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OVERHAULING A PRIUS ICE

Discussion in 'Gen 2 Prius Technical Discussion' started by Dxta, Jun 27, 2017.

  1. Dxta

    Dxta Senior Member

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    everyone. Want to appreciate your efforts in proffering solutions to some of the problems I have had with priuses I have worked on.

    I have got a Prius 2008, that's got 100, 863miles on it. It shortens oil more than necessary, getting to the level I have to top up the oil with more than 3quarts of oil.

    The valve gasket seal has being replaced, and there isn't oil seeping out from the valve covers any longer.

    Crankshaft oil seal, and the seal between the interface of the eCVT and the ICE, isn't leaking.

    My conclusion now is to overhaul the engine.

    Question is, I need some advice on precautions to take before embarking on the job.

    Thanks everyone.
     
  2. bisco

    bisco cookie crumbler

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    not sure what you mean by precautions, but there are some great threads here on engine rebuilding with write ups and pics.
    all the best!(y)
     
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  3. ChapmanF

    ChapmanF Senior Member

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    There's a great thread in the Gen 3 forum about overhauling a 2ZR engine, but if you want to try the same job on a 1NZ, there's an eensy little difference you'll want to know about.

    2ZR has hydraulic valve adjusters. Easy peasy. There's 16 of them, they're all the same, they're probably fine after cleaning up, if any need to be replaced there's just one part number to buy, you replace, nothing else you need to do, they adjust on their own, done.

    1NZ has select-fit bucket lifters (not even shims!) in 35 sizes. You adjust the valve train by measuring all 16 clearances and selecting the right new bucket size for each one to get the clearance right. If you are the factory and you have an adequate inventory of all 35 sizes right on hand, that's easy and you just grab the ones you need and you're done. If you are not the factory and you don't have a $5k+ inventory of spare bucket lifters to pick and choose from, you have a project delay between the time you get everything reassembled to where you can measure your final clearances, then order the wretched lifters, then wait for them to come in. Could they have thought of a worse design for DIY if they were paid to? Maybe, but I don't know what it would be.

    That'd be one of the reasons most people's response to a 1NZ overhaul project is "shoot, have you noticed how cheap the complete used engines are?"

    -Chap
     
  4. 69shovlhed

    69shovlhed Surly tree hugger

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    I suspect used engines aren't that easy to find in lagos...
     
  5. 05PreeUs

    05PreeUs Senior Member

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    Check the PVC system before you dive into an overhaul! These engine are TOUGH, unless badly abused by a gross lack of oil changes or overheating, at 100k (miles or km) you should not need to tear it open for anything.

    Now, no OEM is perfect, but this is a Toyota.
     
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  6. Dxta

    Dxta Senior Member

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    I really want to thank you guys for your various inputs. I just concluded the overhaul or rebuild of that engine (1NZ-FE) yesterday, and this was what I learnt:

    05PreeUs: Have checked all that prior to opening up that engine.
    When we did open up the engine, to our surprise, this was what we saw after inspecting the engine:

    1.Piston rings, and oil control rings were worn(I meant the ring gap ends were beyond specification).
    I'm still surprised how that could be, since the car is a 100+ thousand mileages.

    2.All the rings(compression and oil control), were all not at the right positions (the 12-3-6-9 rings positions on the piston lands were positioned directly at the gorgion pin locations of the pistons. And that allowed more oil consumptions and excess fuel consumption.

    3. Piston crowns and both exhaust and intake valves tops on the cylinder head, showed signs of engine oil seeps into the combustion chamber.

    4. Spark plugs, intake and exhaust valves also had ash yellowish kind of deposits on their surfaces.
    This made me to conclude that the yellowish deposits might be as a result of carbon and engine oil accumulation that has undergone exposures to tremendous amount of heat.
    On some of the piston crown also, we noticed kind of blackish carbon deposits on em.

    **********
    I really never knew that OEM parts could be fitted wrongly from the factory. Or is it possible for compression and oil control rings to shift from their original positions after installation from the factory? I heard it doesn't shift, because the pistons only engage in reciprocating motion.
    *********

    69shovlhed: Well, you could get that engine there, but you the problem is, no one is sure of the mileages of those engines. And coupled with the fact that Prius parts in Lagos are very expensive, compared to a highlander or Camry hybrid.
    To be on the safer side, I preferred to overhaul that engine e, with new OEM parts.
    We replaced all the metal and beqrings,; O-seals, rings, water pump, chain, etc.
    In a used engine, those parts may be on their way out already.
    Though this project took us a week to finish, because we had to be very careful of the connectors of components.

    ChapmanF: Refer to my response to 96shovlhed.

    bisco: I meant, before someone undertakes such a project as an overhaul of such, what care, or precaution should one adhere to?
    For instance, ensure blablabla is done, etc kind of.

    Thanks everyone once again for your contributions
     
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  7. Dxta

    Dxta Senior Member

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    Those are the pictures of the car, and the parts replaced?
     

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  8. ChapmanF

    ChapmanF Senior Member

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    Thanks for the update! What was your approach to setting the valve clearances?

    -Chap
     
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  9. bisco

    bisco cookie crumbler

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    thanks for the write up and pics, well done! have you owned since new, or is it possible it was mistreated in a prior life? how is the gas quality there? are you up and running?
     
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  10. Dxta

    Dxta Senior Member

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    I didn't set the valves. There wasn't any noise or of some sort coming from the valves area at the top. I don't think there's any need setting the valves. They're controlled by the VVT-i mechanism.
    Correct me if I'm wrong.
     
  11. Dxta

    Dxta Senior Member

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    The car was bought from my second country, the "USA", used.
    The oil shortages has being like that ever since.

    As regards, MPG, I did a test drive this evening, and returned awhile ago, didn't bother to check that on the energy monitor. Would do that tomorrow.

    My observations after the test drive:
    1. Check engine/VSC/BRAKE/ABS lights suddenly came up, and brakes suddenly became ineffective.
    Solution: scanned the car, and got a code related to hydraulic system fault.
    Checked all the lines, discovered rear left had brake fluids leaking from the brake shoes.
    Brake shoes were worn, and had to replace them, and some of the seals there.
    Those lights were cleared with the scan tool, before driving the car.

    2. While I was driving with the AC system on, and stuck in heavy traffic, there was intermittent red triangle caution sign with a temperature sign displayed on the MFD. Within some seconds, it disappeared. That tells me there's a temperature rise somewhere in the system.
    Solution: Would get the car scanned tomorrow for codes.

    3. Car feels smoother more than ever before now.


    Thanks
     
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  12. Dxta

    Dxta Senior Member

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    A note of caution pls. Anyone engaging in an overhaul like this, must ensure.all connectors are properly connected back from where they were removed. That would prevent the battery from running out of juice, when it has to power the ICE.
     
  13. Dxta

    Dxta Senior Member

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    ...let me reintegrate. The connectors at the throttle assembly are two, in the gen2.
    The one with lots of wires going into the throttle assembly outside of it, is easily seen. But there's one behind the throttle assembly, hidden that you can't see. So you'd have to search for it with your hands, or use an electrical wiring diagram.
     
  14. Dxta

    Dxta Senior Member

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  15. Dxta

    Dxta Senior Member

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    Legends:
    First picture: Prius being testdriben in traffic
    .
    .
    .
    Other pictures are the leaky brake shoes/seals and the replaced parts.
     
  16. bisco

    bisco cookie crumbler

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    thanks! please keep us posted.
     
  17. ChapmanF

    ChapmanF Senior Member

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    VVT-i is responsible for the valve timing (on the intake side only). It has nothing to do with valve clearance.

    Valve clearance in the 1NZ engine is adjusted by select fit of the lifter buckets that sit between the valve stems and the camshafts. The manual specifies the correct clearances, you measure the actual clearances, and subtract. Then, for any that are out of the allowed range, you measure the thickness of the lifter that is used there, and replace it with one of the correct thickness. (The engine does not use shims; the adjustment is by replacing the lifters themselves, which are sold in 35 sizes, in steps of 0.02 mm. The tables of sizes for intake and exhaust are on the fourth and fifth pages of the section on valve clearance adjustment in the repair manual.)

    The 2ZR engine used in the 3rd gen Prius does have automatically adjusted valve clearance, but a 2008 does not.

    In my own experience with a 1NZ at 198,000 miles, I found five out of eight exhaust valves, and one out of eight intake valves, to be out of the allowed range (all on the tight side, not loose). All the rest of the valves were in the allowed range but still on the tight side of that range, they just hadn't exceeded it yet. Apparently this is not an engine where the clearances get looser with age (or at least mine didn't).

    If they tended to loosen with age, the worry would be more for valve train noise. If they tighten with age, the worry is more for eventually burning them, if they don't rest on their seats for enough of the cycle to transfer their heat to the head.

    So it sounds like you just didn't devote any of your attention to valve clearances at all? Did you at least make sure all the 16 valves and lifters got back in their original spots?

    -Chap
     
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  18. Dxta

    Dxta Senior Member

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    Wao! Didn't know that Chap! Thanks for the info. But mine weren't making any noise, so left them. If it did next time, would take off the buckets and see what's in there.
     
  19. Dxta

    Dxta Senior Member

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    Would post the MPG stuff later today as I embarked on the next round of test drives today
     
  20. Dxta

    Dxta Senior Member

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    Returned from my final test drive today, and while the AC system was ON, and driving some miles, the triangle caution sign came on, at the same time, a thermometer sign in red. Check light also was on.
    Scanned the car using tech stream, got a P1116 code.
    Relaizsed the inverter coolant was some what low, and had to bled it of air bubbles.

    Prior to when the engine wa overhauled, there wasn't such a code, and triangle caution sign.

    I checked the connectors to the heater temperature sensor by the inverter, they were all properly connected.
    Have cleared the codes after bleeding air bubbles from the radiator and inverter coolant systems.

    Meanwhile, here are some pictures of the MPG.
    Pls correct me guys, if in wrong in my calculation, and how do I do it the right way?
     

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