Temp gauge & Fuel gauge problems

[LES HARDWICK]

Temp gauge barely moves up [about ¼ of an inch] nowhere near “180” I tried the boiling water trick but the gauge never moved at all!
 
Fuel gauge only reads ¾ full on a full tank of gas? Check sender, out of the car seem to read “full and empty” fine! Question: what is the black plastic flat box in the trunk on the port side of the car, with all the plastic pipes running to it?

Thank Les
'71 280SL

[J. Huber]

Hi Les. I believe the black box you refer to is your fuel expansion tank. Mine and others w/230SLs reside "starboard" but they are generally the same. They allow for some breathing as the fuel tank does its thing. One of the three small tubes should lead to the notable FSVT (funnel-shaped vent thing) below the rear valence.

James
63 230SL

[Jonny B]

Les,

James is correct about the vent breather, but on the 280 the famous FSVT is no longer present, with the increased level of smog control, the tank no longer vents directly to the atmoshpere as on the older cars.

Did you check the entire length of the temperature gauge, as this is a single sealed unit. It does not take much of a crimp to damage the device. They are repairable, but not as a do it yourself kind of thing. There have been a number of posts on the temp gauge and on the gas gauge. Use the search feature for the "General Discussion" items and you should be able to find a lot of information.

Jonny B
1967 250SL Auto