Cadillac STS Forum - 2005 through 2012 Discussion, N* Losing coolant in Past Cadillac Vehicle Discussion; I am getting a "coolant low" message about every 1-2 months. I see no evidence of leaks on the engine ...
Mines is leaking also but I see big puddles under my car sometimes or I smell the sweet smell of coolant burning off. Never get a low coolant message or never run hot. It only leaks when I add into the resevoir. I don't understand. During the winter I have no heat unless I add coolant and It slowly leaks out. At times it leaks massively.
Members haven't reported any head gasket issues like the pre-2005 STS but water pump issues aren't uncommon. Earlier model years are getting to the age that AR owners consider replacing all hoses. I bet they are OK.
If you garage the car and notice that sickly sweet smell, I'd bet on a leaky pump. I had one that left a puddle at about the firewall.
Mine got a new water pump at ~50kmi for this reason... I never noticed fluid on the ground, or smelled antifreeze, but every so often the light would come on and I'd check the reservoir and it would be low. CPO warranty ftw... Dealer claimed it was a $700 fix.
Automobile(s): 2005 White Diamond STS N* 1SF RWD ACC/HUD
Re: N* Losing coolant
Just had my water pump replaced at 103K miles. They also had to replace the crossover gaskets. Still leaked when I got it back...turned out to be the thermostat housing o-ring. Nice to have a new pump too, however. This was fixed under my extended warranty.
I got a new water pump and thermo housing gasket @ about 65k or something. Fixed my issue. Dealer did a pressure check - you could see the evidence for the thermostat housing leak, but the WP was a surprise. The level in the reservoir hasn't moved since then thankfully Mine smelled pretty strongly of anti-freeze at the time I had it repaired, but the leak was like adding a pint a week or something (driving ~350 mi/week).