I have 86 sport trim that I am working on restoring and when trying to work out the coolant system I discovered I may be missing a tank. I have the overflow tank that mounts on the driverside behind the radiator next to the battery but I think I may be missing the tank that mounts next to the passenger headlight, however some sources I've read that the early models did not have this tank, does anyone know if I need to find this tank. Thank you in advance for any help.

 

I am not familiar with the early S4 setup but I would think you only need one overflow tank. So if properly setup I think you should be good with the one you have. Even if it had two to begin with I'm sure it could be setup to use one like the later S4 and S5 cars.

 

passenger tank by the headlight is for the windshield washers on an FC. the FD uses that spot for the coolant overflow

 

My 1987 S4 non turbo only has the single overflow tank between the radiator and front bumper. Have not ever seen a tank on the drivers side. behind the pass headlight is a windshiled washer bottle, and mine has the stuff for the cold start injection, but I run megasquirt, so it is unused. Only keeping it there for a plan to run premix to an aircraft OMP in the future so I can run synthetic in the future

 

There are two setups with different overflow tank locations. Either in front of the radiator or driver side near the leading coil. You only need one.