Coolant leak at reservoir

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Djh650, Jan 10, 2026 at 3:29 PM.

  1. Djh650

    Djh650 New Member

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    Hello, first time poster. Very new to prius. Picked up a 2015 plug in with 236k. Had the dreaded misfire on cylinder 2 on start up. Started with the easier fixes first...cleaned EGR & replaced spark plugs. During this maintenance, I had to wait a few days in-between disassembly & reassembly (rain, cold ) i had the radiator hoses clamped off, but I still lost a ton of fluid (I'm assuming due to temp change pressure).

    I refilled coolant levels back up, on first start up, no more misfire, but I heard a liquid sloshing sound. Researched and found out it may be due to air in the system. Followed the procedure to put the car into maintenance mode. While waiting for the fan to turn on, coolant started leaking from below the reservoir.

    What are my next steps? I have a good amount of tools, but very new to prius.
     
    #1 Djh650, Jan 10, 2026 at 3:29 PM
  2. bisco

    bisco cookie crumbler

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    see if it is the hose or the reservoir. if it is the reservoir, maybe you can find one on ebay or salvage
     
    #2 bisco, Jan 11, 2026 at 3:17 PM
    Brian1954 likes this.
  3. Brian1954

    Brian1954 Senior Member

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    My guess is that the coolant is escaping from the little pressure release nipple just to the rear side of the cap on the reservoir. If that is where the coolant is coming from, then your engine is overheating due to a bad engine coolant pump. Use a scanner to monitor the engine coolant temperature.

    If the engine is overheating due to a bad pump, the engine probably also has a bad head gasket.
     
    #3 Brian1954, Jan 11, 2026 at 7:44 PM
    Last edited: Jan 11, 2026 at 8:41 PM
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  4. Mendel Leisk

    Mendel Leisk MMX GEN III

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    There should be more publicity about these: most any gen 3 for sale these days is being ditched, with untouched EGR, blown head gasket, and stop-leak product gumming up the coolant system. What sort of seller, how much was it?
     
    #4 Mendel Leisk, Jan 12, 2026 at 8:43 AM
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