Ok, so my 83 Z28 is all stock (for the most part, no real performance upgrades) Ive owned it for 2 years now and daily drive it in Florida. For those 2 years it's been running super cool all day every day, like in the 120 range. Well yesterday I happened to glance down and saw it up around 220. I did a double take and saw the needle move down to 160 or so, so I figured maybe the thermostat just opened or something. But I had never seen the car go up to 220 the whole time Ive owned it, never.

So this morning I pay closer attention. It goes up from dead cold to 120, stays there for a minute, then climbs up to 220 and keeps going 240, up to about 260, nearly in the red. Then just as it gets close to the red, it comes back down to 150 or so. It stayed at 150ish for about a minute, then went back up to 240 and back down to 150. Up and down, up and down for about 12-15 minutes when it finally went back down to it's normal 120ish spot and stayed rock solid the rest of the ride to work.

So what could be my problem? Bad fan clutch? Bad thermostat? or bad water pump? I dont hear anything coming from the engine bay as far as odd noises.

 

The first thing I'd do is to check for a soft or collapsing hose, that everything is in place (air dam etc), fan blade is tight, belts have proper tension, that there are no leaks, and you have proper fluid levels when cold. Then for the money and effort involved, I'd change the thermostat and radiator cap to see if that resolves the problem.

 

Well, I appreciate the reply. Drove it home yesterday and checked the fluid, it was really low, so i topped it off. Suddenly hear a drip drip drip under the car. Trace the source... front bearing on the water pump. New pump is in and all is well now.

 

Good to hear that you found the problem. It sounded like a low coolant issue. Good luck with it!

 

Hope you didn't crack a head! empty reservoir = bad