Blown Head gasket rebuild....@297k

What are the green dabadoos, break-in grease?

 

Lucas Assembly lube.

It was in a pic prior.

 

Yes, necessary and very well thought out by danlatu!

 

What were the specs for chain stretch, and how did yours measure up?

Did you happen to get a count of the links, or get any picture, before you buttoned the timing cover back up, that would allow counting them? I can see there are 18 teeth on the crank sprocket and 36 on the cam sprockets, and I think I could almost count the chain links from one pic you posted, only the chain guides make some of them hard to see.

Because the manual says to and it's their first try on a particular model and they assume if the engineers didn't say the easy way would work, there must have been a reason, so they're reluctant to try?

That's one of the best takeaways from what you've posted here, that upward removal is possible. It seems much less daunting to contemplate.

Did you have to loosen any transaxle mountings, or was there enough room to swing the engine sideways and clear the input shaft and bell housing?

Still waiting eagerly to find out how easily you lower it back in, with that big fat 16-valve head on top.

I wonder if that plastic impeller, that from a recent photo I take to be molded in two pieces then stuck together, and coming apart with age, looks like something that could be practically 3D-printed in one piece? Of course I don't know anything about the temperature ranges of the typical printing materials, or compatibility with hot Toyota coolant.

If it's like the first gen, it's not even separate shims; it's one-piece lifter buckets machined in 35 different sizes. You need enough on hand to be able to select the 16 you need in whatever sizes your assembly measurements indicate. (Unless you want to place the order only after reassembling and reaching the measurement step, and leave the car apart while they ride the boat from Japan.) That's a lot of inventory if you want to be in the game, especially at Toyota prices of, like, $11 each. Pretty well rules out DIY.

So that's a very good reason to like the hydraulic adjusters on the 2ZR. Makes working on your engine practical again.

Speaking of piston coatings, the New Car Features manual mentions the low-friction resin coating used on the piston skirts. Is there still any sign of that after 297k?

-Chap

 

Looking closely at the head gasket and comparing the holes in the gasket to the size of the water jackets and opening in the heads has me confused. It appears that the small holes in the gasket are being used as an intentional restriction to slow coolant flow in/out of the head. guessing it has to help heat retention in the head to promote more efficient combustion. But the holes on one side of the gasket still look too small to me.

 

Sounds like hydraulic adjusters are just great, until they aren't.

Toyota, take a page from Honda, use screw adjusters. Gives guys like me (splashing around in the shallow end) something constructive to do...

 

Do you have the original gasket to compare the aftermarket part to?

 

My first car had a Mitsubishi 4G32 engine with screw adjusters that I think I could complete a valve adjustment on in something like 20 minutes start to finish. At the time I think I viewed it as a sacred adolescent privilege to be exercised as often as possible. My next car was a Mazda with hydraulics, and I somehow found myself with less time on my hands than I remembered from high school, and I didn't mind not having to fuss with them.

The Mazda got stolen and I ended up with a Ford 2.8 V6 with screw adjusters, and I found those very frustrating to get right (or, easy to think I had right, crank down the locking nut, and then find to be wrong). Now, there could be a couple possible reasons for that. One could be that the Ford screw adjustment was really more difficult than the Mitsubishi. Another could be that I was a dozen years older and more likely to notice how my performance on a task differed between my imagination and reality. I do remember that during that period I envied a friend who had a Ford 289 that came, even back in 1965, with hydraulic adjusters.

But for DIY purposes, I guess I could live with either kind. The screws, if they need adjustment you adjust them. The hydraulics, if they get stuck you soak them in penetrating oil or replace them (and that probably happens a lot less than screw adjusters needing adjustment).

The one arrangement that just throws DIY out the window is the 1NZ fixed bucket lifters. You mean I can't adjust my valves if they need it without first measuring the clearances and then buying special-order parts and waiting for them to come in? Or, I just need to have 16 ✕ 35 = 560 of them on hand before I start, for a cool up-front outlay of six grand, to be sure I'll be able to choose the sixteen I need?

Now, a more actuarially-minded person would probably say, well, it's really unlikely you need all 560, just buy a smaller bunch of them in a Gaussian distribution favoring the middle part of the range, and most likely you'll have the ones you turn out to need, and put some of the money you save under the mattress against the small risk that you need to order some others and rent a car for a month while they come in.

And an approach like that works great at the factory, where they even have massive data on the statistical distribution of which sizes they need how often, and I'm sure that's exactly how they do it. But for DIY? Not very practical.

I think I can be perfectly happy with hydraulics that might need to sit in some penetrating oil every couple hundred thousand miles or so.

And anyway, there's an extra cool thing about these hydraulic adjusters. In both my old Mazda and my friend's older Ford, they lived on the ends of the moving rocker arms, and were probably at least as heavy as a screw and locknut, maybe heavier. In the 2NZ, they sit stationary in the head, where their inertia doesn't contribute to the forces on the valve train. Nifty....

-Chap

 

Could the gasket design be because of the electric water pump? With fan driven pumps the flow varies with engine speed. Is the Prius water pump a one speed unit or does it vary speed as needed? With expierence working on chevy v8's the giant water ports in the Prius head look like overkill, but the small holes in the head gasket still intrigues me.

 

The pump is variable speed between ~2600-3000 rpm as I have observed with Techstream. This being from cold start through closed loop up to mid-190's F temp. Not sure if it turns faster at higher temps, but it is indeed speed variable.

This is a big takeaway for me, Dan. I've been assuming that a head pull/ oil pan drop will allow the pistons up and out as I've seen done with Corolla engines. However, having followed the thread, I'm not as put off by the engine pull as I've previously been. Anyone know if the Gen 2, 1NZ-FXE uses the same long block design?..

 

1NZ is the same in terms of having the two-piece bottom, one a small stamped pan, the other a casting that can't be removed or replaced without separating the engine and transaxle.

-Chap

 

That may be the fly in the ointment though. In the 1NZ, there is no separate housing for the main seal: it is pressed directly into a round bore whose top half is in the engine block and bottom half is in that "lower bell housing", or "oil pan no. 1" as the Gen 1 manual calls it.

So if 2ZR is that way too, any time you take that lower housing off, your old main seal is toast, you need to press a new one in after reassembly, and I don't see that working out with the engine on the tranny.

-Chap

 

I sure appreciate all the explanation and pictures of this adventure. A lot of my questions about the gen3 engine is being answered, but one answer I haven't seen yet is about the rings, especially the oil ring. The new rings you put in are different from the originals and I'd like to know if they are the recommended replacements and are they being used in the newer Prius? If so, when did they change to the new more open oil ring? If not, why not. I'm thinking the more open oil rings would have helped lessen or eliminated the oil consumption problem.