cold start knock/rattle fixed

Classic hydrolock

 

The hydrolock failure is often delayed. First a minor bend of the rod. The attached piston still functions. Over a period of time metal fatigue and uneven cylinder wall occurs leading to a complete failure. Often with holes in the block. When the knocking and severe rattling starts it is time to move straight to head gasket diagnosis and repair. Not weeks of delay caused by incorrect dealer and forum diagnostics leading to egr cleanings, catch cans, plugs, coils, injectors and sealers. Most typically providing a temporary reprieve and happy face.

Low tension piston rings are the root cause and were epidemic in many models of the era. They allow excessive blowby which feed the egr and pcv systems. At some point they are obvious and create excessive oil consumption. Toyota acknowledged this problem early, repaired many free and updated new production by mid 2014.

Egr design and carbon buildup in gen3 hybrids are symptoms and not the root cause. Toyota has never acknowledged the egr as a problem other than software upgrades for gen3. The Corollas of the time using a 1.8 and egr don't exhibit unusual numbers of head gasket failures.

Thermal cycling of the gen3s makes a difference. These engines can temperature cycle the block and cylinders by 50f.

Toyota's gen4 redesign was implemented by 2016. Better pistons and rings. Far different thermal management of the cylinder walls including a special insulator. Improved cooling channels around the cylinders and heads. The egr was rerouted downstream of the catalytic converter to reduced intake hydrocarbons along with increased egr size. Intake and pcv design changes to reduce liquids pooling in the intake while improving combustion.

Sure egrs are a contributor but many with frequent egr cleaning still experience failed head gaskets. Sure any engine that overheats can blow a head gasket. But the Prius gen3 was a dramatic change to gain mpg but resulted in many issues (not all engine) which were not adequately resolved until gen4.

These days the best solution for a high mileage engine failure is a rebuilt engine. A used engine if you want to flip it.

We now have gen5 where mpg increases are slight but power improvements are huge.

 

So if you've got no oil consumption the EGR doesn't clog?

To be fair I think it's a symphony of screw ups. But my money's on the EGR design.

I can't see a design being a symptom.

 

Did they not use the same rings? My niece has a 2013 Corolla.

 

But how much did the level drop between your oil changes, and how far apart were the changes?

 

Corolla 09-11 had low tension and became oil burners.

Gen2s had a convoluted coolant strategy and some burn oil but they had no egr. I think gen2 was a better car overall especially for reliability. HV batteries in both gens created a new small business opportunity, many who have proven to be scammers or a waste of money.

 

One slight correction: Toyota has a revised EGR Valve for cold soak (extreme cold) cold start issue, although I have since lost the TS-B and part #s.

I’m probably the only one with the flash that has the older/original EGR valve…