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Old 07-10-2010, 07:18   #1
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Risking Runaway ?

Here is the skinny: I have a Pisces marinized Isuzu 2ba1 2 cylinder 27hp diesel with around 2400 hours that does not have the crank case breather routed to the intake horn (factory set up, not modified). There is a small amount of blow-by causing a bit of smoke in the cabin when running. My plan to correct this (re-ringing is not an option right now and there is no power loss or other issue with how the engine runs) is to install a new blower and vents utilizing 4" hose instead of 3", and to fabricate a metal hose and attachment points connecting the breather to the intake horn. My questions are: 1. Should the mushroom breather be replaced with a sealed connection linking the breather tube to the intake, or should I fabricate a tray under the mushroom for the tube to the intake, allowing it breathe at atmospheric pressure? Is there something about the design of this particular engine being the reason for this not being done at the factory? 2. Am I setting myself up for a potential runaway caused by the oil vapor from the crank case the engine will now be breathing? Thanx for any knowledge/advice shared!
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Old 07-10-2010, 07:45   #2
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Dont know this engine specifically, perhaps a crankcase filter might be sufficient, else vent to outside, Most engines never had breather connected to the air intake. better yet fix the blow by ( as this could get worse, your rings may be failing, or scoring the clyinders, do a compression test) make sure also your using a mineral oil lube oil, not synthetic.

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Old 07-10-2010, 09:12   #3
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Thanx for the reply Dave, but to my knowledge, pretty much all of the newer engines have a PCV connected to the intake or air cleaner. Most older engines do as well, but I'll admit that my knowledge base for older engines lies mostly with gasoline, not industrial/marine diesel. The issue is not bad enough to warrant a re-ring at this time, and I could probably live with it as is, however if If I can mitigate or stop it without a tear down, why not do so? As for the oil, currently using Rotella T1 30W, but may switch to 40w at next change.
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Old 07-10-2010, 09:22   #4
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Closed crankcase vent systems aren't uncommon, but are often an aftermarket thing- look up the Racor CCV for example. I suppose it would be possible to cobble together a slightly less effective, but still workable, home-brew solution using similar principles.

I wouldn't be too worried about runaway... if your crank vent is moving enough oil droplets to fuel the engine, you've already encountered bigger concerns (such as being 4000 hours overdue for a ring job, and having to top up the oil every two miles). In any case, the crank vent filter should remove most of the oil before the gases are sent to the intake.
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