Ok- My coolant temp problem still exists. I've had the themostat replaced, coolant flushed and replaced. I do not believe it is an air pocket issue. I'm wondering whether it might be the water control valve, water pump or both. I seem to be running at normal temp for the first 15 min, then temp rises. Highway driving (above 75mph) causes the rise to occur sooner. Running the air condit also seems to cause the rise sooner. Conversely, running the heater full blast can drop the temp some. Hoses appear ok. Help

 

Coolant air pocket is the typical, and known to be very problematic. Without proper airbleed procedure, it surely is an issue.

Also blocked rad or rarely cylinder wall/head 'sediment incrustation' (or maybe its called boiler sediment), reduces coolin capacity. Radiator may be rotten/blocked inside, or airflow reduced because of killed insects.

Yes, Cabin Heater works as a liquid cooler...

 

So you don't think its the water control valve or the pump? If I had the system power flushed and replaced, are you suggesting I might still have an air pocket problem? If it is, I'd like to go back back to where the system was flushed and have them try and correct the problem, but how can I rule out the other issues. Is there a way I can determine if the radiator is restricted? If it was, would the temp not rise to high immediately (instead of this delayed rise I experience)? Could the pump have broken or worn fins which cause the temp to rise at high speed? I'm about to give up and go to the Nissan dealer for my raping, so if you have any other thoughts, I'd appreciate them.

Thanks

 

Earlier suggestion for corroded pump blades is still a possibility. Why it happens, dunno. Bad acidic coolant (!?) is one cause if used (tap?) water is non neutral pH7... They say distilled water would be best.

The service manual has a process for air bleed which has to be done after any coolant service fillup, check mentioned links... (The car front is to be raised and engine run hot while bleeding screw is ajar.) If its not followed, air pockets will definitely cause problems. Is it your -and- only cause, cannot know. Bleeding is cheap and easy process, needs to be done each time when coolant has been out.

- Radiator airflow, visual inspection; very seldom blocked.
- Radiator coolant flow check needs taking tubes out and letting water through.

- who knows if your new thermostat is working? Would not be the first dead tstat... check that it opens in boiling water kettle.

Any of the discussed causes (except air pockets) happens really very seldom, so I'd concentrate on the bleeding as its the most common maxima 'problem' after fillup. This is 'problematic' because maximas coolant tubing is much more complicated than 'average' vehicles visiting workshops and need special care in this process. Most service ppl can barely read, so gettin this issue hammered in might be impossible...

If the air pockest form in the heads, they cause hot spots which may destroy/warp heads, so correct the problem now before drivin long/hot.

Edit: The mentioned valve controls coolant flow to cabin heater. It is a peripheral system only for passenger convenience... Its status has absolutely 'no effect' on engine and its cooling. Check out the coolant flow on VGE from http://www.cardomain.com/ride/748507/7 and http://www.cardomain.com/ride/748507/8 ...its mostly the same as on later models.

 

The continuing saga. It is now with the Nissan dealer (for 5 days now). They thought it also was airpockets and were convinced they solved the problem...till they drove it about 20 miles. Once again the temp rise. Theyhave consultedNissan TechSupport.- They are now checking to see if the wrong theromostat was put it at last service (or if thermo or temp control valve are in correctly). This is a stumper....seems even for Nissan

 

If smtg is loose, like ripped hose part, it may intermittently block flow... possibly input/vacuum side hose collapse after warmup, triggered by certain vacuum/temp -level?

 

Nissan dealer now convinced it is radiator.......$763! But they guarantee 100% the problem will be solved. [We shall see]

 

Thats how stealership nickname is earned: Youll get new&good radiator for "200$" from the next spare shop... they may try but cant force you to buy one with such ridiculous price.