My Omega 2.5 V6 is loosing water very slowly and i can see that there is a bit of a weep by the Heater by pass valve.

How much are these normally and where is the best/cheapest place to get one?

I realise that changing it is likely to be entertaining.

Thanks Darryl

I changed my HBV yesterday as it happens - mine had cracked and started to leak badly. I believe they're about £30 from Vauxhall, so not bank-breaking.

I was expecting an absolute swine of a job, but actually it wasn't bad AT ALL. The most fiddly thing was the spring-clips on the coolant hoses. There are three coolant hoses on the HBV, and one vaccum pipe on the top - that's all there is to change. It took me about 30 minutes for the HBV, and maybe 15 minutes taking the scuttle on and off - so allow a good hour or two to take your time.

To improve access, it's an extremely good idea (if not a requirement) to remove the wiper arms (2 nuts) and the scuttle - this only takes a couple of minutes and is well worth it. For more detailed info on removing the scuttle, see Cipher's post on changing the dis-pack in the common tasks section - it describes the process well.

Anyway, back to the HBV, once the scuttle is off, get yourself a good pair of adjustable grips, (I used plumbers grips), and take off the hoses on the valve one by one. It's easier to remove the drivers side ones first, and then the single hose on the other side. Don't be scared to use a little bit of "persuasion" to manouver the HBV/hoses a bit, but do be careful not to strain anything either.

Then, as Haynes often quote - "refitting is the reverse of removal".

You'll find (or at least I did) that it's a lot easier than it looks, and it's possible to manouver it to such a position that the hoses can be easily removed and re-installed. All you need is a little patiance and a steady hand for the clips!

I've just flushed my coolant and renewed my antifreeze - the old stuff was brown thick and nasty, so not before time. I'd recommend a coolant flush as well if time/funds allow. 50/50 antifreeze mix every time for me.