Late last week I posted about rotten, stale reformulated (ethanol) gasoline that glued the valves into the valve guides on a 740T we had in the shop.

This was the fifth time this shop has had the problem with stale gas reacting in such a way that it turns into glue.

Apparently the common denominator is plastic or lined fuel tanks. You can literally reach into the tank and scrape this molasses-like sludge from the sides of the tank. The same, I believe, as with this particular 740. The results are the same--total intake valve seizure leading to timing belt stripping. Not a huge problem on a B230 engine, but certainly a disaster for a crash engine. There are no deposits on the cylinder walls or the pistons themselves, which pretty much rules out byproducts of combustion causing the problem.

Also, while carb cleaner removes the gluelike stuff from the valves, it also re-deposits the sludge when it evaporates. Therefore it's necessary to wash the head out with carb cleaner, not just spray the stuff off.