2015 1.8L rattling at low rpm, head gasket?

GPT for the win. It all makes sense, but again I doubt a clogged EGR is the root cause of blown heads. If your rings are leaky, that's 100x worse than poor exhaust gas recirculation.

Other causes of blown heads are things like:
* not changing your oil
* water pump failure
* coolant loss and overheat(most common cause)
* cracked radiator (see coolant loss)
* bad gasket design (Subaru)
* blocked water jackets

I'd put most of those ahead of EGR blockage.
Blocked EGRs mostly cause poor engine performance in my experience.

 

Probably a good thing I was skeptical of that great advice in hindsight tho, right? I could be out there swearing into the gloom and breaking off head bolts...

 

Good advice thanks.

Conpression was 120psi across all 4 cylinders. Did the test dry and didn't bother with wet test because I think its within spec. Also all 4 are the same which implies roughly even wear.

Coolant hasn't dropped and I don't see any obvious leaks.

When you say run a DTC do you mean a Toyota Techstream test sequence? I have a generic bidirectional scan tool, but so far Prius support hasn't been the best in my limited experience.

Spark plugs and coils were replaced and all the permanent OBD codes vanished pretty quickly. The engine hasn't rattled a bit since I did the fixes. Also cleaned most of the intake passages and EGR. That reminds me let me check the resistance of my old coils...

 

Ahh so you're still waiting for the "I told you so" about the cheapo coils and plugs? You can have it in a year, but by that time I'll have salvaged like 12 OEM coils from a junkyard. Let me know if you need a set.

 

No, I'll be back for sure so rjparker can tell me I've got a blown head again and make his dumb joke again

 

https://m.youtube.com/watch?v=tdIFYJvCCdM

I Do Cars did a teardown of blown 2ZR-FXE