Hello all - I've been reading these very helpful forums for ages but this is my first post so a) hello, and b) please be gentle :?

A bit of background: I'm not a mechanic, but I know which end of a spanner is which and I'm not afraid to take cars to bits to fix them. Having said that, I have taken a back seat with my current car and haven't done any major work on it (because I've never needed to). I've owned Rover 200s and a citroen zx in the past (for my sins) so I've spent a fair bit of time tinkering under the bonnets of those, but as far as the guts of a Focus goes I've got very little experience.

I have a 1.8 56-plate TDCi Zetec with about 83,000 on the clock (I've owned it since 32,000) and a few months ago I lost boost from the turbo. It had been working perfectly before then but one day I went to drive to work and there was just no boost. I checked the intercooler pipes and there were no leaks. After lots of faffing and checking and re-checking the pipework I could get to easily I eventually bit the bullet and took it to my local garage who changed the MAF sensor and the air filter to no avail, and then ended up charging me 300 quid to clean a load of crap out of the turbo :cry:.

Since then it has been boosting fine, but about three weeks ago I noticed a loud hiss from under the bonnet. This time there was a leak in the intercooler pipe quite near the turbo, which I sorted myself (quick swap job).

It has again been sine since then - the noise went away and has been boosting well - until over the weekend I drove 200 miles down south. About 10 miles from the end, with no sudden horrible noises or bangs, I lost the boost again - same symptoms exactly as the first time there was a problem. There is no hiss, no smoke, no juddering or clanking, but there is a bit of a blowing noise (sounds a bit like when the back box went on my old rover, but not as loud, and I can't locate it from outside the car with the engine running). I ended up limping home with no boost and when I got home it smelt a bit, well, exhaust-y (I can't really describe it any better than that).

There's still no smoke, noises, judder, overheat, lights on the dashboard, errors or fault messages and no appreciable loss of MPG, there's just no boost. If I really push it past 3000 rpm in third and then take my foot off to change up I can hear the turbo spooling down slightly, but it doesn't sound like it's doing much.

I'm damned if I'm spending another 300 quid for someone else to do a bit of work on it that I could do myself. I'm prepared to do whatever it takes and I was going to strip down the turbo but since I don't know where to start with this car, before I break out the Haynes and start taking out a million bolts chasing down something simple that I've overlooked I thought I'd ask you good people if you had any bright ideas. Even if it's not something simple, if you could suggest something horribly complicated I'll give it a crack!

I'd be really grateful for any help or suggestions you might have.

Thanks.