Sunday while getting the coolant reservoir replaced I realized the threading on my reservoir cap was broken and rotted away. I placed an order for another one and continued driving with the old one. So Wednesday, I had the a/c on in some traffic and the car heated up to about 75% of the gauge. I parked it and turned it off, and then the coolant cap blew off and most of the coolant sprayed out.

I bought a new cap and refilled the system with g12 and distilled while running the heat, and let the car run for almost an hour. I gently sprayed the engine bay and wiped down everything that had coolant on it. After clearing some unrelated CEL's I started the car and let it idle for 15 minutes. Everything seemed fine but as soon as I got a few blocks away from my house this morning the CEL started flashing and a good amount of white smoke began to come out of the exhaust. After a few blocks it went away and seems to drive fine, but I haven't started it since.

The car has misfired on me several times before after clearing codes but I have never seen any smoke before. Could something have been damaged when it overheated? How can I check? Is there anything else that can explain this smoke?

Thanks in advance for your help.

 

I believe a flashing CEL means stop immediately and call for a tow.

Here is my guess - your head gasket blew and that white smoke was coolant which got into your exhaust. Once the pressure in the cooling system dropped there was nothing forcing the coolant into the cylinders anymore. Check your coolant and see if it is clean or if there is oil floating in the reservoir. If it is dirty and you see oil it is probably one of the head gaskets.