Hey everyone, I have a few problems that ive been having with my vehicle lately, and would really appreciate your guys expertise, as I'm no mechanic and would like to have these thimgs resolved ASAP.
First of all, a few weeks ago on my way to work, I noticed smoke/steam coming out out my hood, from the passenger side, and my car was overheating, I was driving on the freeway so I got off and stopped at a gas station to see what's going on.
The coolant reservoir was boiling, but just about empty, so I let the car sit for a few minutes, amd I filled it up with water and the radiator as well. This solved my problem, or so I thougt. anyways, a few weeks later, the same thing happened to my mom while she was driving my car to work. So I took a look at the coolant levels and they were low, if not empty, once again.
I haven't noticed any leaks under the car, so I'm not positive there is a leak, and if there is, I have no idea where its leaking from. Any ideas?

Also, after I filled up the radiator and did the oil change today, I heard a bubbling sound coming from somewhere near the dashboard, closer to the passenger side as i accelerated. I didnt hear it anymore, after the engine warmed up. What could it be? Is this related to my low coolant levels, and what must I do to fix it?

Last thing, I also noticed my car idles a little low in park (not sure if it also does while stopped in drive) around 700 rpm. Is this a serious problem? The exhaust pipe seems to make a sputtering noise, not too severe, just a bit, so i dont know if its normal or not, or if its even related to tje low idli g.
Thanks in advance for your respones, hope to hear from someone soon so i can deal with these issues.

 

my first guess is a pinhole leak in the coolant system. Not necessarily big enough to leave a puddle, but big enough to leak under pressure.
Bubbling is from improper bleeding. This is my second guess, as it might explain why it overheated the second time.

There's a few reasons the engine might be sputtering at idle: needs tuneup, failed injector, or dirty injector.

 

coolant...
Why are you over heating?
Are the fans working?
clog in the radiator?
T-stat stuck/clogged?
Does the coolant look clean?
The overflow tank is really not a good indication of what's in your radiator.
when you overheat coolant boil out of the system...air gets in the system and your coolant level drops. address the over heating issue before you try and figure out what's going on with the coolant. if there's no leak and you're not steam cleaning your rear bumper then you're losing it from over heating.
BTW...when the needle is close to H...you want to stop driving...not drive until the car boils over.

noise behind dash...
that's the coolant flowing through the heater core. top off your coolant...bleed the air and the noise will go away.

idle...
how dirty is that throttle body? how about the IACV? plugged up a little?
clean up some of the carbon in there and it might improve idle speed. also a full tune up wouldn't hurt either.

 

I think 700rpm should be fine. I think idle speed is 700 +/- 50.
Coolant leak is hard to see under the car because it evaporates as it touches a hot surface. Try to drain a little bit of your oil and see if it is just oil in the lube system.

 

even if it evaporates it will leave a green residue that you can see if you look around for it.