Catch Can

Due to normal wearing of cars' engines after several tens of thousands miles hot gases from cylinder start to escape by the ring of the pistons inside the engine or on the other side of the pistons. Since the engine is closed by seals and gaskets, pressure starts to build up. Depending on how much the engine is worn, more ore less gas have to be released in order to obtain maximum efficiency. Also. Exhaust gases may have water and gasoline in them. Water would emulsify the oil and gasoline would thin it.

However those are exhaust gases and unburned fuel, you can't simply let them escape in the air. Most manufacturers choose an option design called PCV (Positive Crankcase Ventilation). It's a very simple idea. When pressure builds up (certain rpms and engine output) a valve opens (PCV valve) and lets those gases back into the intake manifold. The parameters of the process are more complicated, cause manifold vacuum that varies with the rpm and output. A simple valve is not the best solution but this is what we got on most cars.

PCV valve is usually placed on the valve cover in the highest point to avoid oil that splashes to escape into the circuit and into the intake with the gases. However that is an ideal that never happens.

Every time when i replaced a PCV valve i saw it had oil in it. And sometimes oil cooks in there and stuck the ball and spring of the valve either open or closed, again decreasing engine efficiency. But i never had a major problem with it until i owned a Hyundai.

Hyundais are different from other cars at least by two accounts. Valve cover is minimalistically low. Main design engineer there who worked at Daimler chose to copy an improvement from Daimler which they also took from diesel engines. The so called swirl flaps. There are two rows of butterfly like valves inside the manifold that open and close according to vacuum (first row) and actuated by computer (second). Those are installed in there to create turbulence and again get you a few percent of more gas mileage.

Now comes the interesting part.

I recently installed a modified filter for water to catch the oil from PCV line. The filter was transparent and i could see inside it's not only oil coming on PCV line. Oil is emulsified by the water present in exhaust. When that emulsion ends in the intake somehow interferes with the functioning of the first row of flaps, those actuated by vacuum. It changes the weight of the flaps on one end and they start oscillating, creating variations in engine's functioning which in the end translate in vibration. Vibration that surpasses the design performance of the exhaust manifold sealing gasket and starting intermittent exhaust leaks. Again vibration transmits to the hood that intermittently opens and let small amounts of exhaust pass by the seal and into the cabin fan intake. Shall i say more?

The filter i installed after a few improvements catches most of that emulsion however it restricts the flow of gasses at certain rpms decreasing efficiency.

The problem is known to car enthusiasts from race cars. There are what they call oil catch cans that costs up to hundreds of dollars. I once found a cheap one on Amazon made of blue anodized aluminum, looking nice and shiny, and... one quart capacity (hard to find a place under the hoos).

The lead's sealing gasket was made of cardboard and looked weak and i didn't want to take the chance for parts of that gasket to get into the intake so i sent it back. Drop of efficiency with installed filter is more severe in town and generally when accelerating when pressure builds up inside engine. I finally decided to build my own catch can. First i went to NAPA to buy some connectors. Had no idea what to attach them to. The idea was to go later to Home Depot or Lowes an buy anything that looked close to a can and had a detachable lead (you need a detachable lead because you have to screw the connectors). However, conveniently next to the connector there was what they call a "brake bleeder".

Don't know, in auto mechanics slang, for some reason they call purging of the brake fluid "bleeding". At Les Schwab they even have the so called "power bleeder" LOL. It's some sort of round reservoir with several gallons of brake fluid in it where at one end you attach a hose with compressed air and the other all sorts of adapters that go in the place of master cylinder reservoir. Pressurized brake fluid would go into the reservoir. On cars at each wheels brake caliper and pistons have a small screws with halls call again... "bleeder". You unscrew those a bit and usually can have someone press on the pedal to "bleed" the system then screw them back when the pedal goes up. With the power bleeder though, one person can do it. But it's very wasteful. The caps would not fit really well on top of master cylinders and much fluid is lost on the floor. However. You could purge the whole brake fluid from lines and reservoir and cylinder and replace it with new one.

The brake bleeder from NAPA works in the opposite way. You are supposed to attach a vacuum hose (supposed you have a vacuum pump) at one end and connect it to the bleeders at the wheels. Or just attach it and use it to just collect the fluid. While pumping on the pedal fluid would not go on the floor but in the can and air would go out on the other connector. Why it was there at NAPA next to the air connectors? Did they know i was looking for something just like it?

Anyways. It has a tight sealed lead, two connectors and it seemed to fit the purpose. However when i came home and cut those connectors which where too small and again would obstruct the PCV flow, i realized it was all made of cheaper plastic, not nylon as i thought. There is a serious chance it would melt at summer. While working at it was thinking of gluing those connectors that i almost self thread in the very tight holes i made in place of built in connectors, an idea came to me. Why not making the whole thing out of a... tin can. Drill the holes, force self thread the connectors, use JB weld to seal them and voila. Only trouble would be i would not be able to see inside and empty the can. Don't know yet.