Any Gen 4 Owners Out There With Blown Head Gasket ??

When I drained our engine coolant (on our 2010, fall of 2020), I didn't touch that heat exchanger, but I was sore tempted. As they mention it's the lowest part of the system. From my log, I drained roughly 4 1/4 liters. I'd suspect there was another quart lurking in the exchanger.

 

Yeah, I was going to change my wife's coolants (2017 LE) (radiator/hybrid) but she hasn't even got 30,000 miles on there, yet, and it still looks brand new. Kudos to Toyota for using the same coolant for everything....genius!!
I checked her maintenance records and the only recall was in Dec 2018 for "wire harness and reprogram sonic ICS intl sensor."
I only remember having to top off her coolant level once and it wasn't even 1/2 a cup...so not too worried about it.

 

@Willl I'd like to be placed in line incase @AmazingFacts backs out

 

Has everyone seen the 2023 GR Corolla with that 3-cylinder turbo and 300 HP? Maybe trade in my 2021 AWD Prius for one? (Just dreaming, though, the GR is definitely not a daily commuter car, especially at 12 mpg when the turbo is fired up!)

 

Just don’t…

 

I might do that...

 

Well, this is an old thread, but I have a 2016 Four Touring with 90K miles and was just diagnosed with a blown head gasket. Started to blow white smoke and the coolant level dropped. Took it to my local independent shop which has a guy certified to work on Priuses and he confirmed the blown head gasket.

Fixing it is going to run north of $4,000. I haven't gotten the actual estimate back yet but that's what they said. This price includes having the head machined. I asked them to price a new engine just for kicks and will see what they say about that.

I guess there is nothing else to do but bite the bullet. This will be my last internal combustion engine car, I've already decided that. When this dies for good I'm going full EV.

 

I would seriously have them check the exhaust heat exchanger. I'm betting it's that

 

I will definitely ask them to check the exhaust heat exchanger. They are closed until Monday. I don't know what they exactly did to confirm it was a blown head gasket. They just confirmed by suspicions but I don't exactly know what tests they did. Symptoms were:

1. Engine temperature warning light flashing then stayed on (how I knew I had a problem)
2. Car blowing white smoke out the exhaust
3. Car sucking up coolant. I refilled the coolant reservoir (the large one for the main engine) and it ran dry after driving about 3-5 miles.

 

Wow that's aggressively fast to lose coolant. Also most people with the heat exchanger issue don't have the flashing engine temp light either

 

These symptoms don't nail down the head gasket as the culprit. There are tests that will show if it's the HG. These symptoms could be the HG or the catalytic converter heat exchanger. So far, based on reports I've seen here on PC, the heat exchanger is the more common problem.

 

If coolant loss was due to head gasket failure you’d likely have bad shaking at start up. AND: nobody seems to have blown a 4th gen HG yet. More likely to be exhaust heat exchanger failure.

 

Im no mechanic but couldn't one just bypass the Cat Heat exchanger to see if thats the culprit (and drive it to see if the issue is still there or not)? This would be similar to those bypassing the heater core in an older car?

 

No shaking of any kind. Car drives entirely normally for what little I drove it. Basically commuting back and forth to work which is 5.8 miles of gentle suburban driving that takes 10-15 min so engine barely even gets hot in that short distance. After I noticed the issue I refilled the coolant and after driving home from work the reservoir was drained again but the engine temp light didn't go on. So it is furiously burning coolant but no other symptoms. The overheating light might have gone on if the coolant level had dropped too far.

In any event, first thing Monday morning I'll be talking to them and asking them to check the heat exchanger before ripping the engine apart. That video upstream is a good link to send them if they have questions. It is the same exact car as mine.

It is a really good local mechanic shop that has a guy who works on Prius but that isn't their main bread and butter. They work on all cars basically. So many not know the nuances of the 4th Gen Prius. But they are minutes from my house and 100x nicer to deal with than my local Toyota dealer which is way out of town and a giant hassle to deal with.

 

I’d place my $$ on the heater bypass vs head gasket. Your symptoms don’t sound like headgasket on these. Most mechanics that primarily work on ICE only vehicles assume white smoke, coolant consumption = head gasket. Not this vehicle with the heat exchanger on exhaust. Check it first. Much cheaper fix.

 

Yes, yes you can.

 

Yes, that's exactly what my mechanic did. I drove it that way (with the HX bypassed) for a month while we waited for the replacement part to come in.

Also, mine sucked down coolant like it was its job. Very fast leak, and initially misdiagnosed as head gasket failure. Glad I got a second opinion.

 

I very strongly suspect (like others), that this is coolant leaking into the exhaust system via the heat exchanger and NOT head gasket. You have a 2016 model (like me) at a mileage (~90k) which is a textbook example for this problem. The TSB re this is here https://static.nhtsa.gov/odi/tsbs/2019/MC-10166037-9999.pdf

You may be interested in my experience 2016 - complete power loss / breakdown | PriusChat

and there are multiple other threads:
Engine coolant inside catalytic converter | PriusChat
TSB: Coolant leakage at front exhaust pipe (Prius & Prius Prime) | PriusChat
Gen 4 Coolant leak | PriusChat

It seems to be the main major issue with early gen 4 models.

 

It would make sense that a leak in the exhaust would lose more coolant. Probably a much bigger hole and it would leak continuously rather than only on the intake stroke. I've never seen one, but if the exhaust is hot enough to vaporize the coolant before it exits the tailpipe, I'll bet the white cloud is impressive.