2013 1.8l Prius cylinder head gasket replacement

Could it be the MAP sensor connector??

Ah maybe not, that looks to be 3 wire:



Knock sensor wire?

 

It you can get a couple of good pics, I can see if it matches the ones on my Gen4 harness. It should as I didn't change any sensors on my swap and everything fit.

 

It seems to me that cylinder 1 was the hottest since it was the only piston that expanded enough to polish the walls and because there's fewer carbon deposits. This makes sense since the EGR channel to cylinder 1 is the longest while the channels to cylinders 2,3,4 get progressively shorter in the gen 3. A longer channel would have slower EGR air flow and be easier to clog with EGR soot and oil. Eventually more deposits accrue in cyl 1 EGR channel vs. cyl 4 EGR channel.

As the EGR flow becomes unbalanced it would cause more EGR to flow into cylinder 4 than cylinder 1. This would cause cylinder 1 to run leaner and hotter while cylinder 4 runs richer and cooler. A richer/cooler cylinder generates more soot in the combustion process (cylinder 4). More soot leads to faster depositing in the EGR system and the EGR merry-go-round accelerates.

What's interesting is that the hotter cylinder 1 was not the cylinder leaking with antifreeze.

The Gen 4 manifold has EGR channels that resemble a tree to help prevent the EGR flow from becoming unbalanced. This is to realize equal lengths (restrictions) across all EGR channels.

 

I think the gen 3 manifold revision (maybe standard from 2012 model year on) also does that tree thing. Also, seems like gen EGR passages have much greater "amplitude", diameters close to double.

 

Do you have the part #?

Pixel XL ?

 

McGeorge Toyota shows the same part number for 2010 through 2015, but maybe it's the revised one.

Intake Manifold - Toyota (17120-37054)
2010-2017 Toyota Intake Manifold 17120-37054 | McGeorge Toyota Parts

interesting too is this comment:

• Replaces: 17120-37050, 17120-37051, 17120-37052, 17120-37053

 

Ah, post 5 here, has Toyota pdf regarding the intake manifold revisions.

Warranty extension for the egr | PriusChat

 

The fixed manifold (-37054) may have come out after @donzoh1's 2013?

This is the oldest article (dated June 22, 2014) that I could find mentioning -37054.
Prius, Prius Plug-in, Prius V engine rattle/misfire fix: no longer available?

 

My take-away from this thread is engines with old-style intake manifolds may need more periodic EGR circuit cleanses than the popular 100k advice. The intake manifold may need shorter cleaning intervals than the EGR cooler to prevent the unbalancing of EGR flow and ensuing head gasket leak.

 

I’m sticking to 50k miles and pair it with the engine coolant swap.

 

Sorry for the late response, I kept forgetting to reply. You are correct, I forgot you did a leakdown test and heard air hissing from the piston rings. Plus you have already had the head inspected and it passed. If that is the case, the air hissing from the piston rings (esp from cyl 4 )would explain the reduced compression. I am not sure what happened, but perhaps when the head gasket blew - the engine overheated and the rings got cooked? Or perhaps this engine is simply worn out?

Considering how much time you've spent on this already, you may be better off doing the Gen4 engine swap. I think your only option at this point is to either rebuild the bottom end or start with a different short block (preferably from a 2015 or from a Gen4).

 

Is he still leaking coolant? Otherwise a couple of long piston soaks could be a more appropriate next move?

 

I guess it depends on what his timeline is. If the piston rings are worn and causing a loss of compression, then soaking is unlikely to provide any significant improvement.

 

Do you really think the piston rings are worn at 127k on a hybrid with probably 80k actual engine miles?

Pixel XL ?

 

We do not know the operating conditions. If the car was used strictly on the highway then the engine could have been in-use for the entire time.

The rings (or even the entire bottom end) could be worn for a number of reasons. At least to me, the goal at this point should be to find the most efficient, reliable and cost-effective (depending on your definition) way of getting this car back into service. In my opinion, that would be either a Gen 4 swap or even a new short block from Toyota. For me, downtime is a huge concern so I may view things a bit differently than others...

 

There are two sensors that the leads need extended. And the lower hose needs reworked. Or use the Gen 3 head on the Gen 4 block and it’s plug and play.