Today i was driving to get new tires and everything was fine. As i pull into the bay the tech says your car is leaking coolant bad. So i look under to find almost all my coolant pouring out from the bottom of my car. (i dont have the skid plate on the bottom) I lift the hood trying to see where its coming from and all i see is water boiling/bubbling inside the reservoir but nothing else. So i drive my car home (less than 2 miles) watching the temp gauge as it stays at normal temp with no issues. I get home and refill my reserviour which was empty and start her back up to figure out where the leak was coming from but nothing. The car wont leak anymore, so i drive around town to see if it warms up and the temp gauge begins to fluctuate a little, which made sense because i probably have air in the system. I didnt bleed it. but my question is what the heck would cause this? im reading all kinds of threads about blown head gaskets causing this and its making me nervous as my car has only 91k miles and has never had signs of overheating...Thanks

 

Get under the car and check the rubber tube that goes to the radiator. It'll be on the right side bottom when you're facing the engine. Check all those rubber tubes that are related to the radiator assembly.

 

Pay close attention to temps, but don't panic just yet; it could just be a bad radiator cap. (hoses or thermostat are a possibility too)

Do be sure and bleed the air out of your system even while your trying to figure it out though. Don't drive around like that.

 

I'm trying not to panic lol but I don't understand how all the fluid would pour out like a hose busted but now it won't leak at all?

 

is it time for a coolant change? if so, the shop can do a pressure on your cooling system.. shouldn't cost any extra while your car is in for a cooling service.

 

Caps do go bad. If your cap isn't holding pressure consistently, then it will allow a lower boiling temp and hence, boil over; which flows into the overflow reservoir until it eventually overflows from there.Just to ease your mind, look at your oil on the dipstick, is it milky or frothy or have any white in it? Next look at your coolant in the radiator (when it's cold), is there frothy, milky goo in there? Any of those would be a sign of mixing coolant and oil (ie bad head gasket). Also, if your HG was bad, you'd quite possibly be throwing a misfire code too. The best way to cover you butt 100% is to have the cooling system pressure tested.

 

The cap replacement interval is every 30k.

Radiator dump/fill w/hoses every 60k.

I would see where it is coming from, first.

 

Also check the bottom of the radiator where the metal is crimped onto the plastic. That area can leak too, you will see a trail of coolant.

 

That's good to know because I havent changed the cap since I got the car with 40k miles. I'm going to go get a new cap. How much coolant is needed for a full flush?

 

I dont see how these can go bad when its just a cap? I am coming up on 45k for my cap amd so far pretty good.

 

Thing is it won't leak anymore I bled the system and haven't been able to get it to leak again. No bad hoses or radiator leaking. The only thing I can think of is if it poured out from the over flow tank

 

Could you find a trail of where it was leaking from? It would only flow from overflow tank if too much coolant was in it. Strange to have a big leak (where it's on the ground) and then not have one a day later!!!!

Caps don't seem to go bad very often.

 

Nope no trail at all. While it was leaking I lifted the good and all I saw was the tank bubbling like there was a jacuzzi inside of it lol. Drove it home immediately after and my temp gauge was fine. So maybe there was too much coolant?

 

I don't believe it actually says that. I'm pretty sure it says to check them every 30K, doesn't it?

 

It's not JUST a cap though. It's essentially a calibrated, spring loaded, pressure relief valve. They do occasionally go bad, and they can wear out over time. If they don't hold enough pressure, your system will boil over at a lower temperature than it should (remember the ideal gas law from chemistry/thermodynamics? PV=nRT ).