Wow that is hot !
I have one of these cheap fridge sensors fitted. For £3 I consider it disposable , and cant be highly accurate , but I dont think it needs to be. I pushed the thermocouple into an electrical spade tag clamped by one of the bbox mounting bolts , ran the cable down the transmission tunnel and out near the gear level , so have a real time view of the temp. The blurb says it will go up to 110 - if it goes higher and self destructs, at that temp there is something very wrong with the box.
I also have one fixed to the oil tank under the bonnet, with the display on the dash, to get a real time view of engine oil temp.
http://www.ebay.co.uk/itm/FOR-FRIDGE-FREEZER-REFRIGERATOR-DIGITAL-LCD-THERMOMETER-TEMPRATURE-MEASUREMENT/171337562066?_trksid=p2047675.c100009.m1982&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140328180637%26meid%3Dacd90c4552844619aa8f6ecb31020948%26pid%3D100009%26rk%3D2%26rkt%3D10%26sd%3D281083965381
