Camshaft housing hold down bolts

Discussion in 'Gen 3 Prius Main Forum' started by donzoh1, Feb 9, 2019.

  1. donzoh1

    donzoh1 Junior Member

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    Just when I thougbt the difficulties were done!!!! I was torqueing the camshaft bolts. I used 12 ft lbs for the 10mm black ones and 20 ft lbs for the 12mm, 15 bolts holding camshafts in place. There are 2 more 12 mm bolts, one near cylinder 4 which seems the same size as the other 15 and a shorter one near cylinder 1 behind the exhaust cam. All 17 of these have the number 11 stamped on top. This last shorter bolt broke during installation but the torque was nowhere close to the 20 ft lbs of the other bolts. Torque seemed to increase slightly but then dropped off. I was able to loosen and remove the whole bolt but it looks twisted at about the halfway point where it is noticeably skinnier.

    One other issue is that the bolt at first did not want to engage threads in the head. I think this was from a little RTV sealant that I eventually removed with a small screwdriver. The first 12 or so revolutions were easy after this.

    I'm guessing this bolt might have been overtorqued at some point but I didn't notice any defect before installation. I got a new bolt at the hardware store and it's hardened but I don't know whether it will take 20 ft lbs
     
  2. cnc97

    cnc97 Senior Member

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    These bolts are TTY, should be sourced from Toyota. You do not want to throw just any bolt from the hardware store in there.
     
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  3. donzoh1

    donzoh1 Junior Member

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    I'd agree that not just any bolt that fits will work. The one I got is stamped 10.9 on the head which is a metric equivalent to Grade 8, which are frequently used in automotive applications. I still might check with the dealer Monday on whether they have one or when they can get one.
     
  4. ChapmanF

    ChapmanF Senior Member

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    TTY in #2 is "torque to yield", meaning bolts engineered for the specific application, so that when you have properly installed them, they are stretched by a precise amount. The stretch applies the intended force between the mating parts.

    I remember that the manual gives specific instructions for measuring the stretch of removed head-to-block bolts before deciding which ones to reuse. I don't remember whether I saw similar instructions for the cam deck bolts, though.
     
  5. donzoh1

    donzoh1 Junior Member

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    I had improperly torqued the new head bolts in that I did not apply the light oil coat on threads before installation. I talked with the felpro tech people and then removed the bolts. I measured them and they were all within the factory new length tolerances so I installed them again correctly. I have not seen a maximum bolt length for the camshaft housing bolts although that may exist. I think the cylinder head clamping force is much more critical than that for the camshaft housing. Then again, I'm not an engineer.
     
  6. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

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    I recall being in a meeting once, over mis-ordered bolts, a fairly large quantity, and a grade other than optimum. In the end the engineers ok'd it, but there was a fair bit of consternation. I think the consideration that everything had generous over-design allowed us to go with what we had.
     
  7. edthefox5

    edthefox5 Senior Member

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    It is a good idea to chase any bolt hole with proper size tap first. Scraping stuff out with a screwdriver is not how you do that.

    Good idea to lubricate the bolt hole than put a tap though it then screw in the bolt gently noticing any difficulty’s as it goes in. If lots of debris in the hole you should be able to feel it then using choke cleaner blow the debris out and start over. Only then use a torque wrench to sock it down nice a slow. I usually check any torque setting on a wheel lug.

    Friend of mine at work didn’t listen to me and snapped a bolt clean off in the head of a ford pos 4.0 motor.
    Had to take the head to a machine shop $150 later.

    Quality brand tap.
    Quality brand torque wrench not a pos harbor freight wrench.

    Patience.
     
  8. donzoh1

    donzoh1 Junior Member

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    I went to the junk yard and got the bolt from a Scion XD which shares the 2ZR motor. A Pontiac Vibe was there as well but it's motor was gone. The dealer only wanted 2 bucks for a new bolt but also couldn't get the bolt for 4 days.
     
  9. cnc97

    cnc97 Senior Member

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    That will work.
     
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