Subject: Re: V12 Boiling
An old post, but I might as well add my two pennorth! Peter...I used to have much the same problem with mine. I thought mine was boiling...but then I realised water was blowing out of the radiator cap even before the engine was thoroughly warm. My engine was pretty worn...bores quite worn, & many piston rings broken. In fact the problem was that the crank case was being pressurised from blow-by past the pistons passing the (pretty non existent) pump oil seal & carbon seal, raising the water pressure & thus blowing it out.
I did replace the carbon seal, which improved things, but obviously not a complete cure. I was driving back from a club meeting one night...actually drove past my home as I was enjoying the drive. 100mph on the A3 (no 50mph cameras in those days!), all fine...then suddenly a fountain of brown water from the radiator, which took several seconds for the wipers to clear. I had to remember the curve in the road as I couldn't see a thing...worrying at that speed! Fortunately 3 lanes to play with & not much traffic about.
Incidentally, unlikely your impellor is corroded, it should be bronze...if there is a problem with the pump, it's far more likely to be corrosion of the aluminium housing...Lagonda's aluminium seems to have been pretty poor quality.
Laurence