new cooling issue
I've had my 68 camaro since last august. It has the four gauge cluster on the console. SBC 400 (late 70s) and a TH350 automatic trans.
The temp gauge had always registered one small notch past the first large notch despite weather or distance driven. I guessed that was an inaccurate reading as it would likely be only about 120*. In Oct, after getting it back from the shop, the gauge started registering different temps. It will show temps raising pretty steadily on idle, but will go up to the yellow line (about 211*?) and then fall back a few notches and go back up to the yellow line while driving.
I was concerned that the t-stat wasn't opening, so I pulled out the pretty old 160* and put in a new (tested) 180*. intake was dry so I think the 160 t-stat had failed. Afterwards, I let the engine idle for about 5 minutes and temps sat at the beginning of the yellow line.
when I took it out for a drive, the temp would go back to the yellow line with acceleration and drop down to about 190* or so when I was idle at a light or off the accelerator. Air temp. was about 70*.
When I checked radiator coolant, it was low, so I added 50/50 coolant about a week ago. Yesterday, the coolant looked about 4 inches lower than my previous fill line (checked on cold engine). I think I'd only driven about 2-3 very short trips in that time. Radiator is unknown age, but a stock type with stamped reservoirs. I have not seen any puking out the overflow. The rad. cap is an unknown lbs rating. Am I checking this wrong? The level of coolant shouldn't change that much should it?
I have checked the temps in the engine bay with a laser a few times. block in front and on side by temp sender were at about 210*, top radiator hose was about 193*. Lower hose was around 160* something. It appears that the temp. gauge is reading pretty close.
Am I getting normal operating temps? Seeing the temp needle go in to the yellow part of the gauge is concerning.