Universal 25 Air Filter

Ed Balun

Member I
I have a 1987 E32-3. The engine has a circular air intake on the top of the engine. I opened the top of this anticipating to see an air filter of some kind. There was none. I asked around the dock and other owners said an actual filter wasn't really necesary. Is an air filter needed for these engines or what?
 

jreddington

Member III
I ran into the same situation with my Universal M15/5411. Circular filter at the end of an short length of rubber hose. No filter inside and I haven't been able to locate a filter that fits it. I also note that either OEM or PO configured it close to the crankcase vent tube. That way, most vapors get sucked into the inlet and combusted.

Positive
- Minimizes any smell or mess from crankcase vaoprs in the engine compartment.

Negatives
- If you overfill the crankcase and get too much vapor engine will run on and not shut down. Combine this with the weird way the dipstick tube, crankcase and dipstick interact to make reading crankcase level difficult, this can happen. From personal experience I can tell you about the heart in your throat feeling when you find your engine running away and not being able to shut it down.
- If you put a filter in the inlet, vapors will probably help it attract dirt and clog up.

Since in the marine environment, dust and grit, are much lower than auto applications, it's probably OK to go without a filter and its restriction on air flow. I note that while my lawnmower has a filter (absolutely necessary in this application), my snowblower does not. Again, a snowblower sucks in a lot less dust and grit than a lawnmower.

I've had my boat about 10 years now with no filter. Would be interested in other folks experiences and recommendations.
 

Geoff Johnson

Fellow Ericson Owner
Mine has only a foam filter around the outside of the metal cage. Of course, that does not stop my yard from trying to charge me for a new filter every year!
 

rwthomas1

Sustaining Partner
FWIW, the Universal 5432 factory intake "horn" was not a filter, just a screen with maybe 1/8" holes over a 1"x1.5" opening. IMHO, the intake opening was too small and restrictive yet offering no filtering. I replaced it with a much larger K&N universal filter. Certainly there is now much less restriction and better filtering whether needed or not. Why not? It was cheap enough. RT
 

Keith Parcells

Sustaining Member
air fiter

You can get a porous foam filter that wraps around the outside of the cage from Torresen Marine - Marine Diesel Direct. It gives me some piece of mind to have it there. My alternator just gave up the ghost & it was giving off bits of metal from its' case as the bearings died. I would hate for those to be sucked into the intake, though it is on the opposite side of the block.

Keith
E33
:egrin:
 

Maine Sail

Member III
I did this

I found a K&N filter at a motorcycle shop with the same diameter as the intake throat on the M-25. Sorry I can't remember the part number. The arrow is pointing the the 90 degree brass fitting I inserted for the PCV valve I made.


Here's a picture of the PCV set up I made. The hose runs from the valve cover to a brass nipple with barbed fittings. Inside the brass nipple I rolled up some oil absorbing pad, loosely so as not to restrict flow, to absorb any stray oil escaping the valve cover so it would not pass to the intake. I would change this at each oil change. By adding this PCV valve I no longer had any oil smell in my engine compartment after running the engine. The factory set up just vents the crank case into the engine compartment! If you add a K&N make sure you have enough room in the underside of the filter for the 90 degree fitting for a PCV. My K&N was off set slightly giving me room to drill through the bottom and insert a fitting. I purchased all the brass fittings at Home Depot and did the whole project for under $50.00.
 
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newgringo

Member III
Another Crankcase Vent plan

I too have a circular foam filter in the factory air inlet horn of my Universal 5411 (21HP). Gives me piece of mind about keeping who know what out of my engine. Now as for crankcase venting I plumbed from the valve cover fitting to the top of the air inlet with 1/2 inch ID hose. It intentionally is routed in a big semicircle arc to enter the air inlet just outside the foam filter element. The theory for the hose arc is that any oil drops exiting the valve cover run back to the engine. The picture shows this setup with things disconnected for another project. You get the idea. Had it that way now for about 1 1/2 years. Works perfect.
 

Attachments

jreddington

Member III
When I bought my boat my vent routing just ran to the front of the inlet horn, secured with a circular key ring type clip pierced through the end of the rubber hose and through a small hole drilled in the horn, not a tight fit. This seems to work since I don't get any unusual oil or diesel smells in the cabin. The general airflow into the horn draws any vapors that way.

This has always looked like a kludge arrangement and I always wondered what the "official factory routing" should be. It would seem this should vent outside the hull somehow but never found a reference about it and seems like from this thread, "official" means just venting into the engine compartment.

I'd be a little leery of routing the vent line to anywhere downstream of a filter. Any filter, even clean provides some restriction and therefore at least a slight vacuum on the inlet manifold. When a bit dirty or clogged, this vacuum can become significant. With the hose solidly attached between the filter fitting and the crankcase this could translate into significant vacuum in the crankcase and pulling too much oil vapor. Might contribute to excessive oil use and worst case, provides a direct route for the oil to the combustion chamber which can result in an uncontrolled engine runaway.

I've experienced this event personally when I accidentally had too much oil in the crankcase. It is quite a puckering moment when you realize you can't shut your engine down.
 

rwthomas1

Sustaining Partner
This has always looked like a kludge arrangement and I always wondered what the "official factory routing" should be. It would seem this should vent outside the hull somehow but never found a reference about it and seems like from this thread, "official" means just venting into the engine compartment.

I'd be a little leery of routing the vent line to anywhere downstream of a filter. Any filter, even clean provides some restriction and therefore at least a slight vacuum on the inlet manifold. When a bit dirty or clogged, this vacuum can become significant. With the hose solidly attached between the filter fitting and the crankcase this could translate into significant vacuum in the crankcase and pulling too much oil vapor. Might contribute to excessive oil use and worst case, provides a direct route for the oil to the combustion chamber which can result in an uncontrolled engine runaway.

I've experienced this event personally when I accidentally had too much oil in the crankcase. It is quite a puckering moment when you realize you can't shut your engine down.
I know a bit about diesel engines in road going vehicles. Simply venting the crankcase gases to the atmosphere is known as a draft tube. Thats how they did it in the old days before anyone knew or cared about emissions issues. Simply venting outside the air intake inlet will allow the gases to be pulled in and burned which is an improvement. Crankcase venting directly to the intake manifold, that is, post air filter/air inlet is extremely common. I own 3 vehicles that are setup this way from the manufacturer. Yes it is possible to have a "runaway" condition if the engine is extremely worn and there is lots of blowby with this setup. Old VW diesels are known for this when they get to 300K and up. Yes you are correct that placing the crankcase vent tube inside the intake system will subject it to a slight vacuum. Reality is unless the filter is extremely restricted, worn out or you put too much oil in it there will be no problems whatsoever. An engine actually runs better with a slight vacuum in the crankcase. The vacuum scavenges the blowby gases, helps the piston rings seal and even lessens the chance of oil leaks past seals.

Incidentally, there are a few ways to shut down a runaway diesel. On small diesels you can get away, sometimes, with placing a board over the air intake to kill it. Do not do this on a large engine or try with a rag. The vacuum developed is EXTREMELY powerful and it will suck in anything other than a very solid object. The other way is to cut the fuel line. Unfortunately it will take a while for the fuel in the injection system to be used up. Cracking the injector lines, or simply cutting them with a bolt cutter will shut down the engine immediately. Granted all of this, except plugging the intake, only works for engines with defective injection pumps ie. runaway caused by a mechanical problems. The quickest and most reliable way to shutdown a runaway from blowby gas or anything else is a CO2 fire extinguisher shot into the intake. CO2 means no oxygen for combustion and the engine stops immediately usually without damage. RT
 
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jreddington

Member III
Yes, the runaway I'm referring to is with excessive blow by. Cutting the fuel lines or killing the injectors won't stop the engine in this case since the fuel is not diesel, but the lube oil vapors or mist being pulled into the engine. I don't have any direct experience in this but I understand that failed bearings on diesel turbochargers can also be a source of engine oil into the intake and resultant runaway. (Not planning on turbocharging my 11 hp Universal M-15 any time soon :rolleyes:).

In my instance, I realized that the source of the "fuel" was the open end of the vent tube. Simply pulling it away from the intake area promptly shut down the engine. At that time I was still learning the idiosyncrasies of measuring oil level in my Universal M-15,. Thought I was losing oil and added waaaay too much oil to the crankcase.

As you said, a shot of CO2 will shut it down. Probably any other type extinguishers will do the same but do damage (including hydrolock) to the engine internals. Also hitting the decompression lever works but can also cause internal engine damage.

Solid blocking on the intake will shut it down with no damage as long as the blocking isn't broken and sucked into the engine. In fact, while working at a Liquefied Natural Gas in Indonesia, my truck, along with all vehicles that entered certain areas, had to be diesel to avoid high voltage sparks setting off any gas leaks. However, in the event of a leak, the gases mixed with air also can provide fuel for runaway. All vehicles were modified with a solenoid operated valve in the inlet. That way even in the event of a of runaway (which I never experienced there) you turned off the "ignition" which killed power to the solenoid, and the intake valve snapped shut. It made a distinctive "snap/clang" every time you turned off the engine.

RW, on your diesel engines is there some variation of a PCV valve in the line to help control pressures and flows? While a similar piping arrangement, the PCV valves and lines on automotive gasoline engines, tapping in downstream of the throttle plate, do work differently than a pressure/flow control valve would in the marine diesels we're talking about. I have to poke around the Torrensen diesel engine forums to see if there's additional information there.
 

newgringo

Member III
Another Crankcase Vent Plan - clarification

To clarify, my vent hose enters the air horn UPSTREAM ie outside of the foam element. It is the same scheme I have seen on other marine engines I have worked on. Anything that lets the engine eat up the blowby gases is nicer than blowing them into the engine compartment - yuk.
That's is an interesting comment about engine running more efficiently with a vacuum in the crankcase. If I am not mistaken the NASCAR engines evacuate the crankcase big time to reduce what is called "pumping losses". But doing so requires really good main bearing seals and other gasgets. Not something I think any of us sailor types want to mess with.
I like that motorcycle filter. Neat. Not sure the PVC valve is needed, but won't hurt either.
Happy Venting -
 

rwthomas1

Sustaining Partner
I am very acquainted with a few diesels. The old VW IDI 1.6liter diesels just have a hose from the valve cover to the intake manifold. There is an oil separator in the valve cover thats just coarse wire wool in a metal baffle, no valve to speak of. Basically the same setup on the late model VW TDI's like my wifes '03. My 84 Mercedes 300D has the same setup as VW but runs the crankcase gases through an outboard oil separator, the oil is returned to the sump and the gases dump in right before the turbo inlet. 93 Chevy 6.5 TD work truck has a thing called a CDR valve on the valve cover. Its really a large one-way valve to keep the engine from taking in air at that point. The outlet of the CDR is simply dumped in right before the turbo inlet. Hope this helps, RT
 
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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Maine Sail, may I ask a stupid question?
Since all of the different crankcase vent solutions seem to bring the vapors back to the air cleaner... What does your "PCV valve" do?
Great photos, by the way!
Thanks,
Loren
 

Maine Sail

Member III
Loren,

It takes any fumes directly back into the intake MINUS any oil that makes it into the hose because the rolled up oil absorbing pad, inside the brass nipple, catches any "oil mist" or "stray oil" that makes it out of the valve cover and into the PCV hose.

From the factory many of those vent hoses, that are placed close to the air intake, drip oil from time to time and if you inject the vent directly to the air filter oil could possibly make into the intake if not stopped first by the oil absorbing pad. While oil into the intake is not going to hurt the engine it could certainly make it smoke a little more. Don't roll this pad to tightly though as you don't want to restrict air flow.

Hope this info helps..
 
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