Cold-weather startup rattle revisited

Discussion in 'Gen 3 Prius Technical Discussion' started by ChapmanF, Dec 21, 2019.

  1. ChapmanF

    ChapmanF Senior Member

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    My 2010 at around 150,000 miles has started, for the first time I've noticed, in the recent cold weather, exhibiting the cold-start rattle elsewhere extensively discussed.

    I am not sure whether it ever had the updated intake manifold installed per T-SB-0010-12. I guess it might not have, given it was only a TSB, not a recall, and maybe it never happened while the previous owner had it. My VIN is earlier than the production change.

    My 2001 Gen 1 also developed rattly cold starts in its later years, but I don't think that gen ever had a manifold update issued.

    I know I have seen some opinions here that the puddle of gloop that forms at the bottom of the intake manifold is a contributing factor, so this morning before the first start of the day, I used a brake bleed cup and vacuum pump to suck out the gloop. The total was about this much:

    gloop.jpg

    I find myself wondering if just that amount of gloop can really be getting sucked into cylinders ... it's in a part of the manifold that hangs very low compared to the intake ports. And my understanding has always been that a Prius manifold pretty much always has a small puddle of gloop at the bottom.

    A different early explanation was from Kore971, who apparently compared the old and new manifolds, and said that the new one had ridges added in the EGR passages, which could baffle water that accumulated in the EGR pipe from being sucked into the cylinders. I guess I could see that happening more easily, as the EGR passages are smaller, and kind of lead from the pipe directly to the intake ports. (On the other hand, my Gen 1 did also get rattly in its old age, and Gen 1 had no EGR.)

    The engine did start rattle-free after I had vacuumed out the gloop. But the outside temperature had also gone from the teens (fahrenheit) the last few days, to the forties today, and it never did rattle in the forties anyway. So I'm not sure what to conclude.
     
  2. trentofdestiny

    trentofdestiny Master Finagler

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    Make sure to take note of whether it was fully warmed up before the cold soak and subsequent first start of the day. I can normally make mine do it on command if I start the engine, move the car, shut it off, and not let it run more than a minute or two. The next day it will rattle.


    iPhone ?
     
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  3. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    Have you cleaned out the EGR cooler? I am a little concerned, as the start up rattle was blamed on excessive moisture/fuel in the intake... also, Prius with headgaskets failing and ingesting coolant have exhibited the same rattle. You're at the mileage for a potential head gasket problem, based on other owners experiences and stated mileage on this site.

    I have owned 4 Pri - A mixture of Gen 2 & 3, and of varying mileage. My 2007 had 217,000 miles when I sold it last month, and was noisy (valvetrain) when started cold. It went away after a minute or two. My 2012 would only "cold start rattle" if I started it up to move it around the driveway, and shut it right off. The next start up would cause a real ruckus. My 2015 does not cold start rattle at all (so far).
     
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  4. tvpierce

    tvpierce Senior Member

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    I've questioned the theory before that the pool of fluid that collects at the bottom of the intake manifold is being sucked into the cyclinders, and causing cold-start-knock. It's just physically impossible. It's a cold, viscous liquid. It can't defy gravity and migrate up the intake runners -- particularly while the throttle is closed and the air flow over the fluid is at its lowest point.
     
  5. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Would it be possible for atmospheric condensation within the manifold to cling to the "ceiling" surfaces of the manifold? If so, wouldn't it have a natural path to drain into the intake ports?
     
  6. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Is there an assumption at work here, that the goop you're seeing at the bottom of the intake manifold is all there is? Perhaps there's double that amount, all initially airborne mist, and the cold/stable stuff at the bottom of intake manifold is just the portion that condensed?

    With an oil catch can in place, that pool is gone for me. There's still a "sheen", but no accumulation.
     
  7. ChapmanF

    ChapmanF Senior Member

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    Well, it kind of seems like everything I've read on PriusChat about the issue has been a structure of assumptions holding up large cantilevered claims. I just wanted to get one more measurement in there that I hadn't seen made before.

    For example, some of the purported explanations I've read have to do with the physical effects of slugging incompressible liquid into the cylinders, while others have just been about the misfire-inducing effect of sucking the wrong stuff into the cylinders.

    I don't have a measurement at hand of the (assumed) mist concentration there in the manifold, but I might assume (again!) that what is in the form of mist may be compressible enough to not have the slugging effect of drawing in a liquid. It might, of course, still have an effect on combustion.

    Then there's still Kore971's observation about where the changes in the manifold were made. I haven't directly compared the two manifolds myself, though.

    Hmm, I haven't poured out my dollop of gloop yet. If only I could remember from chemistry the right setup to measure its vapor pressure at 18 F....
     
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  8. bisco

    bisco cookie crumbler

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    don't feel bad. toyota engineers are still scratching their heads
     
  9. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I have a vague hunch (from low-res cross sectional pics of the intake manifolds) that the change (or at least one change) was that the EGR passages went from one long gallery that feeds directly into four capillaries (one per port), to a shorter main gallery, splitting into two intermediate size tunnels, then into four capillaries.
     
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  10. mjoo

    mjoo Senior Member

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    Toyota engineers left the room and are working on Gen 5 and Gen 6.
     
  11. Nor'easter

    Nor'easter Member

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    On another thread, I am wondering out loud of the solution to this cold start misfire problem is simply a smaller spark plug gap.
     
  12. Cosmo Tigato

    Cosmo Tigato Active Member

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    When I took off the Intake manifold on my 2011, I looked down into the intake valves and there was liquid trapped above all the closed valves
    upload_2020-1-12_11-26-51.jpeg

    I wonder if that builds up every time you turn off the car.
    Then on start up the liquid gets dumped in to the cylinders and causes....
     
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  13. Grit

    Grit Senior Member

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    Condensation?
     
  14. mjoo

    mjoo Senior Member

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    Valve seals?

    Pixel XL ?
     
  15. Cosmo Tigato

    Cosmo Tigato Active Member

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    Could be a mix of
    Condensation?
    Fuel from the last shot from injectors?
    oil blow by?

    This is all a guess on my part.
    I put a paper towel down there and soaked all of the liquid. I did NOT taste it:eek: and it did not have a particular smell that is why I guess a mix.

    That car is in excellent condition, I found that liquid when I was cleaning the EGR and Intake manifold
    The manifold did have a bout 2 tablespoons of liquid at the bottom (148,000 miles)
    Strange but this 2011 never knocks or rattles.
    So I don't think that liquid causes rattle or knocks or .....
     
    #15 Cosmo Tigato, Jan 12, 2020
    Last edited: Jan 12, 2020
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  16. Mendel Leisk

    Mendel Leisk Sand Pounder

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    You may have solved an ongoing puzzle. Note that the odds of knock at start up seem to increase, if at the last start up, the car was run only a moment, quickly shut down.

    The spring emptying of my oil catch is about half oil, the rest a creamy oleo, mostly water, with a bit of gas?
     
    #16 Mendel Leisk, Jan 12, 2020
    Last edited: Jan 12, 2020
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  17. Eddie25

    Eddie25 Member

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    Didn't someone recently mention cleaning their injectors as their fix for a frequent startup rattle?

    Would dirty injectors cause them to leak?
     
  18. ASRDogman

    ASRDogman Senior Member

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    If they are dirty, they could leak, as they are under constant pressure.
    I "think" it was Cosmo Tigato, but not 100% certain of that.
    He just rebuilt a motor. He said he had a good spray pattern, which is likely,
    but they can still leak if the seat inside is dirty. He cleaned then, and no more knock.

    There is a pressurized bottle you can hook up to the fuel rail and pull the relay/fuse for
    the fuel pump, then you run the engine until it stops, as the bottle will be empty.
    Then replace the fuse/relay. After disconnecting the bottle. :)
    Or you can remove them and use a tool to hook up to the injectors and clean them under pressure.

     
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  19. ASRDogman

    ASRDogman Senior Member

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  20. Cosmo Tigato

    Cosmo Tigato Active Member

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    Could a catch basin be installed under the manifolds lowest point like a screw in hard bottle?
    all the vapor and liquid would just drip down and accumulate in the bottle and not get sucked back up...

    This is in addition to a catch can for the PCV

    Thoughts... Maybe something we could look into and invent?
     
    #20 Cosmo Tigato, Jan 12, 2020
    Last edited: Jan 12, 2020
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