

 

Back in the day a lot of Japanese cars had the PCV valve located on top of the valve cover, usually not too far from the oil filler cap. Our 1998 4 cyl Accord is like that, and it is stupid easy to replace the PCV valve. Moving the PCV on a Prius up there, which some think would reduce oil through the PCV valve, would require modifying either the valve cover or the oil filler cap. Modifying the valve cover would be a ton of work, but it turns out oil filler caps with a port to attach a PCV valve are already a thing, but are sold for race cars, not street usage:

https://www.holley.com/products/plumbing_an_fittings_and_hose/application_specific_parts/ls_plumbing_parts/oil_system/parts/3434120ERL

While oil catch cans in California are in the "not exactly legal and not exactly illegal" category, I would guess that actually moving the PCV valve to another location in the engine would fail a smog inspection, even if it was plumbed to an OEM PCV valve and the stock OEM hose from there to the intake.

(Apologies if this was discussed before in this thread - 119 pages and search isn't working...)

 

Really, not many SMOG check stations even pop the hood anymore. They plug in the OBD2 and make sure no check engine lights are on, and MAYBE check the CAT to see if it's OEM and that's it. Even if the hood is popped, they rarely "inspect". I'm sure it still is, however roll of the dice if you get one of those stickler guys who sees everything and is having a bad day.

 

California Smog Check Manual: Appendix C, Page 40: Oil Separator/Filter – Crankcase gas filter (oil catch can) is allowed.

https://www.bar.ca.gov/pdf/smog-check-manual.pdf

The problem is: My guess is that 99% of the guys actually doing the smog checks have never read the manual. And will just say no modifications allowed, rather than spend the time to read 40 pages.

 

Moving the positive crankcase ventilation valve to a location other than the crankcase, say the valve cover, seems quite fundamental, more likely to raise eyebrows, maybe negates its purpose?

 

Many newer Toyotas have a built in catch can that drains to the sump to prevent blown seals when an aftermarket unit is not emptied regularly. The location is not as important and is on the valve cover in many pcv designs.

As a side note, on a gen3 Prius a vacuum leak caused by a loose pcv hose or an aftermarket catch can will cause an engine no start.

 

Gen 3 has also has plain hose (no check valve) between valve cover and engine air intake. Between air filter and throttle body IIRC.

 

The whole "needs EO or Doesn't need EO" with the check marks is still vague and open for interpretation or discretion of the SMOG facility likely. So..it's best to "find a guy" who will let it go.