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Crankcase vent OIL IN BREATHER

Posted by Anonymous on


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  • Harley Davidson Master
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Hi Anonymous, year and model please. Thanks

Posted on May 15, 2015


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Posted on Jan 02, 2017

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SOURCE: crankcase pressure causing oil to come through

needs piston rings at least!

Posted on Aug 01, 2009

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SOURCE: oil coming out crankcase breather new hi output

is the oil coming out while riding? doubble check to make sure oil lines are hooke up proprely. may also be putting out too much pressure for system. Sholud be a spring and or check ball may be week or stuck

Posted on Sep 01, 2009

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SOURCE: crankcase breather

If the bike sits for a while, and then you run it and shut it off, it will drip.. run it more often.

Posted on Apr 28, 2010

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SOURCE: 89 Harley FLTCU oil coming from the crankcase breather tube and

This is an age old problem for the Harley engine. In you 89 model, the crankcase breaths from behind the oil pump through a tube that runs to the backside of the air filter assembly. Most people that I know, simply remove the tube coming up to the air filter and block the hole in the air filter assembly backing plate. At the breather, they run a short hose to just behind the transmission and cut it off there. This is similar to the earlier Shovelhead engine and the way it breathes. In 1994, Harley went to the "head breather system" which was better but it still gets oil into the air filter assembly.

There is one thing I saw on the aftermarket assessories market once called a "CatchCan". The breather tube ran to it and it seperated the oil from the air and the held it in a small container to be emptied on a regular basis. I have never used one nor have I ever seen one so all I can tell you is what the book said. Matter of fact, I cannot remember where I saw it now. Custom Chorme catalog, maybe. Good Luck, Steve

Posted on Apr 30, 2010

  • 6 Answers

SOURCE: my 95 xr600r dirt bike leaks oil

This hose should be connected to the air filter box.

It's for ventilation of the crankcase, much like the PCV (Positive Crankcase Ventilation) in cars. As the bike runs, the crankcase gets hot enough to vaporize some of the oil. And since there's always at least a little bit of combustion blowby in the cylinders, you get a bit of fuel/air thrown into the mix and an oil/fuel/air "atmosphere" in the crankcase, which isn't an ideal situation. So, when the hose is connected to the air filter box, it slightly vacuums off this atmosphere, letting the engine burn it and expel it through the exhaust.

If it's not connected to the airbox, the vapors can condense back to oil and just drip out.

If a lot of oil is coming out ("a lot" is hard to quantify), you could be getting excessive blowby because of a broken ring or cracked piston.

Hook that breather line back up to the airbox and unless the bike smokes excessively, I wouldn't worry about it.

If it IS hooked up, it or the airbox is cracked and needs fixing/replacing. If the breather line has somehow become plugged (mud-daubers are amazing at finding holes to makes homes out of), the pressure buildup could have split your vent line.

Posted on Jun 01, 2010

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What causes excessive crankcase vaccum, besides pcv. Pcv confirmed OK and functioning, all vacuum lines routed correctly 07 f150 5.4 3 valve

I can only think there is a fault somewhere in the pcv system that has somehow been overlooked.

The vacuum part of the pvc system provides the motive power for the flow of clean fresh air through the crankcase and into the inlet manifold via two routes, taking with it the various crankcase emissions to be burned up during the combustion process.

At idle and low revs and other times when manifold depression is high, such as during overrun, crankcase emissions tend to be drawn through the pcv valve directly into the manifold and at other times, when engine speed and load increases the venting increasingly takes place through a second vent into the air cleaner or intake. At low speed, etc. the second vent becomes the supply of clean fresh air for the crankcase.

In the early days of the pcv system some engines had fresh air supplied via a filter fitted to the crankcase and others used a vented oil filler cap. A few engines had no air inlet at all and the manifold was simply connected directly through a length of half-inch hose to the valve cover. Those engines almost never leaked oil...
For a few years BMC used a complicated vacuum regulator valve mounted on the crankcase and again a large bore hose to the manifold.

Since those days most manufacturers have settled on one of two systems using either a pcv valve or a small air bleed into the manifold to provide the motive power for the ventilation of the crankcase. Mostly there is a flame or spark arrestor/oil mist trap in the breather that sometimes becomes blocked and causes trouble, though the trouble is usually the opposite of too much vacuum.

I suggest you go back to the drawing board and recheck everything. During a service I usually test the breather by putting the compressed air blow-gun down the dipstick tube and sealing it with a cloth. If the crankcase breather is clear and working properly no pressure will build up inside the engine.
Obviously some caution is needed to avoid blowing out seals and gaskets if the breather is found to be inadequate.

Aug 08, 2015 | Cars & Trucks

1 Answer

Gl1100 crankcase breather tube leaks oil

Hi, Anonymous and the usual suspects are:
1. Oil tank/system overfilled.
2. Faulty breather valve.
3. Engine breather hose bent, pinched, kinked etc.
4. Air filter has too much "pre-oil".
5. Crankshaft seal failure allowing transmission fluid to migrate.
6. Blow by drain tube cracked/split or filled to capacity.
For more information about your question and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day.
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83 GL1100I oil coming out of Crankcase vent GL1100 Information Questions...
Honda GoldWing GL1100 Service Manual
Honda Gold Wing GL1100 Owner Manual

Jun 18, 2014 | 1983 Honda GL 1100 Innerstate Gold Wing

1 Answer

77 shovelhead w joe hunt mag and s&s oil pump everything is great except after about 20 mins of riding oil start coming out of gasket all around cam cover and mag assembly dont know what would cause...

There ae a number of things it could be. What it sounds like to me is that the oil is not being pumped back into the oil tank and is collecting in the cam chest. It should be blowing out of your crankcase breather tube as well if your crankcase breather tube is open. Behind the oil pump, there are three holes. One is behind and above the oil pump. This is where the breather tube from your oil tank and the primary comes into the engine. The hole directly behind the oil pump in the middle is the oil return line from the very back end of the primary where the oil from the primary is recirculated back into the engine. The bottom hole behind the oil pump is the crankcase breather. It should have a hose that runs back around behind the transmission and just dead ends in a bracket pointed towards the final drive chain. This hose should be open to vent the crankcase pressure. Have you checked to see if oil is being pumped back into the oil tank? If not, the scavenge gears of the oil pump may not be pumping the oil out of the engine and back to the tank. If this is the problem, you may not have the drive key properly installed in the scavenge gears of the oil pump. Still, oil should be pouring out of the crankcase breather hole. But, this is what it sounds like it's doing to me. The oil is building up in the cam chest for some reason.

Good Luck

Sep 06, 2011 | Harley Davidson FXDWGI Dyna Wide Glide...

1 Answer

93 Fatboy oil leaking from vent tube at air filter. oil level is good, not over filled, oil will cover the oil tank on a 100 mile trip

On your '93 model, the crankcase vent is down low on the engine behind the oil pump and it runs up to the air filter through a metal and rubber hose. I don't know how many miles you have on your engine but it you're getting any blow-by on the rings, this will increase the pressure in the crankcase. Most people simply re-route the crankcase breather underneath the bike and plug the hole on the backside of the air filter. Replace the metal line with a rubber hose and put a small filter in the end of the hose. Route the hose back behind the transmission and attach it to the transmission mounting plate just in front of the rear wheel.

This was the way the older Shovelheads were done from the factory for years until the EPA made them start running the crankcase vented air through the engine. In 1994, Harley went to the "head breather" system and moved the crankcase vents to the heads. Still, the oil mist in the vented air builds up in the air cleaner on these models as well.

Good Luck

Apr 12, 2011 | 1993 Harley Davidson FLSTF Fat boy

1 Answer

Oil system manual for a 1987 softail (evolution). oil leaking from breather of engine system.

On your '87 Softail, the engine breather vent is behind and below the oil pump. The air from the breather is routed into the engine air filter by a metal pipe and rubber tubing that runs from the breather vent to the air filter. It is common to get a bit of oil in the air filter because of this system. The system was designed to meet EPA regulations of the time. Since then, the breather system has been modified to allow the engine to breathe at the top of the heads instead of down low on the engine. This resolves some of the problem with oil getting into the air filter but it still does not eliminate it. The only way to eliminate the oil from getting into the air filter is to reroute the air from the crankcase breather vent to somewhere else. Most people just let it exhaust underneath the bike by putting a small breather filter on the end of a short piece of rubber hose connected to the breather vent.

Good Luck

Apr 01, 2011 | Harley Davidson FXST Softail Standard...

1 Answer

Oil from air filter

Due to EPA regulations, since 1985 Harley-Davidson had to move their crankcase breather tube to the air cleaner. The crankcase vented air had to be "recycled" through the engine. As a result, a fine mist of oil in the vented crankcase air condenses in the air cleaner and must be cleaned out from time to time. A lot of riders are purchasing "relocation" kits to change the location of the vented air. These kits are available from Kuryakyn and Custom Chrome.

Good Luck

Mar 02, 2011 | 2000 Harley Davidson FLHRCI Road King...

1 Answer

Oil blows out filler, checked breather hose in air cleaner housing, ok.

If your machine is filled with more than 21 ounces of oil the oil will be forced out the crankcase vent and leak out the filter. Check your oil level, correct if needed. If the oil is good you may have a bad crankcase vent.
look for help from a local dealer like

Feb 13, 2011 | Craftsman 675 Torque 190cc 21" RearBag...

1 Answer

I have a 1200C Sportster and an after market breather I still get the oil coming out of the breater holes, I have replaced the top end gaskets and still get the oil on my right side of my bike can you help...

Blame the EPA for this. The EPA requires that vented crankcase pressure be routed through the intake system so that it can be burned in the engine. So, Harley used the "head breather" system to route the crankcase exhaust into the breather resulting in oil building up in the air cleaner assembly.

As you noticed, I'm sure, that the large bolts that hold the air filter backing plate on are hollow. This is where the crankcase pressure is vented. There are several aftermarket kits that are available to reroute this pressure so it won't mess up your air filter.

Good Luck

Oct 23, 2010 | 2001 Harley Davidson XL 1200 C Sportster...

2 Answers

Oil blowing out throttle body on filter and blowing down the side of bike. I had a new crankcase breather valve kit installed one month ago. It was fine until two days ago. All o-rings were replaced also.

The oil may not be coming out of the throttle body. The crankcase breather system is actually in the rocker box covers. Yes, there is a breather gear in the crankcase but that is for the oil return to the oil pump.

The crankcase ventilation system vents crankcase pressure into the air cleaner as required by the EPA. The purpose is to route oil mist contained in the crankcase ari that is vented into the engine to be burned. There are 'umbrella valves" in the center section of the rocker boxes. Over time, the heat makes these pieces get hard and brittle since they are made of a type of rubber. When this happens, they don't stop the oil mist as well as they used to. The oil mist is blown into the air filter where it coaleses into drops of oil. This is normal for any Harley due to their engine design.

But, if it's too bad, I'd suggest replacing the umbrella valves. Simply remove the top and center section of the rocker boxes by removing the six bolts that hold the parts on the top of each cylinder. Replace the umbrella and the edge gaskets and replace the covers. Torque the bolts to 10-13 foot pounds.

Good Luck

Jun 21, 2010 | 2000 Harley Davidson FLHTCUI Electra Glide...

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