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Old 27-11-2011, 21:05   #16
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Re: Blow-by Causing Oil Leaks

The problem with the breather to the intake is if the engine is tired and pumping a bit of oil this oil fed into the intake becomes a fuel. The added boost of more fuel and a bit of piston sealing during the compression stroke by adding oil to the cyls produces more pressure in the cyls so more bypass when the cyl fires which makes more pressure in the crank case which sprays more oil into the intake ....... A runaway diesel on a suicide mission, a common small diesel pick up truck problem.
If you use an oil catch tin and drain it regularly then it should be ok. Feeding it into the exhaust would also require a catch tin to stop the vacuum created in the crankcase from sucking all the oil out.
Either way, get an oil catch tin first, into the exhaust just makes a little more smoke if there's a bit of oil with the fumes but into the intake you are feeding all that rubbish back through the engine. possible issues are carbon behind the intake valves and building up a heavy layer of rubbish all through the intake track.
Either way will give you a reprieve for a while but it's not a long term fix.

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Old 29-11-2011, 09:26   #17
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Found a tube from the manifold to the crankcase. Manual says it is an oil pressure regulator? Anyone familiar with adjusting,rebuilding or replacing this?
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Old 29-11-2011, 18:08   #18
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Re: Blow-by Causing Oil Leaks

What do you see when you pull the dipstick and the oil fill with the motor running?
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Old 29-11-2011, 20:57   #19
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Re: Blow-by Causing Oil Leaks

For the air breather / vent in the valve cover, there are several methods that work. running a vent hose from the valve cover to the intake air filter, running the hose to a port on the intake manifold, (most new engines are done this was as no unfiltered air gets into the engine, You can also just install a small air filter on the outlet. Seen some on LBC's (little British cars once in a while). Or the dip tube with a catch pot would work too. The Dip tube was old school engine design back before oh 1965 ish

The pressure buildup inside the engine is normal and is why ALL engines have a ventilated crankcase. Odds are your rings and everything else is fine.

Unless the oil pressure is low, under 25-30 psig, I would not adjust it. Adjusting the oil pressure is done at the oil pressure bypass valve.
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Old 29-11-2011, 21:42   #20
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Re: Blow-by Causing Oil Leaks

Thanks Chic,
I'm still confused as to how this engine has run for the last seven years without a breather.
When I pulled the rocker cover I found a baffle with a filter behind it. There is a threaded hole with a plug in it. ( in the service manual it shows the plug).
I can pull the plug, afix a tube and put the tube in a can to catch any oil that gets past the baffle and gauze filter but what about the fumes?
The warnings above not to run it to the intake (runaway diesel?), scare the pants off me.
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Old 30-11-2011, 08:24   #21
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Re: Blow-by Causing Oil Leaks

Hum..while it could be possible to increase engine speed, maybe, if the rings were really worn, I don't see the runaway diesel thing being a serious problem. After all yanmar and others run the crankcase vent to the intake manifold. There are no instances of runaway dieseling caused by the crankcase vent, in boats that I'm aware of.

Runaway dieseling happens mainly in trucks on long steep mountain descents. Even there its rare. On a boat its not going to really happen. (its really hard to find a wave long enough...)

Oh engines will run fine without a breather/vent. But it will cause oil leaks or excessive oil use via the valve stems.
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Old 30-11-2011, 08:36   #22
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Re: Blow-by Causing Oil Leaks

We catamaraners have to "back down" on big waves all the time....... There's been times I've wished I had a "Jake brake".

I'm going to take your advice and run it to th intake. Can't believe 4 Perkins mechanics have't been able to tell me how it breathes.

Thanks for your help Sailor
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Old 30-11-2011, 10:06   #23
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Re: Blow-by Causing Oil Leaks

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Hum..while it could be possible to increase engine speed, maybe, if the rings were really worn, I don't see the runaway diesel thing being a serious problem. After all yanmar and others run the crankcase vent to the intake manifold. There are no instances of runaway dieseling caused by the crankcase vent, in boats that I'm aware of.

Runaway dieseling happens mainly in trucks on long steep mountain descents. Even there its rare. On a boat its not going to really happen. (its really hard to find a wave long enough...)

Oh engines will run fine without a breather/vent. But it will cause oil leaks or excessive oil use via the valve stems.
There was a story in a local mag about a guy with a new for him boat that was going into runaway. Mostly he praised the mechanic that came out on Sunday, but the end result was the mechanic drained the excessive oil that the new owner had put into the crankcase.

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Old 02-12-2011, 16:56   #24
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Re: Blow-by Causing Oil Leaks

Your post #20 seems to be the logical aproach to solving the problem. It will show you how much blowby you are dealing with and help you decide whether to route it to the intake manifold or not.
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Old 02-12-2011, 17:35   #25
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Re: Blow-by Causing Oil Leaks

Wait a minute--weren't you finding that all the oil in the crankcase was gone after running hard for a few hours? Nothing showing on the dipstick. Where was it going? Or maybe I have missed part of this story somewhere.
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Old 02-12-2011, 17:40   #26
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Re: Blow-by Causing Oil Leaks

Running it to the intake will also create a slight suction, and the eng will burn up the fumes you are worried about.
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Old 02-12-2011, 17:47   #27
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Re: Blow-by Causing Oil Leaks

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Your post #20 seems to be the logical aproach to solving the problem. It will show you how much blowby you are dealing with and help you decide whether to route it to the intake manifold or not.
+1, even a coke bottle with a hole in the side of the neck and another hose from there to the air cleaner. this will tell you just how muck blowby there is.

"Found a tube from the manifold to the crankcase. Manual says it is an oil pressure regulator? Anyone familiar with adjusting,rebuilding or replacing this?"
With that hose/pipe to the inlet manifold, if it's easy to remove take it off and see if it's blocked. There could be like a PVC valve in there and what they mean is a crankcase pressure regulator. These PCV valves simply block up with carbon rubbish after a while, petrol/thinners/carby cleaner will wash the rubbish out fairly quickly.
If this is what's wrong Id still connect up the breather from the tappet cover to the aircleaner, lets fresh air flush the nasties out of the crankcase.

As far as the big hill or wave causing run away, motoring against a strong current or wind is virtually a never ending hill.

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Old 02-12-2011, 18:02   #28
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Re: Blow-by Causing Oil Leaks

I believe those little Perkins were built by a european manufacturer and relabeled... I forget who built them, but they dont seem to have the rep the traditional perkins have... so who knows, maybe theydesigned with no vent. It's a good question though... how does an engine get crankcase pressure in there but not burn oil. Maybe it's designed to run with the pressure....? (bad idea for oil leaks!)
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Old 04-12-2011, 17:38   #29
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Re: Blow-by Causing Oil Leaks

Progress update?
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Old 06-12-2011, 04:23   #30
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I have some of the same problems with blow by in the intake but I am also registering high oil pressure. I have a lot of leaks at both crankcase seals that I will also be replacing. I have a chance to replace the high oil pressure relief valve so hopefully that is my fix. I have a Perkins 4-108 and every mechanic I talk to tells me to just live with it. They say Perkins are oilers.
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