Is the thermostat a plug and play type of repair or is there a procedure for bleeding the cooling system when replacing?

 

well for maximas the thermostat comes with the housing--the neck--well every time I have done it they come with the neck--and usually we just refill and make sure there are no air bubbles in the system. you can also use a funnelt that hooks up to the radiator and raise the front of the car up about 45 degrees and run the vehicle for about 10-20 mins. thats how I do it--you'll know if theres an air bubble cuz the car will over heat pretty fast

 

keep in mind that there are two thermostats for the maxima

 

I purchased one from autozone but there was no mention of another thermaostat. The one I have is on the belt side that flows to the lower radiator hose. Is the other one on top of the motor on the upper hose? That looks like a bear to get to.

 

Plese explain further...

 

I am installing the one I have now. I couldn't find info on another thermostat.

 

There are actually two thermostatic devices in the VQ30 engine cooling system. The main T-stat is as descibed in the above posts. The second is called a "water control valve" in the service manual and it controls coolant flow around the cylinder walls. All coolant passes through the main T-stat which opens at 180 deg F and starts coolant flow around the heads. The "water control valve" opens at 203 deg F and adds the cylinder block to the cooling loop. It is physically located at the rear of the engine, below and to the left of the throttle body. Its housing has a small bleeder bolt on top. The "valve" itself looks like a high quality stainless- steel thermostat and costs about double what the main t-stat goes for.

 

I changed the thermostat and I am still having the original problem. It may well be the water control valve that allenmason was mentioning. At idle the gauge stays at the normal level. Around town the same. When I get to a highway or uphill that is when the temp starts to rise towards the H. I tried to do a search for the water control valve but no luck. Maybe it only available through the dealer????

 

Interesting! I never knew this.

 

I am also having a problem with my air cond. According to my gauge there is freon in the system. It just keeps cycling on and off. Can these problems be related ?

 

Anybody know if the 3.5 also has two? Just curious.

 

Its probably not the water control valve as the coolant temp sensor takes its reading near the main thermostat that was just replaced. The symptoms suggest a coolant flow problem with possible causes being a plugged radiator, collapsing hoses, or "air" in the cooling system. Here is a quick air check/bleed proceedure--With a COLD engine, check the coolant level at the radiator cap. The coolant level should be at the top of the filler neck. If you have not done so since the T-stat replacement, loosen the small bleeder bolt on top of the water valve housing and retighten (gently) when you see coolant being expelled. Top off the coolant, replace the radiator cap & drive. If it overheats again, let the engine cool and re-check the coolant level at the radiator cap again. If the coolant is again "low", you probably have a real problem with a head gasket or a cracked head that is allowing exhaust gases to enter the cooling system. If the coolant level is good, start looking at the radiator and hoses.
The 5th Gen Max is not prone to head/ head gasket problems unless its been seriously overheated--as would any car.

A/C compressor cycling could be normal or a symtom of low R-134a refridgerant depending on the ambient/cabin temperatures and refridgerant pressures.

 

Thanks for the info. In regards to flow problems can a water pump be suspect?

 

I doubt the water pump would cause a low coolant flow problem in the Max-- the seals would normally give out and leak long before the W/P impeller would wear enough to reduce coolant flow--and that would be at very high mileage using a anti-freeze with a silicate additive typical in U.S. antifreeze products. Nissan and other Japanese automotive antifreeze does not contain silicates.
In your case, if the air bleed procedure does not help, I suggest you have a a shop evaluate the cooling system.