Finally got around to changing the glowplugs on our recently acquired
306 D Turbo, which was becoming a total bitch to start in the mornings.Bought a complete set as I couldn't be bothered to test them. Did cylinders 1-3 in about 40 minutes (2 was tricky due to the pump being in the way, but not horrendous). Removed plug 4, went to fit the replacement and it did half a turn and went tight. Paranoid about cross threading it, I removed and refitted it (repeat about 30 times) and couldn't get it to go in. Checked the threads on the head which looked clean, refitted one of the old plugs (not the one that came out of that cylinder) and it went in no trouble. In the end, I tested the old plugs, found two good ones and fitted one of them into cylinder number 4.
Comparing the thread on the new offending plug with the old plugs, it looks absolutely fine, the new plugs came as a set of four and were all the same type (Halfords own - was all I could get). The car has four good plugs in it now, and it starts perfectly, so the job is done, but I'm confused as hell as to why the plug wouldn't go in. Anyone seen this before?
Dan