C4 Cooling System Problem

[DannyC4]

Okay, I have an 84 Vette. The previous owner had installed, what I think its called "Prestone Fill N Flush T" on the heater hose, and everything else was stock on the cooling system, it was working okay. And then, I installed the low temp fan switch, and it was working ok, a little bit cooler than usual. (I dont know if this is what caused the problem or not). I ran good for like about 2 months, untill last nite, the "Prestone T" (which is made out of PVC or some plastic) broke while I was driving back home from work, lots of steam coming from under the hood, it scared the shit out of me, I thought it was smoke at first. So, yeah, the coolant got pretty hot, the gauge was getting readings of above 265, but I made it home. I got a new heater hose, and installed it this afternoon, I fired the car up to start refilling the coolant, and I noticed the radiator got full, and the coolant temp gauge was climbing up pretty fast, and then the fan kicked on, as it should, everything looked okay at first, but again, the coolant gauge was way up, around 260-270 or so, I shut the car off real quick. I also noticed that the coolant in the radiator was cool, I thouched the upper radiator hose and it was cool too, but the heater hose was hot. It sounds to me like the T-stat got stuck in the closed position, maybe because of the very high temps or the lack of coolant or maybe both. Or could it be the water pump? Is there a way I can test them? I already have a 160 deegree T-stat ready to install tomorrow afternoon. But I really would like to know how to test the water pump and the T-stat before I take it apart. Thank you very much everybody.

[DannyC4]

Alright, I installed the new T-stat, and everything seemed to be working fine, I totally refilled the cooling system, everything was fine, the T-stat opened and the water stated flowing, but now the cooling fan doesnt want to kick on, I installed a low temp fan switch around 2 months ago. How do I test the relay? or the motor? Has anybody installed a manual fan switch? How hard was it? Thank you everybody, Im struggling here, and trying my best to get it going myself. Happy Hollidays!

[DannyC4]

Cool, I think I got it fixed. It was the relay for the cooling fan. Did u guys know that if you use the fuel pump relay the fan will run regardless of the coolant temp? Its like if it was bypassing the fan switch, I found that out by accident. Im gonna keep that relay in my car as a back up, just in case if I need my car to run cooler. The only bad thing is that the fan still will be running even if u shut the car off, you have to open the hood and unplug it, but yeah, cool trick if u wanna keep ur fan running all the time and dont want to put a manual switch. Later Guys

[DannyC4]

Awesome, I just finished installing the manual switch for the radiator cooling fan, and man, it works great. That switch and the 160F T-stat is what I needed. I live in Tucson, AZ, and it gets really hot during the summer time, that was just what I needed. My vette never ran so cool, I am very pleased with the results. I mounted the switch under the dash, so you cant even tell its there. Thank you guys for your help and support.

[TEXAS-HOTROD]

On hot days w/the a.c. on, mine would run 220+ while driving in down town traffic. I have a 160 t.stat and a 170* fan switch. I came across a factory secondary cooling fan that I installed in front of the ac condensor. It lowered my engine temp by 5 to 10 degrees.
Every little bit helps. Glad you got yours fixed.