Coolant loss mystery

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by ilovegirls, Feb 25, 2021.

  1. ilovegirls

    ilovegirls Member

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    I have been chasing this for a few months and cannot find anyone with the same issue. I am slowly losing coolant. I checked the oil level and it's not in there. I checked the ground and it is not there. I checked the upper and bottom hoses and it is not there either. The coolant light has gone on but goes after 30 seconds. The weird thing is I'm finding drops of coolant on top of the reservoir tank. There is a drop in coolant so I just add more. Thinking it was the cap, the little plug, and the reservoir, I decided to replace it with oem parts.

    Things I have replaced:
    Reservoir cap- oem
    Reservoir tank- oem

    I checked the spark plugs and they look fine. No signs of foul plugs or corrosion.

    Where can the drops of coolant come from to end up on top of the reservoir?
     

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  2. jerrymildred

    jerrymildred Senior Member

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    When I zoom in on your picture, I think I'm seeking dried up pink spots in lots of places. Are you sure the water pump isn't leaking and flinging around drops of coolant?
     
  3. tankyuong

    tankyuong Senior Member

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    Your engine is burning it and turning it into steam
     
  4. ilovegirls

    ilovegirls Member

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    I didn't think of that. I did notice spots on the fender and stuff. I'll check around the water pump tonight and report back.
     
  5. ilovegirls

    ilovegirls Member

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    I thought of that but there's coolant spots on top of my reservoir. I'm going to check the water pump tonight as suggested by the above the post. Thanks!
     
  6. cnc97

    cnc97 Senior Member

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    The coolant spots on the reservoir are the result of combustion gasses over pressurizing the cooling system. It’s being forced out of the overflow.
     
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  7. ilovegirls

    ilovegirls Member

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    How does that happen? What causes this to occur and how do I fix this?

    I checked the water pump and no leak there. There is coolant on the motor mount.
     
  8. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    How many miles? Ever cleaned intake and Exhaust Gas Recirculation system?
     
  9. cnc97

    cnc97 Senior Member

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    When the head gasket fails, or is failing, the combustion gasses go into the oil passages or coolant passages. In the oil passages, it causes blow by, or can even blow the oil dipstick out. In the coolant passages, the gasses overcome the 16-18 lbs the cooling system is pressurized to. The overflow port is just below the cap on the reservoir. That would explain the coolant on the engine mount.
     
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  10. ilovegirls

    ilovegirls Member

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    205k miles

    EGR is clean along with intake manifold.
     
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  11. rjparker

    rjparker Senior Member

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    Are you ever getting a cold start knocking or rattle?
     
  12. ilovegirls

    ilovegirls Member

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    Nothing at all. Runs fine, no rough starts or rattles. Looks like a head gasket issue from the reply above and from Googling what causes pressure in the coolant system. I'll swap the motor and crank out another 200k on this car. Thanks all!!!
     
  13. ilovegirls

    ilovegirls Member

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    Thank you for the explanation.
     
  14. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Try a leak down test to determine if-and-where gasket is leaking. Eric the Car Guy has a video on the subject.
     
  15. ilovegirls

    ilovegirls Member

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    Ok. I'll look it up and give it a shot.
     
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  16. ChapmanF

    ChapmanF Senior Member

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    That particular video has come up before. I would suggest that it is not where you want to learn how to do a leakdown test.

    In this case, the problem doesn't seem to be Eric, but the particular leakdown tester he's using. I never see a name or logo in his video and if he named it I didn't catch it, but it looks a lot like what's in this other guy's video which is equally weird. That one is a "Pittsburgh" Harbor Freight brand, I guess this one. (Ok, now I see Eric's says "U.S. General" on the gauge dials.)

    Both Eric and this other guy have some mumbo-jumbo in their videos about "calibrating" the tester, and by the time they're done "calibrating", they've got the inlet regulator dialed back to something like 15 psi.

    weird.jpg

    So, the weird thing is that a leakdown tester is normally two matched pressure gauges on either side of a restricting orifice.

    [​IMG]

    [​IMG]

    What it really shows you (subtract the downstream gauge from the upstream) is the pressure drop across the orifice, which is a proxy for airflow rate into the cylinder. When the flow rate is zero (no leakage, never true in any real engine), the two gauges will read the same. You don't have to "calibrate" the input pressure, the leakage is zero whenever the two gauges match. It's just like measuring electric current with a shunt and a voltmeter, except the orifice pressure drop is more mathy than Ohm's law, so you'll usually just look up the gauge readings on a chart that comes with the instrument (see the lid of that OTC tester above).

    What this "U.S. General" or "Pittsburgh" tester is doing is just using a 15 psi fullscale gauge on the right, kind of camouflaged by changing its scale card to just read "0" at fullscale down to "100% leakage" on the left. And when you "calibrate" the thing, like its own manual tells you, of course you are setting the left gauge also no higher than 15 psi. They still use a 100 psi gauge on the left, but 85 of those pounds you'll never use.

    So ok, you will still be able to get some kind of a leakage reading with this. But when you try to then listen for where the leakage is going, it'll be a lot harder to hear than if you were using a more normal pressure.

    Eric even notices that in his video. He says "I don't know if this tester's a little weird or what but yeah it does say it's 100% leakage but I don't hear it going anywhere" and later even says "I'm not having faith in my tester because normally when I hook these things up and there's 100% leakage I hear it hissing and going somewhere."

    orwhat.jpg

    But he doesn't take the step back and ask "ok, what is it about this tester that's making it not useful that way?" That would have made it a more interesting video anyway.

    If you use a more traditional leakdown tester at a more traditional pressure ... you will hear where the air goes. :)

    Maybe there are a few reasons "U.S. General"/"Pittsburgh" made their tool to work at such a puny pressure?

    • Maybe so you can get away with using it on a smaller air source
    • Maybe so you can get away with forgetting to remove your radiator cap, oil fill cap, and dipstick before starting the test
    • Maybe so you can get away with forgetting to have a socket/breaker bar on the crankshaft blocked in place so the test won't spin it

    But seems like it just ends up being a less useful test.

    The little OTC tester shown above only seems to be $50 to $60 depending on where you look (and it seems to have a twin, the Proto JFP210M, identical but the plastic box is red). They are both obviously something repackaged from China, but at least it's two matched 100 psi gauges and will let you apply a more substantial test pressure.

    I don't know how much less the "U.S. General" / "Pittsburgh" thing is, but it doesn't seem like a bargain.

    I guess you could work with it though ... "calibrate" it to 15 psi first to judge your leakage rate, and if the rate is high, then crank the regulator higher and start listening for the sounds....
     
    #16 ChapmanF, Feb 27, 2021
    Last edited: Feb 27, 2021
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  17. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Eric get's it done in spite of the tester issues though. IIRC he determined it was leaking into the exhaust. There are some points of interest along the way, like how to determine TDC on compression stroke.
     
  18. ilovegirls

    ilovegirls Member

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    Thanks for clarification. Between the video and your explanation, the leak down test is something I'll have to learn how to do later. I made an appointment to do a leak down and currently looking for a motor swap.
     
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