NEW!!! Service Bulletin for Engine Knocking at Startup T-SB 0012-10

Thanks for this info! I've been reading through all these "bad gasket" posts and replies trying to find the info that best represents what I'm dealing with before making my own thread.

So this is basically what's happening with mine (2010, 200k miles) shaking started light at startup, now it's violent but smooths out after a long drive. Dealer said it's a blown rod and said I need a new engine (didn't seem like they knew about the head gasket issue) and quotes cylinders 3 and 4 only had 30-40psi compression. I drove to Raleigh when I found a Prius specific mechanic (1 hour drive) and it drive just fine. That mechanic is thinking it's the head gasket problem and quoted me $3k for the fix.

My main question is - is it worth it? The used car market is awful and the Prius may not even be worth the money it takes to fix. And we're not even 100% positive the engine isn't blown (although the new mechanic can't replicate the engine shaking, of course) or that it's the head gasket. So I'm just not sure what to do at this point.

So I made an account to talk to you guys! Thanks for the thread.

 

I wouldn't dismiss the dealership's diagnosis without further investigation. Protracted neglect of lown head gaskets can lead to bent piston arms (aka "blown rod"): coolant leaks into cylinder due to failing head gasket, piston comes up trying to compress the air/fuel volume but struggles due to (uncompressible) coolant, stops short, and piston arm bends.

Has the EGR and intake ever been cleaned? If so, how recently?

 

I have not done the EGR yet myself. I would have considered it more except for how violent and how often the engine was shaking. And then when the dealership said it was losing compression, I figured it was something bigger.

That said, I'm definitely not dismissing their diagnosis. I mentioned all this to the mechanic that has the car right now. The only real reason I'm thinking the piston arm isn't bent or broke is because the engine did vibrate or shake the entire hour drive to the mechanic. And the mechanic can't get it to shake at all now

 

My number two has zero compression as in you could crank all day and would never see the gauge move

 

I would also think like the Camry later models I don't know the AF engine or something You just buy a short block with those You don't even bother machining and fixing and what have you You buy a short block redo your head if it's possible assemble it and go

 

I had heard that it has to do with moisture/condensation in the manifold and not carbon. I am no expert , but that is how it was explained to me.

 

Does the shaking happen at every start up? Or only when it's very cold? And how long does it take to smooth out? It sounds like after all 4 cylinders are firing correctly, the car operates smoothly with no problems.

 

It's all due to bad design mostly. Many members know it here already but essentially in the 3rd gen the PCV valve design was such that it would allow blow by (engine oil) to leave the PCV and enter into the throttle body housing. Over time that oil would make its way up the intake manifold and cause multiple issues.

Removing my intake manifold you could see excessive oil build up in the bottom of the intake manifold, air holes leading to EGR pipe were begging to accumulate oil, and the head where the manifold attaches was absolutely crusted with oil.

The head gasket issue has been theorized many times over, no one is 100% sure what causes it. We know that the head gasket is heavily abused in a prius due to rapid heating and re-cooling. Some theorize that the EGR design is causing excessive heat build up, I'm not sure I buy it personally but an ounce of prevention is worth a pound of cure.

The head gasket typically causes knocking because coolant makes its way into the engine cylinder and the knocking you hear is incomplete combustion. The engine rods are slamming against an in-compressible solid and therefore the liquid must be expelled. The engine smoothing out is cause by the coolant being evacuated from the cylinder. Left untreated you can have bent rods or thrown rods. etc. etc.

 

Well, Gasket Masters postulated that.

There is an interesting coincidence: the head gasket failures reported here are predominantly at cylinder one or two, and when cleaning the intake manifold owners are finding the EGR capillary passages totally clog at cylinder one first.

 

It is hard to tell because cyl 1 and 2 intake from EGR are the farthest. But it is true that the head gasket problems related mainly how the car was driven. In city or highway, how many cycles on and off.
Cleaning the EGR valve and makes the intake manifold EGR gas balance, update the ECU for the EGR management, and waterpump condition check are important.

 

Can you tell me more about updating ecu for egr mgmt?

 

Unfortunately not. You need to come to your local dealership and ask for a software update. I believe the update was released before 2016. You also can put your VIN number in the Toyota website or make a Toyota account there. You will see the whole history of the car. In the USA, we do not have to be the owner. VIN number alone is enough

 

If you have Techstream, you can look at the calibration code for your ECM, and see if it is at least as recent as the one recommended for updating to in that TSB.

It's been noted here that the same ECM calibration update is recommended in two different bulletins, one where the EGR valve is replaced, one where the manifold is replaced, and neither bulletin says you have to replace the other thing. So I am guessing what's updated in the firmware isn't directly tied to a specific valve or a specific manifold, but just improves some control algorithms in general.

 

Maybe EGR software update was/is related to replacement of the EGR valve with revised one. There was some speculation here about that.

 

As far as we know, no update on the EGR, only on the intake manifold. The software is related to how much the valve is opened and when by ECU.

We still need to clean the intake manifold regularly and i believe we all know that under the throttle body, there always be some oil from PCV valve mixed with gasoline vapour. Fortunately, that oil does not effect how the engine run until the EGR small passages is blocked.

 

The oil at the bottom of the intake may be only a portion of what the PCV system delivers? Perhaps a significant amount is atomized vapour, passes right through?

 

There is a TSB that announces an intake manifold part number revision, and calls for updating the ECM calibration to N at the same time. And there is a TSB that announces an EGR valve part number revision, and calls for updating the ECM calibration to N at the same time.

N is the same in both bulletins. But the bulletin for the manifold says nothing about changing the EGR valve, and the bulletin for the EGR valve says nothing about changing the manifold. They just both call for updating the ECM firmware, and to the same version.

Hence my guess that the firmware revision contains nothing that is actually specific either to the revised valve to to the revised manifold.

 

Could still be a connection. Especially if that software update is only called for with either of those components being updated. Interesting.

 

Whatever is changed in the firmware revision, it is clearly able to work ok if you have the older manifold, and able to work ok if you have the older valve.

 

Reprograming is necessary no matter what new parts you put on. If it still works, no need to change it, just clean them. The intake manifold revision is to fix rattling issues in cold winter from ice formation in one of the passage if I am not wrong.