Help on Temperature Issue Please!

[808countryside]

I have a 1985 Nissan NapZ 720 king cab and I live on the island of Oahu. The problem I'm having with my truck is when I'm stuck in traffic ( just getting off of work) my temperature gauge goes up about halfway, but once my truck is on the move the temperature gauge drops to about a quarter... never got to the point were the temperature rises beyond half (never got stuck in traffic long enough to see if it would go higher)... Is this normal? or is there something that could be wrong? I was thinking it could be the Coolant Temp. sending unit? CAN ANYONE HELP W/ THIS PROBLEM OR HAVE FIXED THIS ISSUE THAT I'M HAVING!!!

Mahalos,

[Aven]

Could be your thermostat, or it could be your fan belt slipping or it could be your sending unit. Might not be a bad idea to flush the system and change the thermostat while its empty.

[PEZi]

yeah... its not really a big deal if its not getting over half... however, the fact it goes up that high compared to when you're driving might suggest it's time to flush the system, check belts and possibly see if the water pump is working properly

[86 720]

Fan clutch needs to be replaced OR the radiator needs to be cleaned inside & out...

While driving, the frontal wind is blowing over the radiator fins cooling the coolant. While stopped, the fan clutch is supposed to blow wind over the radiator fins to cool the coolant.


Since the fan clutch and water pump are one unit, you will have both a new pump and clutch! Get the cast iron impeller pump, not the metal fins. Might as well replace the thermostat and coolant while you're at it.

See my post for directions:
my-720-build-page-t489230.html

[808countryside]

Already changed the radiator and has new coolant... I haven't changed the thermostat yet... it seems that the water pump is still good because when i look into the radiator, i could see the coolant flowing . i think if the thermostat was bad the truck would over heat very quickly while in traffic?

[86 720]

My guess is still the water pump/fan clutch. You can try the thermostat, and it might be it, but if it still is overheating than it would be the fan/pump. Much cheaper to try the thermostat first.

[Charlie69]

Check your timing advanced or retarded both can cause higher temps. If timming is good maybe fan clutch. Did you have the block flushed before changing the radiator. Might be a restriction of build up in the block.

[flinterman2000]

What He (Charlie) said.

[mattthruwalkin]

hello i am a new guy , but my 84 720 4x4 does the same thing as yours , look at the fan blades closely . do the tips look like there broken and is your fan shroud busted in any way?

my fan looks like its hit the shroud where the previous owner forgot to tighten up the bolts in the lower part of the shroud this busted up the tips of the fan blades and made them shorter so now i get less air flow and run warmer at long stop lights or traffic jams , also if your not running the truck with antifreeze in it ? if not add some this mite lower the running temp some

[synack7350]

glycol (anti-freeze) is actually a worse thermal conductor than water. Adding it would actually raise the running temperature as it is not as efficient as straight water. We only use it because it raises the boiling point and lowers the freezing point of the liquid over straight water. Just thought I'd drop some science on ya.

[synack7350]

oh and a slow creep in temperature, at stand still prolly isn't something to go spending a million bucks on. Its just indicative of reduced flow over your radiator, or radiator has lost efficiency due to dirt, oxidation, bent fins, whatever. Flow reduction either by obstruction (in block or thermostat not opening fully, slipping or damaged pump impeller, slipping belt or pully. Fan not turning to speed, fan shroud missing) Are all potential root causes as well. I'd start at the very cheapest and work my way up if it were really troubling me.

[mattthruwalkin]

and pure water = rust in the system i run only water due to minor leaks and rather not keep spending money on anti freeze
and i have pure orange rust water

[PEZi]

I run straight water plus an additive for cooler temps and corrosion prevention.