Hello Jlo - search the XJS section for “cooling system temperature readings” and you should get a post from Sept. '02 from a lister in Australia (at the beginning of the post) that posted some temp readings, using the gun, from before, and after, water pump repair on his "88 V12 - Tex Terry, II - 1991 XJS V12 Classic Coupe, 1986 XJS V12 coupe - 3/29/2020 0059hrs. EST USA