i have a 88 240DL i recently replaced the upper and lower radiator hoses and upon first start up the temp gauge will run normal then spike up for 25 seconds then go back to normal what would cause this i did order a new thermostat last night

 

probably the compensator circuit thing on the temp gauge is out of whack, totally coincidental to your work

 

Give the dashboard some acoustic tuning (smack the crap outta it) and see if any change. My temp guage is flaky right now after cluster swap. Could be that I lost tension on the pins for comp board. I pulled it. Worked fine before. Havent even put a temp guage on the engine because I know its fine.