I need advice
About two months ago I noticed my coolant was low and I heard a knocking on cold start ups in the morning. Went to Toyota to get it looked at and feared head gasket. They couldn’t confirm it was a head gasket because it passed the pressurized test and they couldn’t see any coolant in the engine. They said it was most likely the problem. They topped off the coolant and sent me on my way.
What I’m confused on, since they topped it off 2 months ago, the coolant levels haven’t dropped and the cold start knocking stopped. At was until 2 days ago. The knocking started back up and a little bit for violent. Yesterday it knocked and the check engine light went on. Codes read cylinder 1 and 2 misfire. I’m gonna get another diagnostic done tomorrow.
It’s a 2012 Prius model 2 with 178,000 miles. It’s been past due for a tune up. It only had one previous owner before me at 130,000 miles. What’s more likely? Head gasket or spark plugs and EGR clogging? No white smoke, no coolant drops from what I check, no drop in mpg. I was quoted 6k for a head gasket(obviously Toyotas price), but I don’t wanna waste money if it’s a tune up/ EGR cleaning problem.
Any advice or insight would be much appreciated