New Head Gasket!

Yeah it depends what you're doing.

For just-in-case, I like to disconnect the 12 volt neg cable before lifting a caliper off its rotor. Otherwise it's way too easy (and a catastrophe) to trigger a pressurizing episode, which'll likely pop out a piston. Also makes it easier to avoid an excess pedal travel warning.

 

Tell me like I'm 5 how does the egr make head gasket faill

 

The EGR gasses are supposed to help keep chamber temperatures around 200 degrees lower then they would normally be. When they aren’t there, one or more cylinders run hotter then they are supposed to, and the coolant sensor doesn’t detect the increased temps.

 

The members here who believe that it does have seized on the fact that EGR reduces in-cylinder combustion temperature (which is absolutely true, that's what it's for, to keep the temperature cooler than where NOx emissions form), and have pinned onto that true fact the question "ok, so with EGR obstructed, is the un-reduced combustion temperature high enough to murder head gaskets?" and assumed the answer to be yes.

It's not an insane question, of course, and the answer could be yes, but to date nobody promulgating that theory on PriusChat shows any interest in finding out whether it is or not. It's just stated to be yes. (A little bit implausibly, given that head gaskets are also used on engines that don't use EGR at all.)

That assumption about raw temperature isn't the only mechanism that could be involved in a connection between EGR obstruction and head gasket issues. Detonation ("pinging") is an established possible effect of insufficient EGR, and that can be hard on the gasket. The ECM automatically retards the ignition timing if it knows the EGR flow is insufficient, in order to ward off pinging. To know whether the flow is insufficient, it has a Manifold Absolute Pressure sensor, and can see the pressure rise when EGR is let in. The engine also has a knock sensor, giving it an additional warning to retard the timing if any pinging starts to happen.

But there is only one MAP sensor, and there are four separate EGR passages in the manifold, so there could be a case made that if some of those are more obstructed than others, there could be some cylinders at risk of pinging even if the overall EGR flow is judged ok.

That also is unproven (so far on PriusChat, anyway), but might be a more plausible mechanism than the overall "temperature gets too high" story. It would still need empirical work to find out if it holds up.

One attractive point about it is that removing just the intake manifold, and checking/cleaning those passages, is way less work than examining the EGR system stem-to-stern. And you can use Techstream and the car's existing sensors to check on the overall EGR flow without having to take stuff apart, leaving those four separate manifold passages as the only bits needing direct examination if the overall flow looks ok (because, again, results from the single MAP sensor can't tell you everything about those).

 

It’s also pretty easy to check (for carbon build up) the inside of the stainless steel bent pipe running between intake manifold and the Exhaust Gas Recirculation valve. That’s @NutzAboutBolts video #16 linked in this thread:

Nutz About Bolts Prius Maintenance Videos | PriusChat

Videos for manifold cleaning, and full Exhaust Gas Recirculation cleaning are also linked in the same thread.

When cleaning the intake manifold it’s usually the Exhaust Gas Recirculation passage at cylinder one that’s most clogged. And when head gasket fails (heralded by misfire code), it’s usually cylinder one, or between one and two.

More info here:

Bad Flywheel | PriusChat

 

$23,000

 

Haven't heard of it going that high yet, unless they're selling you need a new vehicle off the showroom floor.

Recently a toyo tech showed me a text message from an advisor/colleague at an old dealership, they had quoted someone 4300 all in. Not sure if that included a new head or what, and seems excessive either way. But this could just be fake news, and nothing more.

 

I just got a couple on NON dealership quotes for our Prius v that most likely needs a head gasket. One at a hybrid specialist ( carspecmn.com ) up in the Minneapolis area, and one at a local shop. Both were a hair under 3K...which is about what I was expecting.

Talking with the carspecmn.com guy was interesting. He said they have seen quite a few head gasket issues lately on Gen3 based vehicles. Seems as the Gen3's are aging out, the HG issue is becoming more and more prevalent...which makes sense. Note that carspecmn DOES include a new EGR cooler as part of the job...so they obviously know it's an issue...as they should.

 

I tend to agree that the EGR to Head Gasket connection makes logical sense in a way...but I still haven't seen any conclusive evidence.

Ironically, our 2012 Prius v that needs a Head Gasket has had all of the maintenance done on it that was supposed to prevent Head Gasket failure ( see thread in my sig if curious ). Also, it never has consumed a discernible amount of oil.

However, our 2010 liftback has had NONE of that same maintenance done on it...and was fine ( until it was totaled in an accident a few weeks ago...haha ).

 

Wait a sec, I missed that: are those threaded holes? Similar to the brake rotors? That is good to know, hopefully would restrain the pulley enough to retorgue the bolt.

 

EGR lowers the temperature and cylinder pressure. Lowering temperatures is just what it's used for to reduce NOX.

Yes those separate EGR passages get clogged unless the manifold is cleaned every ~50k-100k miles. When they plug they clog unevenly causing some cylinders to get more EGR and other cylinders less EGR. I'm more concerned about this as it can lead to warping the cylinder head from differences in pressure and temperature between cylinders.

 

I couldn't put a motor in a Prius for under $4,000. Are you sure they're replacing the engine? Are they ASE certified?

 

Why would you buy a motor when you can just pop a head gasket back in? All in it was 250 bucks and a days work. Unless you are dumb enough to drive the misfire to a hydro lock situation and throw a rod. There is nothing wrong with these motors, it is a bad head gasket, regardless of what caused it. 200,000 and the motor purrs like a kitten again.

 

But the catch can is the best idea I have ever heard of. The further away from the engine the better. Mine is behind the left headlight. The car burns no oil now and the intake is dry. But the junk in the catch can? I have no idea what it is, but all I can say is it is some kind of nasty byproduct of gas. When I change the oil, it is barely golden at 5000 miles versus before the catch can, the oil was dirty brown. I empty the catch can twice in 5000 miles and it is half full of junk each time.

 

@SFO thanks for putting a like on this, because I was going to say: reached down there, with an M8x1.25 (thread size) bolt today, and yup: it's threaded and that's the size. Pretty ubiquitous size: same as brake rotors and drums have. Which is real handy:

It should be easy to fashion a "special tool", say a hockey stick handle with a couple of holes, at the same spacing, put a torque arm on the pulley that'll jam against something, say the drive shaft.

I appreciate you can knock the bolt loose with an impact, or hold it with a braced wrench while someone blips the engine, but for subsequent torquing to the spec (140 ft/lb IIRC), you want to just restrain it.

 

I think I'll put my OCC in the trunk!

 

Because it's a 16-hour job, not one day.... and these motors start burning oil at about 120,000 and it only gets worse as the motor gets older

 

If you need 16 hours to do a head gasket on a gen3 Prius. You are taking your time or you shouldn’t be turning wrenches. This is the easiest head gasket I have done. Pulling the engine you have cared for and replacing it with a junk yard engine you have no history; is insane. I had 192000 on mine, oil changed every 5000 miles, and it did not burn oil like people report. If you did not care for your engine, that’s on you. Even used, if you pull the valve cover and the engine is clean, a head gasket is all you need. Regardless of what took the head gasket out, it is only a bad head gasket. Period. Throwing an engine away for a bad head gasket is just stupid. And dropping in a used engine without putting a new head gasket in (going through the engine) is playing Russian roulette.

 

And…. Mine just did the IPM failure, causing the engine to constantly run. That little engine; with a new head gasket (10,000 miles) purred so smooth, I was shocked at how good it ran. The dealership could only find one thing wrong with the car. Condensation in the headlight. Toyota rebuilt the inverter for free ($2800 bill) and it is back to 100%. While I loved my bullet proof gen2, I adore my sunroof gen3.

 

You're demeaning and abusive.