So I've been having this problem for a little bit now. It seems that my coolant likes to bubble out of the water cap on the filler neck. I switched the one on the filler neck with the one off of the AST and that seemed to fix it for a little bit. Then I noticed that the water was now coming out of the AST, so I bought a new cap for the AST so I'm running 16 psi caps on both. Now its coming out of the filler again. I'm not getting any white smoke on start up and I'm not over heating. What could this be? Clogged watter passage? Water pump issues???

 

The cap on the filler neck is not a pressure cap. Try new, and correct caps, but that may not be your problem. If you get a lot of bubbles/pressure, it maybe compression blowby leaking out of your water seals. Symptoms include the oveflow tank overflowing and constantly having to add water (from water leaking into the engine) which produces the othere tell tale symptom, white smoke

 

No bubbling from the overflow res, no white smoke, and the only reason it seems I need to refill the water is because it's leaking out of the fill cap. I can see it leaking out when the car is warmed up.

 

Try new, and, correct, caps then. Is your AST stock? Some aftermarket ones supposedly had fitment issues at the cap

 

Get a pressure tester with cap accessory and test your caps until you find one that cracks at 13 psi and holds pressure for at least an hour. You'd be surprised how many NEW caps on the market do NOT hold pressure.

 

The filler neck cap is just a seal and does not release pressure. You can use a pressure cap on the filler neck but if it is leaking it is because of a sealing issue between the cap and the filler neck. Check the sealing rubber and check the neck of the filler for damage.
I have been using pressure caps on both the filler neck and AST for years without any problem so as long as the seals don't dry out and get cracks.

 

The filler neck cap was the one that was leaking originally. I switched the cap the AST to the filler neck and it stopped leaking, or so I thought. I then noticed it was leaking out of the AST but the filler neck was fine, so I bought an other 16 psi cap for the AST. Now it's leaking from the filler cap again. I get no bubbling from the overflow but when I turn on my heater/defroster I get a nice aroma of coolant in the cabin. Don't know if because the problem has something to do with the heater core or if its just because there's coolant under the hood,

 

Actually now I get a strong smell of coolant randomly weather the defroster is running or not. I tried switching to recirculating and I still get the oder.

 

is you carpet wet?

 

Just took a short drive and carpet seems dry. I even turned on the defroster on full for a little to see if that made a difference. All it did was make my cabin smell like coolant.

 

Sounds like you may have several issues. Pressure test your system. If it doesn't hold pressure you know you have a leak somewhere. If you're lucky, you will see it. If your hoses are original, it may be best to just go ahead and replace them all

 

And to troubleshoot the heater core, try pressure testing with the core bypassed. If it holds bypassed, but not, it's your core