Another EGR thread

Caked up is better than clean enough to see aluminum color on parts of a piston. In your case the cheap borescope is non-conclusive for a head gasket leak.

You can not just look unless you see a pool of liquid or one cylinder is shiny and the rest are carboned up. You pressurize the cooling system to 15 psi with a cold engine and use a dual view or articulating scope to observe the cylinder walls and head gasket. Then you wait for one or two drops. Hopefully they don't come.

Do not pour liquids into the cylinder regardless if its Marvel or not. That is hydrolock and junk engine time ready to happen.

 

For an ecm update you need to buy access to the Toyota TIS system and have the latest Toyota Scanner software running on a PC with a hardwired Mongoose usb to obd2 interface. Its cheaper and safer to let Toyota do it. I would not worry about it until you have a trouble free engine. Then consider updating the ecm software.

Latest Global Techstream+ required along with a $545 Mongoose interface. You supply an adequate Win11 pc.



Global Techstream+ download and two days authorization is $80. Includes calibration files for updating your ecm or other ecus.



Better to let the dealer do it unless you are a shop with continuing requirements of this kind.

 

Typically cylinder one (left end when facing engine from front of car) is the first to get coolant from failing head gasket. It’ll look exceptionally clean.

 

Yeah clean indicates possible coolant cleaning. It's similar to deglazing a frying pan. You need a better borescope, and it should be able to look "over it's shoulder", to see the head gasket seam.

Initial failure is typically cylinder one, which is furthest from the EGR inlet on the intake manifold, and the small EGR passage at port #1 tends to be the first to totally clog with carbon.

I would check the condition of the coolant too, looking for gloops, evidence of stop-leak product. The manufacturer of one such "product" says it can be flushed with a 50/50 mix of water and white vinegar, fwiw.

 

With protracted neglect of 3rd gen head gasket failures the failure progresses to the other cylinders.

 

Won't help.
The crud in your cylinder bores is not the problem.
Running the engine with coolant in the bore can (and will!) lead to hydro-locking - which will illuminate the "change-engine" lamp.

 

Me too. Getting an in-depth understanding, one that sticks with you, seems to require learning it yourself. When answers are handed to me, they tend to vapourize quickly. One personal example, trying to sort out a chord progression, when plunking out a a pastiche of someone's song on piano. If I'm flummoxed I'll go to Guitar Tabs (chords are chords), and there they all are. But the ones I got from there tend to be the ones I forget, or stumble over.

 

So far there is no clear diagnosis. Often a pro does a diagnosis of exclusion especially when there are no codes on an intermittent problem.

Again, overheating on a gen3 rarely happens before a hg problem and usually never happens because the symptoms are so severe that even pro mechanics may think a rod has broken or a hole in the block has occurred. But "conventional logic" does not compute when it smooths out ten seconds later and may run for weeks without obvious coolant loss or overheating.

MUCH later after foolish owners have spent $1k-$2k on plugs, coils and injectors and have temporarily reduced symptoms with pressure relief tricks and sealant, holes in the engine and bent rods can happen. So while the new guy is trying to make sense of it and can't believe Priuschat advice or won't use a shop with a quality borescope, he is often ruining the engine with overheats due to a sudden loss of coolant, white smoke and or newly ventilated engines.

I call that the "Hey Walt" moment...

South Main Auto
Excellent Borescope Footage at 6:50
Honda Misfires on Coldstart Only

This video is obvious but illustrates the quality of borescope needed. A gen3 often has one or two drops when cold and with coolant manually pressurized. Of course there has to be coolant in the cylinder/head coolant passages.

 

3-part video #30 (currently bottom of this list) here, is @NutzAboutBolts head gasket saga. Worth a watch. He's working on his own car, so really taking his time, cleaning everything as well. IIRC he is or was working as a mechanic in a Toyota dealership, and I'd think in that environment his approach would be much more expedient. Anyway, a very leisurely/thorough approach.

The flipside is gasket masters, a couple of links here.