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Ive read a lot of posts saying this should be changed when servicing as it has a habit of collapsing.

Where does this live and is it a simple part to change ?

What symptoms would a collapsed valve give ?

[i]Dont know if this helps:[/i]
1.8 petrol its at the front look at the thermostat housing above or next to it is a rubber hose a small one leading to the front where the manifold is it then attatches to the pcv valve which is in a rubber holder simply pull this out and thats the valve its the hose that has a problem with collapsing if you follow it round to the rear of the engine it bends and goes into the throttle with the engine running give it some gas and see i the hose collapses the pcv valve spring does go weak
In my 1.6 it's located just underneath the battery box.

If it collapses you'll usually get an engine light on with an error code. Not all the time though. Also, when you open your fuel cap, you'll hear the tank depressurising. The PCV is supposed to get rid of vapourised petrol that builds up in the tank, and if it fails, then it all just stays in the tank and leaks out with a depressurisation noise when you open the cap.
Thanks arti ,gsm and btmaldon that will be very helpful when I have a look. I was hoping to have a poke around at lunch but the heavens have opened up here badly.

arti you are a walking focus haynes hehe.

the fuel system is supposed to operate under a partial pressure so you should get a small hiss and has nothing to do with the fuel tank
The blow by vapors that end up in an engine's crankcase contain moisture as well as combustion by products and unburned fuel vapors. The crankcase is sealed to prevent the escape of these gases into the atmosphere, but the vapors must be removed to prevent oil contamination that leads to sludge formation. The positive crankcase ventilation (PCV) system siphons these vapors from the crankcase and routes them into the intake manifold so they can be reburned in the engine.
The main component in the PCV system is the PCV valve, which is usually located in the valve cover. A hose connects the PCV valve to the intake manifold. A second hose between the air cleaner and crankcase or other valve cover (V6 or V8 applications) provides fresh air to help flush the vapors out of the crankcase. Some engines have a separate air filter for the PCV breather hose located inside the air cleaner.
The PCV valve is a spring-loaded valve with a specific orifice size designed to restrict the amount of air that's siphoned from the crankcase into the intake manifold. This is necessary because air drawn through the valve from the crankcase has a leaning effect on the fuel mixture much the same as a vacuum leak. So air flow through the valve must be controlled within certain limits. At idle, air flow is reduced because little blowby is produced. When the engine is cruising and vacuum is high, airflow through the PCV valve is at a maximum to purge the blowby vapors from the crankcase.
It's important to note that PCV valves are sized for specific engine applications. The wrong PCV valve for an application can flow too much or too little air causing driveability problems. Varnish deposits can clog the valve, so replacement for preventative maintenance is recommended (every 50,000 miles usually).
when opening the cap the 1.8 is as said open the bonnet in fact hold on ill get a picture up

okay heres the pics
When you said PCV I thought you meant Purge Control Valve... seems I might have been talking about a completely different thing.
Lol positive crankcase ventilation valve you get them cheap enough on ebay the hose though is a ford job but less than 10 if you do need the hose a good tip is on the bend right up to where it goes into the throttle body wrap around 6 layers of tin foil that stops the heat softening the rubber which causes it to collapse
Thanks arti,

that was an excellent guide. The PCV had collapsed managed to change it, added the foil aswell, working fine now.

*thumbs up*

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