My 1998 nissan maxima is overheating. My heater runs cold and around 15 min it starts to overheat as I'm driving, but if i switch to OD off it starts to cool back down. I cange my oil today and it looks like chocolate milk. Google and result said coolent leak... Im gonna buy some blue devil tomorrow and replace my thermostat.
just wondering if y'all know why OD off does that to my engine?

 

Stop driving your car immediately and replace the water pump. Members here have replaced theirs and there are a few videos on YouTube showing how it’s done. If you’re not comfortable dealing with the timing chain, then take it to someone you trust.

How long and how many times did you drive it while overheating? Hopefully you didn’t blow the head gaskets.