Chevy S10 Leaking then Not Leaking

I was driving around today, and for the first time since I got my truck (last year) I used the A/C on high. I pulled into a parking spot and was fidgeting in my car, when someone walked by and said, “You know you are leaking right?” I got out and on the far front passenger side of my truck, there was a massive puddle of pink fluid falling to the ground. I popped the hood, and saw that the coolant tank was almost empty. Luckily there was a Napa Auto parts right across the street. I ran and got some premixed anitfreez/coolant. I filled the tank up to the fill line, ran the truck for a few minutes both with the cap on, then the cap off. It stopped leaking. I drove it home, keeping a close eye on the temp gauge, and it only rose half a tick mark. Now I don’t know what to do next… I have very limited experience with vehicles and therefore am somewhat hesitant to work on it on my own. Any help would be appreciated!

Was the fluid that used to be in your coolant system pink? Could it be pink windsheild washer fluid? What year is the truck? Were exactly was the fluid leaking from?

You need to have the cooling system pressure tested to determine where this leak is coming from. Once the cooling system is under pressure, finding the leak should be easy. Most shops will do this fairly cheap. My father had a local independent shop do this on his Cavalier a couple years ago. They charged him $15 to tell him his water pump needed replaced, so he took it home and replaced the water pump himself. Once you know where the leak is coming from, you can make the call as to whether or not it is a repair you want to attempt on your own.

It would also be nice to know the model year, mileage, and engine of your truck. This info will help us help you.

Have you checked the coolant level in the radiator? If not, check when the engine is cold.

An old radiator cap may not be able to keep the cooling system pressurized and the coolant will boil over. Radiator caps are inexpensive, I replace the cap on my 2000 Blazer at each coolant change (~3 years). Use a Stant Model 10230 or 11230 (Spring-Center type).

The 4.3 V6 has problem with the GM intake manifold gasket leaking. Usually this is indicated by a slow drop in the coolant level with no visible leaks. Just something to watch out for in an S-10.

Two years ago, the side tank of the radiator cracked and started leaking. Fortunately the crack was near the top so the engine did not overheat.

As the other posters suggested, have the cooling system pressure checked to determine the source of the leak.

Autozone has repair guides for 96 to 99 S10’s and 2000 to 2005 S10 Blazers and Trailblazers. I use both guides to troubleshoot my 2000 Blazer. It’s good reading.

Good luck,

Ed B.