Still Losing Water

Just take out your plugs and put it inspection camera up one and two and you'll see the droplets generally It's very common in this setup I have no idea why it seems that EGR gets blocked and maybe internal combustion temp goes up and smokes the gasket have no idea but it's a horrid setup but this is all happening after most people should be out of the car really it seems like 150 160 most people are generally out of technology like this pretty quickly generally speaking because things start to happen. It's not your dad's old Toyota where you just pegged three or 400,000 and that was it You can still drive more but you are getting a new car and the old Corolla went to your kid brother or whatever.

 

How many miles on the car, and how long have you been losing coolant? How much coolant have you added, and how often are you adding it?

Does the high temperature warning light come on.

Does the engine run rough, or is it noisy after a cold startup?

 

The leak into the cylinder is slow and often seals itself in seconds during warmup. But there can be enough to foul a plug after the engine cools off and coolant pressure exists. Tom’s borescope test depends on coolant pressure on a cold engine using a quality dual view borescope. A clean piston is enough proof. Your symptoms alone on this engine is usually enough.

A compression test shows nothing on these engines. Normally a coolant combustion gas test will pass as well until the white smoke pours out the exhaust in an advanced stage hg failure. At that point it will rattle during engine on at stoplights regardless of engine temp. Then it’s guaranteed replacement engine time. The only step further is a broken rod and holes in the block.

Like this shock and awe late stage hg

W’s shock and awe did not work out so well 20 years later - Prius engines don’t like it either

 

2’nd the miles question.

ever cleaned the EGR and intake?

 

The coolant leak into the cylinders fouls the plug and causes the misfire. The only time an egr can cause a misfire is at idle if the egr valve is stuck open and exhaust gas is easily flowing in at low rpm’s. Rare with the revised 2013 and up Toyota egr valves.

The easy way to dismiss the egr system prior to the parts cannon:

In this video he has a stuck egr valve and the misfires went away when he blocked the flow for testing. He prefers to replace the egr valve with the new revised version and the updated software load.

Watch until the end where he references the difference between a stuck open egr valve and a head gasket.

 

Finding things on this forum takes time
Clean everything still knock when pressing on gas pedal | Page 2 | PriusChat

If I revised the above I might add 1b “Used Gen4 engine as is into Gen3” but concerns are the same as any used engine plus changes needed in the cooling system, wiring and the use of gen3 egr, intake, controls and wiring harness. Not a lot of 100% great experiences reported here but quite a few overheat and persistent code issues.