I have 00 Maxima with 212,000 miles. For about the last 15,000 miles the coolant leaks from the radiator into the reservoir almost filling it to the top. I can see gas bubbles going into the reservoir. Some of it then goes back into the radiator but there is still too much in the reservoir. After it cools, I pick up the reservoir box and let the coolant go back into the radiator, but he same thing happens again the next time I drive. The radiator and the cap where replaced about a year ago. Other than this problem the car runs perfect. Does not over heat, make any weird sounds, and there is no smells or smoke coming out of the exhaust.
What could be causing this? Could it be the water pump, or is it the head gasket?

 

Most likely a head gasket.

 

I bet it is a partially clogged radiator.

Test it out, drain the radiator using the drain plastic bolt, it should drain real fast and then trickle slowly towards the end. If the drain is slow, you are having a partially clogged radiator.

 

Sounds like a broken head gasket.

 

change both head gaskets. also send the heads out to check for warpage.

 

Bubbles make it sound like a head gasket.

Have you seen other symptoms? White smoke collant in the oil? Running hot (when the rad is full)??

Before you jump to any drastic conclusions change the radiator cap. They are made to pressurize the system to a certain PSI. If that fails, I can't remember which way (either letting the pressure get too high or spring is too weak anmd the PSI is too low) the system may let the coolant push past the cap into the reservoir. A couple dollar cap is way better than a head gasket replacement.

Cross your fingers..

Good Luck

 

If the coolant gets too hot and starts boiling, it will also run over into the reservoir. Have you checked coolant level (not in the reservoir, but actual level in the radiator)?

Head gasket on a VQ30 is unlikely even under some dire circumstances. Before condemning that obviously you'd want to do compression and leakdown tests.

 

I'm having the same prob wit my 02 mazda 626 , i replaced the radiator cap and no change, i dont think its a head gasket tho cuz its not bubbling under the cap when its running.... idk wat to do lol

 

Steal someones nismo radiator cap and test it out. If it still boils over secretly put their radiator cap back on their car and check radiator.

But forreal doh. If your radiators clogged, that means theres debris in the coolant passages and you do t want that in your passages. If radiator cap dont work, try a mini flush first. If that works out do the rest of the coolant flush.

 

I just realized this is an old thread.

 

my radiator was clogged, i knew it wasnt a head gasket cuz i took of the rad cap while my car wuz running and there was no bubbles and it cant be the water pump cuz it would run hot, but i took my radiator off and ran water through it from the hoes in the top and bottom, you shoulda seen the stuff in it lol now its not putting the coolant in the res. when i shut if off
thanks to whoever suggested the radiator