First off I checked the vacuum solenoid valve, which on the C5 is cunningly mounted neat the bulkhead in an almost inaccesible position
The original part seemed fine, but I fitted the replacement one anyway and took it for a quick drive - absolutely no difference in the symptoms.Checking the pipework with a vacuum pump proved that there were no leaks, and on releasing the vacuum you could hear the actuating arm/wastegate operating.
I next lashed up a pressure gauge, and had a go at measuring the boost pressure when the engine was revved. It immediately became apparent that there was a loud, and not very healthy noise coming from the general area of the turbocharger, and that the maximum boost was somewhat less than10psi - told you my gauge was a bit of a lash up....but the boost pressure should be around 1 bar.
The next job will be to get the car up on ramps and check the turbo to intercooler pipe running underneath the engine for leaks, but given the fact that just sometimes, at 3000+ rpm, the turbo will briefly come to life for a few seconds, it's starting to look very much as if the turbocharger itself is poorly.
All the more annoying given that the car has always had 6000 mile oil changes and has only covered 140,000 miles.
Has anyone ever changed a turbo unit on one of these engines... I know the one on the XUD could be a bit of a pig. Does the Hdi follow in this glorious tradition? Just for a laugh I cheked the dealer price for a new unit, and at over £1300 I think I'll investigate cheaper options!
