I just spent 2 hours on what should have been a 30-min thermostat replacement job. The reason? A damned T-40 bolt that's holding the thermostat housing to the block!!!

I stripped the torx head, and spent the next hour and 45 minutes on a dremmel, trying to grind a hex pattern into the round head. Much cursing and grinding later, I finally manage to break the thing free.

So what is the purpose of a Torx head? Are there any advantages for Torx over a standard hex head? Why are Volvo engineers so obsessed with these things? I hate them!

On a separate note, does anyone know the thread and pitch of that T40 bolt for the thermostat housing? The one I extracted is beyond mangled, and I'll replace it with a proper hex bolt.

Thanks