My Cab has been reluctant to start in the cold recently and has been producing clouds of white smoke. It has started every time, but I suspected the Glow Plugs needed refreshing. I sprayed on some penetrating oil on Friday, then again on Saturday when I dismantled enough to get good access to the plugs. I had read about them breaking, so took it slowly and carefully. They were all very tight, but came out successfully. I had a bit of trouble getting one back in.. It didn't want to screw into the thread, I ended up screwing one of the old ones back in and out before the new one would go in. I cleaned out the inlet pipe as well, I didn't have the time to clean the manifolds and EGR valve, I'll maybe get to that another time. My wife came out with a cup of tea and I showed her the sooty gunk in the pipes. She said I shouldn't expect an improvement as the kettle gets scale in it and that doesn't stop it from working. It's been flipping cold and with the new plugs it starts immediately with no smoke, so I'm very pleased.