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How does the crankcase breather work and what does it do?

How does the breather work and what does it do ? How does it effect the starting process

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When an engine is running there are compression gases escaping past the ring gaps into the sump. the crankcase breather allows this build up of pressure in the crankcase to escape before it gets high enough to blow out the oil seals. In modern cars the gases are drawn out by a PCV valve that is connected to the inlet manifold and this valve is opened when the vacuum exceeds the spring tension of the valve.. If there is a faulty PCV valve ( clogged from oil gunk build up,carbon or the like ) it may affect the starting of the engine by upsetting the fuel/air mixture. In modern EFI controlled engines this will probably result in the ECM being unable to correctly set the air/fuel ratio for starting as the mixture may be too lean . If this valve is faulty --run the fault codes and a code will appear or simply change the PCV valve and make sure that the hosing is fixed tightly.

Posted on Nov 21, 2014

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Posted on Jan 02, 2017

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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

What should the air intake breather look like on a 1996 chevy blazer


Hi there:


An air breather replaces the intake vent hose on your crankcase, which vents the spent gases inside your head out into the atmosphere instead of back into your intake track. This keeps your engine clean and in top condition. Aside from that, air breathers also improve the appearance of your engine bay.


Installation of an air breather is a simple process that takes minutes. Simply remove the hose on your crankcase and replace it with this breather. Most breathers come with a clamp already included.


For parts replacement visit this Air Breather brands: Chevrolet/1998_9999_Blazer Intakes Air Breathers
In the follow video, checkl 5:20 minute about location...


Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Jun 21, 2012 | 1996 Chevrolet Blazer

1 Answer

Oil cap and dipstick covered in creamy sludge, is this breather prob as not losing any water


Yes, it could be that a plugged up Positive Crankcase Ventilation (PCV) valve or engine crankcase breather (with filter) is the cause allowing moisture to condense in the crankcase. However, if the valve and breather are okay, a cylinder compression test should be done to verify that the cylinder head gasket is not leaking. Regardless, the engine oil should be drained and the engine flushed with clean oil and an appropriate crankcase flush additive. Entrained water in the oil (the creamy sludge) will damage engine bearings quickly.

Mar 05, 2011 | Volkswagen Golf Cars & Trucks

1 Answer

Oil is getting on air breather 2004 ram hemi


Hi,
oil getting on a breather can indicate excessive crankcase pressure. Check all the `crankcase breathers and the valve cover breathers.

if the crankcase has been overfilled with engine oil. The crankshaft has to "beat" it's way through the oil and thus acts as a pump and sends oil all over the internal surfaces of the crankcase.

If the engine cylinders have developed 'blow-by" they will also contribute to an increase in crankcase pressure which will be evident by oil in the breathers. The fumes / pressure in the crankcase are designed to be removed by the engine breather system, and drawn through the engine etc.

I hope this info helps.

Jan 25, 2011 | 2004 Dodge Ram 1500

1 Answer

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.

Apr 26, 2010 | 2000 Harley Davidson FLSTC Heritage...

1 Answer

Oil in air breather


sounds like you have too much oil in the engine (should normally be around 500-600ml when there is too much oil, it gets past the piston rings and pushes it through to the head.

May 20, 2009 | Briggs & Stratton Briggs Stratton Vanguard...

3 Answers

TRACTOR BLEW WHITE SMOKE, AND STARTS TO SPUTTER


Start with making sure your oil lever is not over full. If it is it may be getting into the crankcase breather hose that goes to the carburetor hence the white smoke. Sometimes also you can blow a gasket in the breather system and it will do the same. Check for oil leaks in the breather system. Hope this helps. donnyb60

Mar 02, 2009 | Craftsman 20 hp 42 in. Deck Lawn Tractor -...

1 Answer

Oil sump mod or fix


Deep sumps are to keep the pickup in the oil at all times even when the front end is way off the ground - I don't think it'll have any effect on sending oil out the crankcase breather. An aftermarket tail-mounted breather box will keep oil out of the airbox but it's expensive probably hard to find nowadays, and forces you to reroute a lot of wiring as well as relocate your computer box. Simpler to just do fewer and smaller wheelies,,,

Nov 10, 2008 | 2001 Ducati 996 S

1 Answer

Oil sump mod or fix


Deep sumps are to keep the pickup in the oil at all times even when the front end is way off the ground - I don't think it'll have any effect on sending oil out the crankcase breather. An aftermarket tail-mounted breather box will keep oil out of the airbox but it's expensive probably hard to find nowadays, and forces you to reroute a lot of wiring as well as relocate your computer box. Simpler to just do fewer and smaller wheelies,,,

Nov 10, 2008 | 2001 Ducati 996

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