'90 2600i runs hot

[pops]

Hey Guys, New to Mazdas here. Helped a buddy with his new old truck. runs fine but temp guage stays about 3/4 up when running. We changed all his hoses, new water pump, 180 deg thermostat (195 Deg came out), flushed system and filled with fresh 50/50. Has a 2 row radiator that looks really good just by looking at it, looks almost new inside. Thing will idle in the driveway all day with the AC running and guage sits steady about 1/4 up from bottom of guage. When he drives it, it jumps up to about 3/4 even with AC off and heater on high. Hasn't got any hooter than that yet but it doesn't seem right. I heard talk about air in cooloing sytem? Anything I'm overlooking? Any ideas where to next?

[Tyranitar]

Ok, first off, you need to run the 195 thermostat. Running a 180 degree thermostat keeps the truck in warmup mode, which makes it run very rich.

Second off, sounds to me like there might be a plugged condenser or radiator, not talking about inside, I'm referring to being plugged with bugs, leaves, etc. If you don't get airflow through the radiator, it will not cool properly.

If you don't run the right thermostat, it can trap air, I learned that the hard way, went through a lot of aftermarket thermostats. What you need is the Stant #45869. A lot of other brands lack the jiggle valve and fail to open properly at the rated temperature under pressure.

I would also look at replacing your temperature sender with an ACDELCO Part # F1864. You could try other brands too, most should work fine. Still you get what you pay for. I would suspect that the temp sending unit is reporting a false temperature reading.