I took my car out of storage (I drove it occasionally while it was in there) and within 2 days, while i was in idle traffic in a busy shopping center and drive thru, the gauge hit the red shaded area and started dinging.

I pull over and check under the hood, the surge tank with coolant is nearly empty. I refilled it like the manual suggested, i had to fill it up twice actually as it predicted. From the manual:

"With the coolant surge tank pressure cap off, start the engine and let it run until you can feel the upper radiator hose getting hot. Watch out for the engine cooling fan(s). By this time, the coolant level inside the coolant surge tank may be lower. If the level is lower, add more of the proper mixture to the coolant surge tank until the level reaches the FULL COLD mark on the coolant surge tank."

I looked at it again a few hours later, and the level is slightly below the FULL COLD mark. Is this normal? I looked at where i was parked and saw no leakage or fluid puddles.. so strange...what do you guys think it could be? a small crack or leak in the coolant tank?

more details:

Last time coolant was touched was about 4-5 years ago, my mechanic flushed it and re-filled it. I havent touched it since then.

I woke up this cold morning and checked under hood and the level was same as the last time i checked it, a bit below the cold mark. I'll attach a picture shortly

 

Ignore the yellow line please, it came with the photo.

The black line is where i filled it up to, and the red line is where it sits as of this morning. I will check it again when i get home.

 

I’d feel around the engine bay and beneath hoses and see if you can find the leak. Very common the water pump leaks, but not as aggressively as you’re indicating. See if you can visually find the leak….

 

You will typically notice about 1/4" or so level higher when hot than cold. Could be a little more - point is that hot and cold levels are different. If you were low enough to get an air pocket in the engine, I would expect the first time or two to have a greater delta because more would have been drawn into the engine when it cooled.

 

The expansion tank should be half full, COLD. Check it and add as required before every drive (engine COLD) until it stabilizes.

I bet you don't have an owner's manual. Buy one! Also buy a AIM, all the service/overhaul manuals for your year and download the appropriate vehicle information package from www.gmheritage.com

Coolant should be changed, (drain radiator and open block drains underneath the ignition shields at the bottom of the block) about every five years. Use Zerox G-05 in a 50-60 percent blend with DISTILLED water. Cooling system capacity is in the owner's manual, service manuals, and AMA specs.

Duke