Lately it seems that my coolant is leaving the cooling system and ending up in the overflow bottle. I noticed the overflow looked really full the other day. Then I opened the cap at the thermostat neck and found that the level was pretty low. I siphoned coolant out of the overflow and poured it back into the system. Now, it seems to be doing the same thing again. No leaks anywhere.



Can anyone explain to me what's going on here?

 

theres a leak somewhere! the way that works is when the water expands it goes into the overflow, when it contracts it goes back into the engine. if theres a leak it can push the water into the over flow and then it wont make enough vacuum to suck it back.



have a close look at the water pump and the hose between the overflow and the engine, it also might be a radiator cap going bad too

 

Yah, my cap on the radiator is looking pretty suspect.

 

where was it on the night of the 11th! we have ways of making it talk!

 

Theres a plastic piece on the S4 filler neck that the cap threads onto. Under that piece there is an o ring that has gone bad on me. Check that too.

 

my 86 GXL was doign that same prob last week! but i replaced the cap and it stopped doing it, but also it says that my coolent level is low i have no clue what thats about, since the level is fine**shruggs**

 

the buzzer/light has a sensor in the radiator, not the over flow. make sure theres coolant in the engine, not just the overflow bottle

 

do you smell coolant in the exhaust?

 

Nope.