Forensic Investigation – Early start with a long list of things to look at to try and establish the cause of the overheating problem, I discussed the problem at length with Chris (Model A entered in P to P) First job was to find the radiator of the 29-27 Sedan, this took a while and a climb up onto the racking in the workshop. I spent a while back flushing it and cleaning it up and then ran several tests to check how long it took to drain from full, I then carried out the same test on Benson – this proved fairly conclusively that there was no blockage in Benson’s rad – it drained quicker than the original rad from the Sedan. Next check was to try and check if the water pump was circulating coolant properly around the engine, image to the right shows part of this test ! This test showed that the pump was circulating the water, but not steadily, it would gush and then do nothing for a couple of seconds and then gush out again – I thought I was onto something so rigged up the same test with the electric water pump – but saw exactly the gushing with the electric pump. I stripped down the mechanical pump to double check there was no issue with the impellor, all seemed OK so reassembled, regreased and refitted to the car. Refilled coolant after check of “shop manual”, should have taken 16 litres, but only took 14 to overflow the rad, I siphoned off 1 litre so that the level was just above the core. Ran the engine for about an hour at different revs and took hundreds of temperature readings around engine bay with infra red thermometer. Carried out a block test, which indicated no exhaust gases in the coolant. The car did not overheat and a quick look at the data suggests the temperature gauge over-reads by about 10 degrees.