When I flushed my coolant (30k miles) I refilled the radiator and then refilled the coolant overflow bottle to mid-way between MAX and MIN. Today, (55k miles) I noticed the level it at the MIN. Now, some of this has happened through air in the system I'm sure. I'm wondering if there are any known problems with the 3.5 and head gaskets? I'm not seeing any white smoke, but it wouldn't take much...the loss was around 1 cup of fluid.

 

My moms car does the same thing. You fill it up between Max-Min and then it eats it up to just above min and stays there.

And I was wondering the same thing with the head gaskets in the 3.5.

 

You've lost 1 cup in 25K? Don't sweat the small stuff! Flush the radiator again in 5K and forget about it.

 

Prob just air bubbles, hopefully atleast haha

 

If you have bled via the air relief valve you should be fine. When I flush and bleed, there is some coolant fetched from the overflow tank. But after a few days drawing coolant from the tand will stop.

Now, Nissan's are tough to bleed and always certainly have air pockets in the system. I wouldn't get too worried if the drawing hasn't stopped just after a flush, but if you are loosing 1/2 Q or so then you need to do a pressure check for leaks, and possibly for coolant in oil by sending a sample for analysis.

White smoke from the exhaust is a good indication that you have an impending head gasket failure (which incidently is remote).