I just changed my thermostat today on my '99 Pontiac Grand Am. My car had been running hot. At first I'm pretty sure I over filled the antifreeze so we drained it completely and put new 50/50 in. It was still running hot so I decided to change the thermostat. Just got finished and now when I start it, it makes a whistling noise. Along with some type of smoke coming from the exhaust pipes. Please help!!
If it is more of a squeel than a whistle you may have spilled antifreeze on to the serpentine belt. The anti freeze is making the belt slip. Is the smoke coming out of the exhaust pipe or off the pipes in the engine bay? If anti freeze was spilled onto the manifold and pipes it will smoke until it burns off.