2013 1.8l Prius cylinder head gasket replacement

I figured out at least part of the coolant/oil mixing problem...sort of by accident. I was getting ready to put the cylinder head back on and I first added coolant directly to the engine block just to have more coolant where it belongs on startup. Immediately, coolant poured from the engine block onto the harmonic balancer. I was not preciously aware of the coolant passage from the block to the water pump and had not put any RTV around that port on the timing chain cover. Coolant had apparently leaked directly into the timing chain cover and into the crankcase. This doesn't account for the compression loss though, and I'm hoping to have that aspect of the problem fixed by tomorrow.

 

I put the head back on and did a variation on a leakdown test. Since I don't have the leakdown test kit, I inflated my 2 gallon air tank to 115 psi. Then, I hooked up an air line to a given cylinder with the piston at BDC. Each cylinder was pressurized for 3 minutes. Pressure measured at that point in cylinders 1 thru 4 was 75, 75, 62, and 45 respectively. Then, I added oil to each cylinder and pressures went up to 100, 85, 70, and 78. Curiously, as air leaks from the cylinders, the sound is much louder in the crankcase than in the intake ports. Also, it's kind of a crackling noise. The motor is not level so the rings are sealing at the rear, not at the front. I think I will test again tomorrow with a couple more ounces of oil in each cylinder to verify how much of the compression loss is either head or head gasket.

 

Head was resurfaced and vacuum tested. Coolant was leaking into cylinder 4 making morning startup rough.

 

Camshafts are not yet installed so all valves in the motor are closed. Normally, leakdown tests are done with a piston at TDC on compression stroke for the reason you suggested. Camshaft installation will cause some valves to be open at any given crankshaft position.

 

Please elaborate on how bent rods could contribute to this problem. I did observe 1 and 4 at TDC and 2 and 3 at TDC when the head was off. They moved in those combinations as the crank was rotated and seemed to be right at the top of the cylinder together. I ddin't measure with a straight edge and feeler gauge but maybe that's not a bad idea next time I have the cylinder head off.

I repeated the above outlined leakdown test with pistons at TDC. Cylinders 1 thru 4 are 100, 74, 71, and 68. These results are comparable to the results at BDC. Both of these tests show somewhat higher compression levels than the prior BDC test with no oil on the cylinder walls which points to some ring/cylinder wear. Cylinder 1 lost 15 psi and the other three lost about 45 psi during the 3 minute interval. This is perplexing though as cylinder 1 had the only visible polishing in two areas of the otherwise cross-hatched cylinder walls. Mileage is around 145K.

Listening during the compression leak test, I noticed most of the noise emanating from the crankcase. I could hear a crackling noise in addition to the escaping air which I think was oil bubbling near the piston rings as air was bypassing. If the leak was either valves, cylinder head cracks, or gasket, I would think it would be a whistle or hiss, since there's no oil or coolant in that area yet.

 

Not sure whether I mentioned this but in addition to the polished cylinder wall sections, piston 1 had white deposits on the valves while the other three had brown or dark gray coloring.

 

The photo above is the cylinder head with cylinder 1 being on the right. Exhaust valves in the other cylinders are whitish gray. Any ideas on what the discrepancy in valve color means or whether that's related to the better compression numbers in cylinder 1?

 

My thought was that combustion in #1 was incomplete, caused by inadequate misting of a faulty fuel injector. Maybe unrelated to the compression issue?

 

Ooops, broke the wire connections on the plug going from the front/middle of the engine block to the water pump motor. I think this connector tells the water pump when to come on. The broken connection is between a black plug and two wires, one black and one white. I'm considering a dealer or junkyard for this part but am open to other options. Also, if possible I'd like a picture of the connector showing where to connect the white and black wires.

 

Actually, I think it goes from front of engine block to throttle body or something. The water pump connector has more pins.