Possible air in system??

[Petergunn]

I have a 1999 QX4 3300 v6. I can drive all around town all day without the A/C on.... no issues. I can turn the A/C on within just a few miles I notice the temp gauge starting to climb a bit. I never let it get over 3/4 of the way up. I can change to heat, vents and recir and the temp starts to drop back down. There is ample room between the rad and a/c coils to see that there is no trash or blockage. I can shine a light through either one and see the light very well. I recently got this and not 100% on whats been done. The coolant is clean and green, water pump "looks" new and thermostat housing looks clean and replaced. I did replace the fan clutch just to be on the safe side. I also replaced one hose that was crimped ( someone used straight hose instead of molded). I followed the instructions on removing air from the system ( Car on ramps... jug in rad.. open vent screw..ect ect ect..) It only has 146,000 on it. Any suggestions?

[Slumpert]

Most likely the PO had the exact same thing going on and decided to sell.

Maybe try to backflow the rad and see if you can get some gunk out and make sure it is not clogged with sealers and other crap the PO might have done. Be sure to disconnect both hoses. You dont want to push anything into the heater core.

[Petergunn]

I'll give the back flush a try in the next couple days, depending on the weather here. I didn't really think it was radiator related since it only did this when the a/c was on and putting more drag on the engine, but an easy enough trial and one way to eliminate one more thing.

[Towncivilian]

Also inspect the radiator cap according to this TSB.

[Petergunn]

OK.. heres whats been done thus far....
I haven't replaced the water pump or thermostat due to the "looks" of the ones on it.
I have replaced one hose due to the old one being kinked. Never had any issues before I did this, that's why I think there's still air in the system.
New fan clutch
Flushed radiator, although all was clean and green
New radiator cap
I followed instructions for bleeding air from the system
I can shine a light through the radiator and a/c coils and nothing seems to be blocking the light.
I have had issues with air in cooling systems before and this is what this seems to be, I drove it today after the flush and bleeding. Without the a/c on it seems to be fine. Just when I run the a/c is when it tends to go up above the half way mark. The overflow tank has taken a bit into the radiator after the first drive, I topped it back off to the mark.

[Leo1998]

I don't know if this helps...I had the intake off my '98 Pathfinder VG33E a couple days ago and noticed on the bottom there is a tiny coolant hose and on mine it was kinked really bad, I was surprised my temp didn't go up but I don't use the A/C. I was wondering how it could have gotten kinked so bad and it must of been when I took the intake off 3 months ago to do the valve covers. So if you are checking every possibility, there's that.

I did fix mine, had to replace with a shorter new hose.

[Petergunn]

That sounds like the same hose I just replaced, but I'll double check a few hoses.. Thanks for the input!!

[Leo1998]

There are two more small coolant hoses coming off the back of the intake, maybe air trapped in one or both of those short hoses. I just replaced both on mine and i found it easier to get rid of the squeeze clamps and use the old school clamps with the flat head screw tightener.

[GX470]

How old is your radiator? Even though it might look clean from outside and have clean coolant inside, it would still be clogged up somehow. I had a very similar issue like yours (posted on the other thread) and it was solved by replacing with brand new radiator and cap.