I purchased a replacement 1.6HDi Citroen Xzara Picasso engine. A mobile mechanic transferred all the ancillary parts from the previous engine onto it and fitted it to the vehicle. After less than 500 miles (having run it gently to 'run it in') the noise of big end/main bearings suddenly occured. The engine was extracted and sent back to Direct Engines UK Ltd (the supplier) with the turbo, cooling and fuel system in place for their inspection. They are now claiming that the cause of this catostrophic failure is silicone gasket particles used by my mechanic, blocking the oilways that supply underside of the pistons and the crank bearings. They said silicone should never ever be used on these engines but my mechanic (who admits to having used some silicone on this engine) claims he has used silicone to bolster rubber gaskets etc for the last 30 years with no problem. Are the engine company simply trying to avoid blame for a poorly assembled engine?

Paul Lumsden, January 2012

I dont know about the citroen, but I did a Freelander Rover K-series engine head gasket change and on that engine youdefinitely will have problems if you use anything but the recommended sealant. The reason is that some of the oilways are formed by a groove in the head where it bolts to the crankcase, this groove then effectively becomes a tube and conducts the oil around the system. If you use silicone you might get excess sealant squeezing into the oil way and setting. Result? oil starvation and bearing failure. The sealant used on the freelander is Loctite 574. This sealant sets when it is deprived of air (it's anerobic). Any excess squeezed into an oilway stays liquid and is flushed out by the first flow of oil. I suspect your problem has arisen for similar reasons to what I have described.
Hope this helps
Steve

Steve Jones, January 2013

silicon is a diy fix imho

Steve, January 2012