So I have a 2003 6 speed which I will be doing some serious maintenance to over the next several months because it needs it.

Question #1: I know for sure that there is probably going to be an oil leak on the rear valve cover. I think I read on several threads (suck at searching on this site) that you can use a valve cover from a 6th gen because it is made better. Is this true and which year?

Question #2: My car warms up extremely fast, even in the 10 degree weather (within a few minutes it shows up to temp). Then I turn the heat on and start to smell coolant and the car even starts to overheat if I am driving at highway speeds or a bit fast. Coolant begins to boil out of the overflow tank (have witnessed it after stopping and opening hood). I am not good at all with diagnosing problems on the coolant system.

To me it could be several things... Over the summer I flushed the coolant, did NOT use pre-mix and used distilled water and coolant. I also changed the thermostat and radiator cap. Now I am thinking maybe the coolant mixture is ****, the thermostat is defective, the water pump may have rotted blades, my heater core may have taken a **** or the worse case scenario head gasket is blown (I do not have white smoke out the exhaust nor do I smell coolant burning from my exhaust and my oil is not milky).

Any help with this would be greatly appreciated.

 

I swapped my rear valve cover back in the summer when the plugs were changed and the NWP spacers were install, so to answer the first question YES you can swap in the 04 (6th gen rear valve cover) and for 1/2 the price of replacing the 03 version. The 03 version tends to develop hair line cracks inside which allow the oil to get into places you don't want it, The 04 version is much improved in construction and takes care of this problem.
Sorry can't help on your second question, as it appears you have several variable in play one being that your coolant mix may be way off along with a host of other potential problems that you have mentioned.

 

First - yes swap them they are built better.

Second - either "burp" your coolant system, or do a flush and fill at a shop. You have air in your lines most likely. Common issue with the Maxima.

IF you never have heat then yeah your heater core could be plugged and will need to be flushed..fairly easy to do.

 

Thank you for the replies... I am hoping that the coolant mixture is totally wrong. Since the weather sucks it will be hard for me to do this now, however I am going to buy some quality coolant, some coolant system flush and do this over again.

I am definitely going to buy the 04 valve covers, spark plugs, and Intake Manifold spacer kit. Will keep you guys updated.

 

the only way the coolant mixture could be wrong is not enough antifreeze and it freezes solid. so keep lookin

 

How would it possibly freeze if the car warms up really fast and is almost like the mixture is boiling? I am going to start with a complete change of the fluid and use OEM Nissan fluid.

 

That's the only way a coolant fluid issue would manifest itself, is what he means.

Sounds like a stuck 'stat.