I have changed the water pump on my '98 V8 BMW (the one with the ally block) this afternoon. 'tis all done now, but I have a problem.

As I finished flushing through the cooling system I went to put the drain plug back in the bottom of the radiator and it snapped. It's only plastic, and came out OK. Trouble is the main dealer / parts shop are both closed now. Which means I can't get a replacement until Monday.

It goes into a plastic end cap on the radiator, and has a rubber o ring just off the shoulder of the bolt, and a crush washer on the face. I have managed to find an M10 set screw which fits, and I have put that in as a temporary repair (with an ally crush washer). But I've only had the confidence to do it up finger tight. It holds water, but I'm not sure it's a long term solution.

So question is, with the cooling system full of fresh water will the engine start corroding between now and Monday.

Or do I fill the engine with the recommended 50/50 mix antifreeze and then drain it back down on Monday night, when I can get the new plug fitted?

Cheers
Mike

Between Now and Monday you shouldn't have an issue with corrosion.

Go to Halfords and buy a few bottles of de-ionised water. You should be using this anyway instead of tap water!

personally i would have thought in the long and the short of it, it will be perfectly OK, its not not goin to turn into a lump of oxidized alloy that quick, that takes years, i would how ever suggest tightening the bolt up a bit more as the coolant system is a high pressure system which if the bolt isnt tight could cause incorrect loading on the plastic threads on the rad and rip them of, doesnt need to be all that tight but tighter than finger tight