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[andyc]

I can see where the OP is coming from and to be honest i don't have a clue, suck it and see you never know you might have stumbled on something.

Just talking in general but when people say they have cleaned out the breathers what do they mean by cleaned out, is it just a case of poking something down the holes in the breather block?

The reason i ask is the breather may still be blocked and if you look inside one you'll see what i mean. A while back, sorry can't find the photos now, i removed the cover from the breather block.

If your a bit handy with the spanners then it is an easy job to do. First drill through the centre spot weld and then prize the cover off, its a bit of a job but it will come off. Once the lid is off you'll see all the years worth off crap thats inside

Once you have cleaned it all out you'll need the flatten off the spot weld stub left in the casing, drill and tap to six mm. Refit the cover using the grey sealant as used on the oil cover.

With the cover countersink the hole and use a countersunk screw as used on from brake discs. You'll need to use a countersunk screw as the cover is tight against the back of the head once refitted.

By doing this you can remove the cover from the breather box each time you want to clean it and saves pushing all that crud back down into the crank case.

Ran this setup on my car for a number of years and never had a problem with leakage

Like i said at the start give it a ago, get a couple of spare covers just in case and see what happens, your car your rules but let us all know how you get on

Cheers
Andy

[omega3000]

By doing this you can remove the cover from the breather box each time you want to clean it and saves pushing all that crud back down into the crank case

Makes sense to be able to access and clean the crud out  I would normally take all the adjoining pipes off to clean too rather than poke the crap down 

[dublin.jd]

If I'm honest, I thought there would be positive pressure in cam cover due to combustion gases getting by the piston rings (albeit in small amounts) and that the pressure builds up only when the breathers become blocked. I don't see how there could ever be negative pressure in cam covers as the intake manifold/plenum vacuum is in no way connected to the cam covers.
Maybe I'm wrong but I thought the only way pressure gets to the cam covers is through the oil passages that lube the cams and hydraulic lifters etc.
Someone can hopefully she'd light on this.
Thanks

[dublin.jd]

Thanks ANDYC for the positive/constructive post.
Thats good advice, I'll hang on to that.

[dublin.jd]

If I'm honest, I thought there would be positive pressure in cam cover due to combustion gases getting by the piston rings (albeit in small amounts) and that the pressure builds up only when the breathers become blocked. I don't see how there could ever be negative pressure in cam covers as the intake manifold/plenum vacuum is in no way connected to the cam covers.
Maybe I'm wrong but I thought the only way pressure gets to the cam covers is through the oil pressure, ie. Through the passages that lube the cams and hydraulic lifters etc.
Someone can hopefully she'd light on this.
Thanks

[Webby the Bear]

If I'm honest, I thought there would be positive pressure in cam cover due to combustion gases getting by the piston rings (albeit in small amounts) and that the pressure builds up only when the breathers become blocked. I don't see how there could ever be negative pressure in cam covers as the intake manifold/plenum vacuum is in no way connected to the cam covers.
Maybe I'm wrong but I thought the only way pressure gets to the cam covers is through the oil passages that lube the cams and hydraulic lifters etc.
Someone can hopefully she'd light on this.
Thanks

I'm thinking that's when the piston's on it's downward inlet stroke. But again I'm not sure either 

[dublin.jd]

Thanks Webby the Bear
Yeah but that's where the vacuum comes from for the brake servo and multi rams etc.
But I thought Breathers are for the crankcase, not cam cam covers. I know that if breathers are blocked pressure builds up in crankcase, and is transfered to cam cover through oil pressure. I doubt vacuum has anything to do with cam covers.
Again correct me if I'm wrong. Hopefully backing it up with info. At least i might learn something.
Thanks

[Entwood]

If I'm honest, I thought there would be positive pressure in cam cover due to combustion gases getting by the piston rings (albeit in small amounts) and that the pressure builds up only when the breathers become blocked. I don't see how there could ever be negative pressure in cam covers as the intake manifold/plenum vacuum is in no way connected to the cam covers.
Maybe I'm wrong but I thought the only way pressure gets to the cam covers is through the oil passages that lube the cams and hydraulic lifters etc.
Someone can hopefully she'd light on this.
Thanks

The breather bridge .. the big bit with ecotec written on it..... is connected to the plenum via the "top hat" seal (underneath) [lines 2&3 in attached picture]... so vacuum in plenum = suck in breather bridge = suck in breather pipes at the rear of the breather bridge= suck in breather box to which those pipes are attached = negative presure in crankcase to which the breather box is connected.

There are also two pipes in the breather bridge that go forward to the throttle bodies [lines 1& 4] which will also get a suction effect from the TB's

If ANY of those pipes get blocked .. and the air movement (or "suck" if you prefer) (then blockage if it occurs) comes from the breather box up into the plenum ... not the other way round ... any of those pipes, or the airways in the plenum bridge (which are a tad small) get blocked and the breather system stops working, then the pressure builds up.

[Sir Tigger KC]

How likely is it that the breather box itself might get blocked up? 

So the breather pipes and the breather bridge might have been thoroughly cleaned and you think all is well, but unbeknown the box is still blocked causing the dreaded build up of pressure..... 

[omega3000]

How likely is it that the breather box itself might get blocked up? 

So the breather pipes and the breather bridge might have been thoroughly cleaned and you think all is well, but unbeknown the box is still blocked causing the dreaded build up of pressure..... 

Ive had one blocked solid , just poking the crap down to clear the breather box entries wont clear what crap is in the box itself if its really bad .

[Webby the Bear]

How likely is it that the breather box itself might get blocked up? 

So the breather pipes and the breather bridge might have been thoroughly cleaned and you think all is well, but unbeknown the box is still blocked causing the dreaded build up of pressure..... 

Ive had one blocked solid , just poking the crap down to clear the breather box entries wont clear what crap is in the box itself if its really bad .

Maybe a job to be included on a new Omega purchase then? 

[dublin.jd]

Entwood, thanks for taking the time to explain that so well. and I see what ur saying. But don't see how the pressure in the crankcase is related to the cam covers other than through oil pressure? and not vacuum.
Again I'm keeping an open mind.
Thanks

[05omegav6]

Higher crankcase pressure forces oil out through any gaps/weakspots. The higher the crank pressure, the more oil gets forced out. Absolutely nowt to do with oil pressure

Blow through a straw into a full glass of water and watch what happens...

[dublin.jd]

If I'm honest, I thought there would be positive pressure in cam cover due to combustion gases getting by the piston rings (albeit in small amounts) and that the pressure builds up only when the breathers become blocked. I don't see how there could ever be negative pressure in cam covers as the intake manifold/plenum vacuum is in no way connected to the cam covers.
Maybe I'm wrong but I thought the only way pressure gets to the cam covers is through the oil passages that lube the cams and hydraulic lifters etc.
Someone can hopefully she'd light on this.
Thanks

The breather bridge .. the big bit with ecotec written on it..... is connected to the plenum via the "top hat" seal (underneath) [lines 2&3 in attached picture]... so vacuum in plenum = suck in breather bridge = suck in breather pipes at the rear of the breather bridge= suck in breather box to which those pipes are attached = negative presure in crankcase to which the breather box is connected.

There are also two pipes in the breather bridge that go forward to the throttle bodies [lines 1& 4] which will also get a suction effect from the TB's

If ANY of those pipes get blocked .. and the air movement (or "suck" if you prefer) (then blockage if it occurs) comes from the breather box up into the plenum ... not the other way round ... any of those pipes, or the airways in the plenum bridge (which are a tad small) get blocked and the breather system stops working, then the pressure builds up.

Ok I've read all that again and came to the conclusion that adding pressure relief valves to the cam covers would be beneficial. At least til the breathers were remedied.
Does that make sense?

[Entwood]

Entwood, thanks for taking the time to explain that so well. and I see what ur saying. But don't see how the pressure in the crankcase is related to the cam covers other than through oil pressure? and not vacuum.
Again I'm keeping an open mind.
Thanks

The oil pressure in the cam covers is zero .. oil pressure ONLY exists in oil ways, drillings, pies etc .. once the oil is sprayed onto a surface, like a cam lobe, the pressure is zero.

Within the cavity that is the cam covers/crankcase there is only air pressure, this increases with the effect of gas blowby from the compression/combustion pressures leaking past the piston rings, and is decreased by the effect of the breather suction we are discussing. The actual "atmosphere" within the crankcase/cam covers cavity comprises a mix of blowby gases/oil mist/water vapour.

If the pressure builds up due to blocked breathers, we know the cam cover gaskets are the weakest link, so they fail and leak the "atmosphere" from within to without ....   the blowby gases will simply escape, the water vapour will evaporate fully, the oil mist will condense and stick to any surface it can, then run and appear as a leak. If the cam cover gasket hole is large enough some of the lubricating oil spray from within may well leak out directly through that hole.

The answer is to maintain the slight negative pressure that the "vacuum" from the plenum causes via the breather system, this will "suck" the "atmosphere" out along the breather pipes until it gets burned back in the cylinders ... unfortunately for us .. the temperature change from a hot crankcase to a cold(ish) plenum cause the oilmist to condense as the horrible emulsified mess that we get, that if not cleaned out blocks the airways we want to do the job !!