Gen 3 Prius Engine Coolant Recovery Tank Pressurized, head gasket?

How many miles?

 

Coolant cap pressure is 19 PSI. It should release pretty quickly when the cap is loosened. But the cap could be holding extra pressure or the combustion gasses could be over-pressurizing the tank. Take the cap off and run your Prius in maintenance mode. If there are bubbles in your tank, the head gasket is the culprit.

 

This is the equivalent of holding a grenade in your hand after pulling the pin, but you have no actual idea when the explosion is going to occur. You have multiple warning signs of impending trouble. This engine as it stands is simply a running core at this point. If you have the resources at hand, move on them now, in my opinion.

 

Um, usually when an ICE fails it doesn't spread life killing shrapnel in every direction... No need to be an alarmist spreading unnecessary fears...

 

Maybe just an allegory?

 

My choice of description might be slightly alarmist, but I know from experience that “when” the failure occurs, it will be at the most inconvenient time that you can think of.

 

YES.

 

@PriusCamper : grenade cleanup on aisle 4 :

Transmission | PriusChat

 

Yeah... Fear of the unknown is always a valid reason for caution... But once you read the error codes and the unknown becomes known it's possible, in some cases, to temporarily live with the red triangle knowing that it's not going to disable the vehicle.

For example, I drive really old, rebuilt too many times battery packs to monitor how often the red triangle comes on from specific modules I'm on the hunt for. And the pack in my car right now has already had 7 modules replaced over the years and I'm reluctant to replace three more, hopefully my friends finds a way to buy the loaner pack in her car so we can retire this pack. About every 75 miles it'd throws a red triangle and I'd screenshot it and clear it with Dr. Prius while driving and just keep going, which is no big deal for me. Then as I had hoped, the situation deteriorated to the point it was throwing 3 red triangles a day. So I was going to pull the pack... Then, inexplicably... It hasn't thrown an error code all week over the course of 200 miles. Electrons are weird!!!

In other words, some of us are quite comfortable with a hand grenade without the pin in our hand as just another ordinary day and we've not much of a concern about being stranded because with experience you're more likely to find a way to safely make it home.

 

Such are the nature of our “experienced” Prii or Priuses, one day they are ready to give up the ghost, and the next, they act like it’s day one again.

All things considered, I’d buy mine again if I knew all that I would have to go thru.

 

The thermostat temp is listed as 180. So if you aren’t seeing signs that it’s open, then it might have failed. However, I can tell you the hottest temp I have ever seen in my car is 195. And that was after 4 1/2 hours on the highway at 65+mph. So if you aren’t getting any hotter, then it’s possible that yours is still good, and just not showing any flow.

 

Good for you for having a go at it!
And good on you for already thinking of all the peripheral parts that might be wise to replace while you're in there.
How much time are you able to give yourself? Do you have another vehicle to drive for as long as it takes to complete?

I've found I do my best work with first time repair learning when I give myself lots of time to be super thorough and clean and inspect everything as it comes off the car. That way when it's time to reassemble everything is super clean and it's like assembling a brand new car instead of an old worn out greasy grimy one. I enjoy the experience way more that way too. But I'm kind of a neat freak like that!

 

Running up a mountain will run the temp up real fast.

I do a partial grill block in winter, but make a point to pull it off if going up a serious hill.

 

This video has a lot of good tips. They have some cringeworthy table manners, and some bits drive me up the wall. Like how they'd applied Form-In Place gasket to the timing chain cover, before they even start filming the scene, and the guy stands over it talking for about 2 minutes, before they even get around to looking where it goes. Repair Manual says the stuff should be out of the tube and the cover back on the car within 3 minutes, and all the bolts (roughly 25) torqued withing 15 minutes. Anway...

Some repair manual excerpts attached:

 

Will you be replacing anything besides the head gasket?

 

Have you ever got temp data on difference between partial grill block vs no grill block?