Need expert help, 01 pathfinder overheating!!!!

[ZMQguy]

01 pathfinder, no heat, overheating. This has been happening randomly for about 6 months. New radiator and thermostat 6 months ago didn't solve anything. Suspect air lock or rear thermostat. Last night I tried airlifting it. Worked fine in the shop. Left the shop and after 5 minutes in -3 degrees had no heat again, 5 minutes later it overheated. A rural road when it's 3 below zero is a pretty crappy place to be stuck on the side of the road.

[EdBwoy]

No expert here, but I don't shy away from challenges.

Here are a few questions that pop to me to start off:
1. Are you losing any coolant? It might be from anywhere really, which includes clamps with crusty coolant between the rubber and metal tubes
2. Is your radiator cap in good condition? I like OEM for this
3. Have you tried using the coolant bleeder at the firewall? It's pretty effective in my experience

*And oh, when it comes to thermostats, a lot of people on other platforms have had problems using anything rather than OEM Nissan

[ZMQguy]

No, I don't believe it's losing coolant. Its hard to tell honestly. It loses much coolant when it boils over. Tried the rear bleeder. Cap and thermostat are new. Neither are OEM. Was almost wondering if it isn't a head gasket. Its near 200k and also consumes 2+ qts of oil every month.

[EdBwoy]

Well, for the head gasket, the sweet-smelling white smoke should also accompany it.
For oil consumption, 2 quarts per month is a little too much... well, depending on how many miles are covered in a typical month. Have you replaced the PCV valves recently? The changes can be dramatic.

I'll try to look at the cooling system layout to see what kind of issues a failed rear thermostat (water control valve, they call it?) would cause.
What would it take to address it though, extra intake gaskets as you take the intake apart for access + a chance to look at the power valve screws?

[ZMQguy]

I haven't looked into it too much. I did a while back and seem to recall it's quite the job. If I undergo it I'll check the power valve screws but, if they haven't come loose in 200k.... or maybe one did...what issues would that cause?

[atro]

most likely air in the system , or a bad thermostat. go with oem thermostat and radiator cap and bleed the air out of the system. also go with an oem fan clutch as aftermarket are horrible.

[skipfletcher]

I went through the same thing with my 2001. It was head gaskets. Check your oil cap - is there a yellowy foam? Also, a combustion gas leak test kit will confirm.