Curious find on why some coolant mixes turn sludgy in cold weather

Tbh, I heard that using the wrong antifreeze can gel up and block the whole cooling system if it gets too chilly.

4 comments

4 Comments

Mixing the old green ethylene glycol with newer orange propylene glycol can cause a jelly-like substance, not really sludge. It happens because the different silicate additives react when they get cold. I saw it once in a truck that used a universal mix after a flush, and the heater core plugged solid.

morgan_burns961mo ago

Well damn, I always thought it just made sludge. Your explanation about the additives clumping when cold actually makes way more sense. Guess I learned something today.

smith.elliot1mo ago

So what do you do if you get that gel? I mean, @zara_murphy45 is right about it not being sludge, and it's a real pain to flush out. Maybe try a chemical cleaner made for that before you start taking hoses off.

zara_murphy451mo ago

The silicate drop-out in older green coolant is what @morgan_burns96 was getting at. It forms a gel, not really sludge, because the additives fall out of solution. That gelling is what actually blocks things when the temp drops.