temp. gauge problem

i had a company repair and re-install my speedo on the 58 century and they did a fine job except that now my temp. gauge dose not work. i checked my service manual, but i am not sure i understand it. it says there is a bulb that heats up and puts pressure on the sending unit. <BR>my questions are<BR>1. whats in the bulb?<BR>2. could the liquid (if any) in the bulb have leaked out while they had it apart.<BR>3. could the hose be bad at the gauge?<BR>the company will make good on it but neither i or the company have a clue as to what to fix.<BR>any clues anyone?<BR>thanks<BR>camman.8<BR>58 buick century 66r

Hi,<BR> The bulb usually has some low boiling point liquid such as alcohol or freon. The bulb is the liquid reservoir. As water heats up it heats the bulb causing some liquid to vaporize to gas thus increasing pressure in the small capilary line and the bourdon tube(the part of the system connected to the gauge) the increased pressure causes the tube to move cand through a little linkage move temp gauge, since the system volume is small it is very responsive. <BR> The bad news is the little capillary tube is easy to break at the bulb or at gauge.Once broke all fluid vaporizes.<BR> Good news is there are people in Hemmings under services offered who can repair this.<BR> Oh one more thing about the breaking the tube is small and sometimes of brass which gets brittle with age, if steel it gets rusty in which case "sneezing" on it can break it--- so don't go to hard on your mechanic!!