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What Is This Tubing And Should It Be So Easy To Clip Back?

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Hi all,

I am a new joiner to the forum, and having previously put 188k miles on a mk1 focus with very little hassle, I'm after a mk2.5 at the moment as a second car.

I went for a test drive yesterday and had a good poke around. 2009 plate, FSH, 59k miles on the clock seemed to be running very well. However, when I stuck my head in the engine bay, some tubing, which runs from the top of the engine and down to the right, was disconnected at one end. It was easily shoved back on to where it came from, however I have no idea what it is or if it should have even come off / gone on so easily.

I've attached a pic of a similar sigma engine highlighting the pipe in question, so any help would be very much appreciated.


As a side point, the car only comes with 1 remote key (and no other key). I assume if I wanted another, then it'd be a trip to the dealership and c.£150 outlay?



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Ah, after wasting more time that I thought possible on google, it appears to be a breather hose and is no biggie just to clip back on.

Good news!



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The tubing looks like it is a breather hose, it connects between the rocker cover and the engine air inlet, it is a sort of emmision control thing and is often diverted on a race car, thus why the car run ok with it disconnected, with it properly diverted (with a lotal loss system or a catchtank, and the inlet end blocked) the engine will run better

The engine crankcase has to "breathe" to release build up of pressure due to the air expanding in the crankcase and piston blow-by and to release gasses/ oily spray - these gasses are "burnt" so contain carbon monoxide and other harmful stuff, that is why it is diverted back into the inlet to be ingested by the engine, to prevent pollution to the atmosphere/ enviroment

On a race car the breather is diverted into a catchtank, this is to stop the warm, burnt gasses from the crankcase getting into the engine that also contain oily spray, the oily spray can contaminate intercoolers on a turbo (petrol or diesel), and spark plugs on a petrol the warm, burnt air takes the place of cool, oxegen-rich air, reducing performance (hence the reason the breather is diverted on a race car) the effect is realatively small though - a catchtank is also a safetey feature because it stops the oil spilling onto the track if the car goes on its side or roof, some tracks require a catchtank is fitted to prevent oil going on the track (especially if motorcycles rece there) so you need a catchtank to pass scrutineering

even on a race car you must be careful not to let the crankcase gasses into the (passenger) cabin, the breather outlet can even be directed away, under the car, and treated like an exhaust

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