Ok i'm gonna try to explain this the best i can. I just got an fc for $500. It runs great but the other day i was driving it in my neighberhood( its not insured yet so i dont go far) and the coolant light went on and started buzzing. I looked at the temp and it was fine, but i had also just started driving. I went straight home and checked the coolant(which i had checked the night before) and it was fine. I called the guy i bought it from and their is a hose that runs from the radiater into the motor( the part of the motor is escaping me, you probably know what im talking about). This hose has another radiater cap on it and he told me to check it. It was dry so, he said to start the car and add fluid so i did. and it shot back at me cuz i put a little to much in i guess.sweet! So i shut the car off added some to the hose then started the car added a little more and drove it and the light came on again. About 6-8 hours later i started it up again, warmed it up, and right when i got to the end of my driveway it went on again so i shut the car off, checked the fluid, full, checked the overflow, full, and just put some in the hose with the car off. Then i drove it for about 10min before i had to go in and the light didnt go on again. Is this going to keep happeing, it seems like the fluid isnt getting pumped through hose. The temp on the car has never gotten high but ive never driven to far yet. Hope i explaind that good. Thanks!

 

Could be that there is air in the cooling system and as it "burps" out the air, the coolant level drops. Start the car up with the radiator cap off to bleed any possible air in the system. Also check for puddles of coolant under the car or on top and back of the engine under the upper intake manifold.

 

If your car is an S4, the 2nd radiator cap you're talking about is the stock location. Aftermarket radiators will have caps on them too sometimes, but you really only need one. I actually cut the one off of my aftermarket rad and welded a cover over it.

To bleed the system of any air, there should be a screw on the radiator (near the air filter box) that you can open up as a vent. Keep it loose enough for air to escape, but not allow tons of coolant to flow out. Now add coolant at the filler neck. You should see it bubble and eventually settle. When the level holds, tighten the screw and stick the cap back on the filler neck.

 

Thanks i will definitly do that tommaro.