Just cleaned EGR and Manifold on my 2010

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by LazuliNyx, Nov 1, 2024.

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  1. LazuliNyx

    LazuliNyx New Member

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    I just did a cleaning on my EGR valve/cooler and intake manifold (and planning to install an oil catch can). I was getting an intermittent P0401. I haven’t driven it enough to know if it will turn, but is there a way to test EGR flow to make sure it’s normal? I’ve done some searching and haven’t found a way to do it using an OBD-II adapter and apps on my phone such as OBD Fusion. Thank you!
     
  2. Mendel Leisk

    Mendel Leisk Witness Leader

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    What's the miles?
     
  3. LazuliNyx

    LazuliNyx New Member

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  4. Brian1954

    Brian1954 Senior Member

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    Read posts #1, #6, #40, and more in this long thread:https://priuschat.com/index.php?posts/2884348
     
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  5. Mendel Leisk

    Mendel Leisk Witness Leader

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    Don't be surprised if the "other thing" comes along soon (head gasket failure). My 2 cents:

    The engine's wellbeing depends on the EGR system behaving as it was when it rolled out of the factory. Judging from the rate it accumulates carbon, and considering how onerous the cleaning is, I'd recommend every 50K miles.

    At 171K miles, the engine's been running for a protracted time with insufficiently cooled exhaust gas, reduced flow, possible damaged EGR valve, and last but not least: an asymmetrical reduction in EGR gas supply, with the cylinder one end being the most clogged.

    Is coolant level stable in the reservoir?
    Have you had engine shaking on cold starts, particularly after sitting overnight?
     
    #5 Mendel Leisk, Nov 2, 2024
    Last edited: Nov 2, 2024
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  6. burebista

    burebista Active Member

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    Readme. :)
     
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  7. LazuliNyx

    LazuliNyx New Member

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    I've had it since about 120K, so I don't know if the previous owner had the EGR cleaned, but I'm going to bet it wasn't done. Sometimes the engine does shake when coming on during driving, but it's not consistent. I need to top off the coolant and watch it, since I lost some doing the EGR clean. Any other symptoms to look out for? the oil getting into the engine appeared to be via the PCV valve, hence why I'm planning to add an OCC. Does anything help with the carbon buildups in the EGR system? Cleaning it regularly wouldn't be so bad if it wasn't for all the work to get access to it.

    Thanks!
     
  8. Mendel Leisk

    Mendel Leisk Witness Leader

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    Yeah I don't think Toyota saw this coming, and now it seems like they just want all the customers to "go away". Not atypical for car companies now.

    Mercifully it's possible to get the EGR components out, and there are a few tricks. For sure take the wipers and cowl off; heck you have to do that for just the spark plugs. A couple more tips:

    1. Remove the EGR cooler lower nut, at least. And leave it off permanently. Better: remove the stud there too, because then you can extract the cooler without removing the two rearmost studs, at the exhaust manifold connection. Side benefit: the gasket at the exhaust mainifold will hang up on those studs, not drop down, never to been again. And when reinstalling the studs will retain/align the gasket. Note: that lower cooler bracket stud will likely be very stubborn; it took me at least 15 stressful minutes backing it out, one click at a time with a dimnutive 1/4" wrench, one-click at a time (due to all the adjacent stuff), fearing I was going to round it off.

    2. To avoid virtually all coolant spillage, before doing anything drain 2 quarts or liters of coolant from the radiator drain. This will drop the level below the EGR system, apart from a little trapped at the back corner of the cooler. When everything is done just pour it back into the reservoir. With a 2010 you'll have the engine coolant vent (white cap on black plastic coolant junction, just above EGR components). Leave it open while pouring the coolant back in, and squeeze the coolant hoses as you go. When coolant starts coming out of the vent close it. Coolant will end up slightly higer in reservoir, will settle down with a few days drving.

    More details, info, links in top two links in my signature. On a phone turn it landscape to see signatures.

    All that said, there's still a risk the head gasket is going to let go soon, or it's started; boroscope inspection of the interior of the four cylinders can help diagnose that.

    For the P0401, maybe the EGR valve has sustained damage. The EGR cooler (colloquial name, Toyota calls it "Pipe) name is called cooler for a reason: it's interanal radiator is supposed to cool the exahust gas passing through. Carbon coating acts like an insulator, reducing it's efficacy. Just downstream is the EGR valve, which contains an inverted plastic bucket with a small ramp and stop. This latter can develop a groove, perhaps from overheating, and then not function properly. With flow reduced by carbon build up the valve may also be going through more up/down travel, to compensate? Anway, deffective valve might be the cause of the code.
     
    #8 Mendel Leisk, Nov 3, 2024
    Last edited: Nov 3, 2024
  9. LazuliNyx

    LazuliNyx New Member

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    Good to know! Yeah I observed those things when I took it apart. I did not see any physical damage on the EGR valve including on the actuator side that turns the valve open, but one can never be sure. If the P0401 goes away hopefully all will be good with the system, but that head gasket worries me. That’s good advice with draining the coolant. Ironically, I lost a bolt stud pulling the cooler off. Good to know it’s ok with one bolt. I’ve had experience fixing cars of all makes and I know I could figure out how to do a head gasket, though with my disability I’ll probably need help from my partner.
     
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  10. rjparker

    rjparker Tu Humilde Sirviente

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    A 401 can be caused by flow at low rpm’s when the egr valve is shut, by egr pipe leaks or by a complete egr cooler clog. The car is automatically testing for those conditions which creates the code.

    The Techstream egr step test described in the links above makes it easy to determine if your 401 is a sticking valve or a clogged egr system.

    Toyota knew they had various engine problems and released several revised parts and updated ecm code. One was a revised egr valve.
     
  11. Mendel Leisk

    Mendel Leisk Witness Leader

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    OP reports everything was cleaned though.
     
  12. rjparker

    rjparker Tu Humilde Sirviente

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    Clean does nothing for sticking valves or leaks.
     
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  13. RightOnTime

    RightOnTime Senior Member

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    Very important! Did you check the waterpump for any type of tension from impeller?