EGR cooler nightmare event -- always check a used one for leaks before you install...

Short story: I took a running, zero issues 2014 Prius burning no oil at 148,000 miles and converted it to a blown headgasket.

Long story: I replaced my 2011 Prius EGR cooler 4 years ago with a cleaned up, used one. The 2011 Prius is going strong.

My 2014 Prius is headed to another state so, I decided to clean up the 2011 EGR cooler and swap it into the 2014. I completed the swap and immediately got a check engine light. It ran fine so I drove it , and started to see steam. Took the short connecting pipe off between the EGR valve and intake manifold and found coolant. Took things back apart and found a leak in the 2011 cooler. It did NOT have the leak before I cleaned it, but somehow, between my Draino and piano wire cleaning, I must have exposed or created a leak.

I cleaned up the 2014 cooler and tested for leak -- no leak. Put things back together, but still consuming coolant and sending out steam from the exhaust.

So the coolant from the defective EGR cooler must have caused my head gasket to fail.

Ugh. I converted a perfectly running vehicle to a junker. Guess I will be learning how to replace head gasket.....