Engine Gasket Problems

No hybrid thermal cycling.

 

Gasket Masters says he's seeing head gasket failures on high mileage Gen 4s. He made a short YouTube video about it.

 

I guess you have to expect problems at high mileage

 

There's been a few 4th gen head gasket failures reported here. Some of them the head gasket was fine; mechanic saw coolant loss, assumed head gasket failure, but it turned out to be exhaust heat recovery system leaking. One guy did have a head gasket failure, and that was after exhaust heat recovery issue, and driving with low coolant and overheat warning light.

 

??

 

My car had 301,000 miles on it. I was planning a time to replace the gasket,
BEFORE it became a problem. Then I could fix it in MY time and not worry about
having to "get it done". And not have to rush around to get parts.
It just didn't work that way.
But it's done now! I put 763 miles on it the last two days.
I put 322 miles on it yesterday.
I put 441 miles on it today.

And I've driven 3012 miles since replacing the head gasket. Still running smoothly!

 

Welcome to the increasingly large club...

 

????

 

The blown hg club

 

yea, but mine is at 300,000 miles. Not the 150-200,000 miles.
300,000 miles is a lot of miles. A lot of cars never make that.

 

T24A-FTS is one of the new toyota engines where they got rid of EGR and instead did a pair of three-way catalysts installed in series to control emissions. I would suspect they decided a more expensive catalytic converter was a better strategy than using egr.
Unfortunately, Prius is all about thermal efficiency so we still have EGR.

https://toyota-club.net/files/faq/18-03-20_faq_df_r4_eng.htm
Scroll down to the last 20% of the page to see the below article with photos.

Ecology

• PCV (crankcase ventilation) - with a special separator, which should make oil separation more efficient and reduce the oil deterioration. PCV valve is built-in between the cylinder head and the intake manifold to rid of the extra vacuum hose.


1 - ventilation hose 2, 2 - PCV valve, 3 - ventilation case 1, 4 - intake manifold.


1 - air cleaner hose 1, 2 - intake manifold, 3 - ventilation hose 2, 4 - cylinder head cover, 5 - cylinder head, 6 - cylinder block, 7 - crankcase, 8 - oil pan, 9 - ventilation case 1, 10 - PCV valve. a - fresh air, b - blowby gas + fresh air, c - blowby gas.

• EGR (exhaust gas recirculation) - inevitable evil, which serves (in theory) to lower the combustion temperature and to reduce the nitrogen oxides in the exhaust gas, but in practice it provides only common problems with carbon deposits in the intake paths and on the valves. Soon let's see whether it is possible to shut off it without consequences (at least, there is no feedback by EGR temperature sensor here).


1 - EGR valve, 2 - EGR cooler

The gases taken out downstream the catalyst pass through the channel in the cylinder head to the cooler and then to the valve. The EGR valve (also water-cooled) is driven by a stepper motor.



Then the gases flow to the EGR manifold, which evenly delivers gases into each cylinder.


1 - intake manifold, 2 - EGR pipe, 3 - EGR valve, 4 - EGR cooler


So it looks like the new solution is:

Post cat egr (cleaner), larger and smoother intake egr passages, and a larger central position entry into the egr passages in the intake manifold now to get more even flow from shorter more balanced passages.

Big benefit over the old ones where pre cat egr and entry on the far side of the intake manifold resulted in quicker clogging and more uneven clogging to the far ports. The results will probably be the car will probably clog the egr far far slower than the gen 3's, hopefully after the usable life of the car is finished.

I also see they added a mechanical vacuum pump to the new motor. That will be helpful for the other issues the cars seem to have.

 

4th gen seems to have trouble free EGR. On the backs of 3rd gen beta testers.

 

4th gen is post cat so i imagine that also helps a lot. Makes you wonder about putting that exhaust manifold on our cars for the post cat egr. Sounds like a lot of work though so i won't be doing it.

 

4th gen EGR components on 3rd have been problematic. You're still upstream of the Cat, and the car's computers aren't programmed for it.

 

Yes, original battery. I have just over 305,000 miles now.

 

Gasket problems are usually caused by numerous engine cycles. It isnt unique to the prius, but the prius is a hybrid so having the engine turn off and on numerous times in a single drive will eventually wear it out faster than a regular car. As well as loosening the headbolts ever so slightly from constant uneven expanding and compressing from heat cycles.

Not sure how EGR correlates to the headgasket having problems, unless excessive pressure in the cylinders is made to overpower the torque on the headbolts, thus opening the gap, and thus chipping away at the gasket till a hole is formed. At least thats how i picture it happening.

Realistically theres more factors involved, but for mine, i think pouring paint thinner to try and clean my cat was the straw that broke the camels back. I ended up having headgasket issues in the next day or so, so i dont think its a coincidence. I believe pouring fuel injector cleaning could potentially also cause it to fail similar to mine, but maybe not. I have dunked my old gasket in thinner just as a test and the black coating came off a lot easier scrubbing it off. I imagine thats how my hole was made in the gasket.

 

Why do you guys parrot that when the gen 2 priuses run the same and have no head gasket issues?