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[GastronomicKleptomaniac]

 Right, this is my first how-to, so be gentle... but here's a guide to changing the heater bypass valve, commonly called the HBV. Well known for failing on the Omega, resulting in coolant dribbling from the rear of the engine, onto the floor. Symptom in my case was stopping at a set of lights and steam issuing from the offside rear of the bonnet... I think my exact words were "oh dear". (If someone can do a more comprehensive list of symptoms, I'd be grateful... )

 The part itself, to the man on the street, is about £33 including VAT, from Vauxhall. Obviously with Trade Club discount, its cheaper. I wasn't willing to take the chance with a third-party HBV... others may have, in which case they'll be able to advise re: thumbs up or down.

 For the most part, you don't need any mechanical skill, it's purely "twist, pull, etc". For actually swapping the valve itself, however, being on first-name terms with Mr Tickle would be handy. I'm not, and so ended up getting my mechanic to do the actual swap of the valve... this guide covers removing everything up to that point.

First, a bit of H&S advice. There's not too much to cause damage, but obviously there's a few little bits. First of all, make sure the car is cold when you do the work - draining coolant when its hot will a) burn you, and b) most likely damage the engine.
 Right, now, I always wear overalls if I'm working on the car. In this case, there's not much to messy or injure yourself... but it saves getting your clothes dirty when you have to crawl under the car to retrieve a clip or tool...
 A decent barrier cream is recommended - stops any grease, coolant, etc, getting into your skin. On top of that, I'd be wearing at least vinyl gloves, and then I wore a pair of fabric gloves. I have big hands, which are liable to getting cut and scratched, and they protect nicely.

 Guide will be in the next post.

[GastronomicKleptomaniac]

Right, this guide is for a 2002 (thus facelift) MV6 - I'd imagine its broadly similar for prefacelifts.

 First, the essential parts of a good mechanic-ing session - the car (oddly), a tool kit (thats my spangly new Halfrauds 150pc set... I'd also add a few different pairs of pliers and a set of flat screwdrivers). And a cup of tea. (I recommend a kettle and either a minifridge, or a tub of "coffeemate", in the garage. I use Asda's own teabags, they're excellent value and do make a good brew. Milk is full fat.)
 I did this on my driveway (since my car won't fit in the garage) - you only need access to the front end.



 This is the new part - so you know what you're after. The vac pipe is behind my thumb (arrowed, for some reason), there's the other three pipes... and that's it.



Pop your bonnet, you'll see something vaguely resembling this... We're working in the offside rear off the engine, and once or twice at the front.

 First, you need to drain the coolant - I usually use the radiator bottom hose. (Those with an eye for detail will notice than my header tank remains full throughout the guide... it really should have been empty, but some fool forgot to drain the coolant first...)



 To remove the wipers, get a small flat screwdriver into the grooves on the caps, indicated here -



You'll see the following 13mm nut - needs a socket and ratchet to remove. A good WD40ing before attempting to shift it is always welcome. Then a quick tap on the end of the ratchet starts the undoing, the nuts aren't particularly tight. This job is a bit if a swine... if you flip the offside wiper off the screen, then grab the stubby horizontal bar and wiggle it off... might be worth levering under with a large screwdriver, taking care not to damage the screen or paint. I, being a brute, just pulled it til it let go.
 The nearside wiper needs a bit more work - opening and closing the bonnet to get it in and out... same applies - jiggle it with a bit of force til it releases. (There's probably a much better way to do it, but I've not found it yet). It can help if you remove the nearside wiper blade, and put a lump of thick sponge over the end so as not to chip your screen... makes removal and refitting via the underbonnet gap a bit easier.



 There large rubber seal running across the front of the scuttle simply pulls off - rewmove it fully and put it somewhere safe.. and clean.

 Now, to get the scuttle off, there's a Torx screw on the offside to remove - I used a T20 bit since it fitted. Again, it's not particularly tight. Take this out and put it somewhere safe.



 Now, we need to get under the windscreen seal, as indicated below. To do this, I slid a small screwdriver underneath, levered it upwards, and held it with my left hand.



 This enables us to get at the clips holding the scuttle on. There's about half a dozen, all across the bottom of the screen... they all need to come out. They are easily removed, use a large flat screwdriver, turn through 90 degrees, and they let go. They look like this -



 Now, the nearside scuttle unclips from the offside half. Once the clips are out, it just needs a gentle wiggle from side to side, then easing out from the other half. This can be simply laid up out of the way, no need to detach the washer jets and piping...



 ... Then manouevre the "big half" of the scuttle out, again, it can just lay across the engine bay out of the way... the HBV's approximate position is shown by the red arrow.



 Removal of the scuttle allows some access to the HBV. You can see it in this picture (my camera would fit, my head wouldn't), you need to remove the vac pipe (and tie it up or rest it somewhere on top of the engine) - then the fun job of removing the large hoseclips. You can get special hoseclip pliers, or use a pair of large angled nose pliers. Make note of which pipe goes on top and bottom (anything from Tippex to a piece of string around the top hose)... then ensure the swear box is to hand.
 Remove the pipes, take the HBV out of the engine bay... then to misquote Mr Haynes... fitting is the reverse of removal...



  Remove the pipes, take the HBV out of the engine bay... then to misquote Mr Haynes... fitting is the reverse of removal...

 It should all go together fairly easily - just make sure everything is lined up, don't force anything plastic... and for the wipers, trial-fit them, and check they're not going to catch each other when in motion. Top up the coolant with the correct ratio of antifreeze and water, and bask in your newly functioning, on-leaking heating system.

 

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 Right guys, thats it. Any thoughts, improvements, "you could have done this like that" would be appreciated.

Regards
Pete