Further to past correspondence on turbochargers clogging up, especially those with variable vanes, I was in the local Jazz Club last night and was given some rather doubtful advice. Whilst very original in thought, it somewhat horrified me, and will I expect you also. The “expert” in question said don’t use any of proprietary cleaners, just drill a suitable diameter hole in the turbine housing then drill tap it to M8 size. Then squirt in plenty of caustic soda based oven cleaner, screw a very short bolt into the tapped hole, and just leave it overnight. The next morning just start up the engine as usual and the vanes will have been unclogged! My thoughts are what if (via the EGR system) the solution were to get into the combustion space? Surely there would be corrosion to the top piston ring land? What happens to the solution going into the catalytic converter and, if fitted, the diesel particulate filter? What happens about small metallic particles going through the exhaust system? I hope that this did not put you off your dinner! Whilst it maybe might have some merit in extreme circumstances, such as in a war zone, I somehow do not think any manufacturer would approve!
Bob Fisher

Good God! Do they still have jazz clubs? I thought they all went out in the last century! No, your note didn’t put me off my dinner Bob, but I’m sitting here rather agitated, with half my radiators off, for some strange reason – probably one of the two solenoid water valves has gone down – and the allied air forces are doing their very noisy F15 fighter training in the skies above us. Yeah, well that oven cleaner trick might be alright for a ten-year old Golf that’s worth peanuts and not worth repairing, but it’s not something that you would do with a half decent car, is it? That has set me off wondering when the first variable geometry turbos arrived, which my research discovered to be the 1991 Fiat Croma, a model which, five years earlier, had pioneered the direct injection turbodiesel in cars. Of course we didn’t get that Croma diesel in the UK, but it’s gone, but not forgotten, which was rather less forgettable than the later Croma.
Doc