1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Strange PSI issue

Discussion in 'Gen 4 Prius Main Forum' started by unigeezer, Feb 23, 2024.

  1. unigeezer

    unigeezer Member

    Joined:
    Jul 7, 2008
    216
    58
    0
    Location:
    torrance, ca
    Vehicle:
    2011 Prius
    Model:
    Three
    I'm a little bit baffled. I noticed my driver side front tire has been losing almost exactly 10 psi when I check it every morning. I've removed the wheel, dunked it in water, used soapy spray on the tread, the bead seal on both sides, and the valve stem and could find no evidence of a leak. Not a single solitary bubble. I usually run 42 PSI in the front and 40 in the back but every morning when I check it it has dropped roughly 10 psi down to 32 psi. It just seems to stop at that point and does not lose any further pressure. Any thoughts on why this is happening?
     
  2. jdenenberg

    jdenenberg EE Professor

    Joined:
    Nov 21, 2005
    3,837
    1,827
    1
    Location:
    Trumbull, CT
    Vehicle:
    2020 Prius
    Model:
    LE AWD-e
    Are you pumping the tire back up to 42 psi before testing for a leak? Check that the valve in the valve stem is tightly screwed in.

    JeffD
     
  3. unigeezer

    unigeezer Member

    Joined:
    Jul 7, 2008
    216
    58
    0
    Location:
    torrance, ca
    Vehicle:
    2011 Prius
    Model:
    Three
    Sorry, I forgot to clarify. Yes, I inflate back to 42 psi before checking for leaks. I also checked the valve stem and it felt tight. But I went ahead and backed it of a bit and re-tightened. Now, with the electric pump still attached to the valve after inflating, it's not losing pressure.
     
    #3 unigeezer, Feb 23, 2024
    Last edited: Feb 23, 2024
  4. AzWxGuy

    AzWxGuy Weather Guy

    Joined:
    May 22, 2011
    967
    489
    0
    Location:
    Tucson, AZ
    Vehicle:
    2021 Prius
    Model:
    Limited
    Anybody gaslighting you? There are earlier threads about people messing with fuel tank levels for the entertainment value in that. Are you confident there is no tire damage? Maybe time for a professional inspection?
     
  5. unigeezer

    unigeezer Member

    Joined:
    Jul 7, 2008
    216
    58
    0
    Location:
    torrance, ca
    Vehicle:
    2011 Prius
    Model:
    Three
    I had used an external plug about 6 months ago after finding a nail in the tread. The repair was successful and there wasn't an issue until just recently so my assumption is that the plug was starting to fail even though I couldn't confirm using soap and water. But after thoroughly inspecting the tire, the bead seal on both sides and the valve and not finding any evidence of leaks there, I assumed the plug was the culprit. I have since ordered a replacement tire.
     
  6. trailblazer55

    trailblazer55 New Member

    Joined:
    Nov 6, 2023
    3
    0
    0
    Location:
    Miami, FL
    Vehicle:
    2020 Prius
    Model:
    Four
    I believe plugging your tire is only a temporary fix until you get a replacement tire. 6 months is a good amount of time that it held up! Hate dealing with nails...
     
  7. sylvaing

    sylvaing Active Member

    Joined:
    Jul 15, 2023
    845
    357
    0
    Location:
    Canada
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Base
    Sorry to hijack but... what???
     
  8. vvillovv

    vvillovv Senior Member

    Joined:
    Mar 19, 2013
    3,525
    1,241
    1
    Location:
    NY
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Pull an all nighter when you have a day off and check pressure every hour or two. If you don't have a second gauge and only use your electric pump gauge, get and test a second tire pressure gauge. Some gauges work better than others.
    Can you still locate / see the plug you installed 6 months ago?
     
  9. unigeezer

    unigeezer Member

    Joined:
    Jul 7, 2008
    216
    58
    0
    Location:
    torrance, ca
    Vehicle:
    2011 Prius
    Model:
    Three
    Yes, the plug is visible, and seemed to still be holding as I could not see bubbles forming using soap/water with full weight of car and at 40 psi. I ended up replacing the tire.
     
    Doug McC and vvillovv like this.
  10. AzWxGuy

    AzWxGuy Weather Guy

    Joined:
    May 22, 2011
    967
    489
    0
    Location:
    Tucson, AZ
    Vehicle:
    2021 Prius
    Model:
    Limited
    It was in one of the earlier generation sub-forums, thinking Gen II. Some guys at work messing with their friend who was all about his amazing fuel economy. Somehow those guys were adding fuel to the tank (locked fuel door?) for a couple of weeks and then subtracting fuel in the same manner. Then chuckling to themselves when the story is told.
     
    sylvaing likes this.
  11. unigeezer

    unigeezer Member

    Joined:
    Jul 7, 2008
    216
    58
    0
    Location:
    torrance, ca
    Vehicle:
    2011 Prius
    Model:
    Three
    On a related note, what would be the recommended PSI that would create the best balance between optimum MPG and longest tread life?
     
  12. Brian1954

    Brian1954 Active Member

    Joined:
    Jan 31, 2021
    649
    245
    0
    Location:
    South Central PA, USA
    Vehicle:
    2011 Prius
    Model:
    III
    You will get a lot of different recommendations for tire air pressure from members on this forum. Personally, I inflated my tires to 2 PSI higher than what Toyota recommends on the label at the drivers door.
     
    vvillovv likes this.