Not quite overheating

[chaseincats]

Hey gang, got an odd one for you.

My car used to sit rock solid at 170 (has a 170 degree thermostat) but within the past year that's become more variable depending on if I'm sitting idle or driving.  If sitting idle in 95 degree weather, it will go a little past half which I know isn't bad but the fact that it used to sit rock-solid at 170 regardless of weather tells me there's something wrong and even though its not severe it's annoying lol.

I've changed the fan clutch, thermostat, water pump, checked fanbelt tightness, changed coolant, used a flushing chemical, and even got a brand new radiator but while the temperature isn't moving as much, the needle still moves depending on if idling or driving.  There is definitely rust in the system because the PO used tap water and ever since I got it years ago, its been a game of 'how much rust will come out with this flush' (its always less but there nevertheless).

I've also cleaned the temp gauge harness connector/sensor outlet and nothing has changed.  I'd have thought it was the temp gauge if the car didn't go back to 170 like it used to while driving - but since it does, it tells me the temp gauge hasn't lost calibration and the coolant temperature really is changing.

Any ideas?

[siteunseen]

I've had to use an air compressor to clean my radiator in the beginning of grass cutting season down here. The lazy guys blow the mess into the streets and it gets in my air filter and radiator 

[chaseincats]

7 minutes ago, siteunseen said:

I've had to use an air compressor to clean my radiator in the beginning of grass cutting season down here. The lazy guys blow the mess into the streets and it gets in my air filter and radiator 

I'd give that a shot but I got a new radiator and took it for its maiden voyage last Thursday when I noticed the car still had the issue

[siteunseen]

New info. You may have some kind of air in the system if it started with the new rad?

I'd let it run, idling, until you see flow under the cap. Rev it up pretty high and let it burp. Then top it off.

Goodluck!

[chaseincats]

4 hours ago, siteunseen said:

New info. You may have some kind of air in the system if it started with the new rad?

I'd let it run, idling, until you see flow under the cap. Rev it up pretty high and let it burp. Then top it off.

Goodluck!

Unfortunately the problem with the old rad/thermostat/water pump/fan clutch persists with the new rad/thermostat/water pump/fan clutch even after burping it.

[jonbill]

did you check the new thermostat before installing it? new ones can be bad. 

Also, is the valve central in the thermostat or offset to one side? if offset, I think its possible to install it so it can't open fully. (one side of the thermostat housing is shallower) 

[chaseincats]

8 hours ago, jonbill said:

did you check the new thermostat before installing it? new ones can be bad. 

Also, is the valve central in the thermostat or offset to one side? if offset, I think its possible to install it so it can't open fully. (one side of the thermostat housing is shallower) 

This was an aftermarket thermostat with an off-set valve.  I'd definitely agree that could be the case but the thermostat I had in there previously was only a couple years old and a genuine nissan part with a centralized valve but after changing to this thermostat the issue didn't change.

[SteveJ]

Has your fuel pressure decreased causing a lean condition?

Lean=hot

[chaseincats]

I have an air/fuel gauge on here and it sits at 13.8 at idle which is pretty standard.  Cruise is 14.2-14.7 depending on speed and WOT is around 11ish.

[jonathanrussell]

might do a compression test. could have a slight head gasket blow / leak. losing any antifreeze? Oil look normal?

[chaseincats]

Oil looks good - it's always thrown a small puff of white coolant smoke on a hard acceleration gear change though

[jonathanrussell]

hmm. that could be your clue. eventually that will worsen over time and affect temp. Maybe it worsened a bit when you noticed the change in temp. Will also corrode your cylinders (and clean your piston tops)  if the car sits for any amount of time. 

If you think you have a blown head gasket....I would encourage you to pull the head and fix it.

J