i know you guys have seen this a 1000 times but my 97 z28 vert 6 spd runs too cool when driving and slowly overheats at idle.i have bled system replaced thermostat and sensor in head and sensor in water pump.if i start it and drive it ,it never shows more than a quarter way up gauge and if you let it idle it slowly over heats(of course it has never hit red zone)im more conscerned about not showing that it ever gets warm enough while driving.but if you open hood the radiator hoses are warm.this is my first z28 and im not familiar with the cooling system on it.it has a 180 thermostat.thanks in advance for any help,i have been reading this forum for a few weeks and you have some very good car guys.

 

Sounds like the fans are not coming on, could be the relays under the hood, or the fans are worn out. The engine temp when driving sounds good, a little above 1/4 is normal.

 

dont know if the 97 has two coolant temp sensors or not. mine has two. one for the gage and one for the computer. test the one for the gage and see if its giving good numbers. unplug and sick a ohm meter on it.
ECT Temperature vs. Resistance Values

∫C ∫F Ohms
100 212 177
90 194 241
80 176 332
70 158 467
60 140 667
50 122 973
45 113 1188
40 104 1459
35 95 1802
30 86 2238
25 77 2796
20 68 3520
15 59 4450
10 50 5670
5 41 7280
0 32 9420
-5 23 12300
-10 14 16180
-15 5 21450
-20 -4 28680
-30 -22 52700
-40 -40 100700

 

mine does this, i had it over to chevy to see if my fans come on, i was told that the comp wont kick the fans on (i forgot exact temp) but is really close to the red zone, (emissions) so i wired in a manual fan switch so if im in the drive through or sumtin i can hit the switch when the temp starts to rise

 

it runs under 1/4 when driving and then it climbs when idling i just put a new water pump in today and new rad cap and i replaced thermostat and both sensors last week

 

do you have yours on all the time or just when you need it?
i also have a manual switch.

 

should come on at 220 unless u have the computer tuned then u can have them come on sooner. yah should get up to the third mark or close to it then come on. im using a 180 thermo and it says at 180 unless the transmission is getting hot then it goes up to 200 or so.

 

just when i need it, i only need it if its over 65 outside and if im idling for more than like 4 mins

 

Where did you get your manual switch from? Or how did you make it? I'm having this same problem.

 

http://shbox.com/1/fan_sw_diagram2.jpg