I took the vette for a 2 hr drive the other day and was cruising at about 65-70 mph in 40 deg weather. No traffic, cool day, etc. The temp gauge would sit about 180* for 3-4 min, then slowly creep up to around 205*, stay there for a few min then come back down to about 180*. The cycle was pretty consistent. I have a ZZ454 with a Dewitts radiator and dual spals. I know one of the spals is not working right now (been too lazy to troubleshoot that one), but the other comes right on with the 195* switch. However, with as cool as the weather was and the fact I was keeping a constant 2500 RPM or so, the temp should be rock solid at 180ish, right? Shouldn't the coolant/radiator be enough to keep the temp consistent when cruising without even using the fans...especially in cool weather? Honestly I'd be afraid to drive the thing right now if it was summer. The temp sensor is also brand new, so I believe the readings, just not sure why I have this weird 20* fluctuation...especially when the driving condition and RPMs remain exactly the same throughout the "cycle."

 

I'm guessing ,180 thermostat ? You have a 15 degree difference between thermostat and Spal switch. IMO sounds about right for low outside temp.

 

I agree with Roger, not sure you have a problem. Get the other fan working and I think you are good to go in hot weather.

 

Or, reset the temp sensor on the fans to match the thermostat. Roger is "on the money" with his assessment.

 

I do have a 180* thermostat. Never even thought about the 15* difference thing. Am I OK sticking with this setup (obviously getting the other fan working), or is it advisable to lower the fan switch to 180*?

 

If you are OK with running at 195F, leave it alone. The original small block V8 was intended to run at 180F for best durability, mileage, and performance (or rather, combination of all three). The 195F temp was stipulated by the EPA to help burn off more hydrocarbons with elevated temps. Non-computerized engines will run perfectly well at 180F [maybe better and longer], but some computers/sensors expect to see more than 180F to 'know' that the engine is up to normal temps.

 

It seems to me running at 180* consistently would be better. I don't have any computers, sensors, etc. that care about temp, so all I want is performance, durability and longevity from the engine. I'm assuming to do this I need a 180* temp sensor. I have dual spals from Dewitts, but his website does not sell anything other than the 195* sensor. Any idea where to get a 180*?

 

Mike
180 is the opening temp. You don't turn the fans on at 180.
Do you have the all rad. seals in place & the little factory lip
"spoiler" or some other front spoiler?

 

I have all new seals in place as well as the spoiler. With the old 350 engine in the car, it ran steady at 180 no matter what. With the new setup (ZZ454) it does as I described above. It just seems like the temp shouldn't wander around so much. I can understand 180-190 fluctuation, but it seems like 180-205 is too big of a range, especially when just cruising in cool weather and not getting on the gas or anything. Is the SB-BB difference just b/c I have electric fans and not a mechanical fan (like I did w/ the 350)?

 

Yes "too big of range" for
Check lower rad. hose for spring/collapsing.
Sounds like air or water flow problem. Assume full, no more than 50/50 antifreeze.
If no problems found, change or test thermostat.