Question about Karcher 2500 PSI Pressure Washer

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  • XYLOMAN May 09, 2008

    no that is not the problem.i start the pump i get the pressure, when i let the trigger go i can only get the pressure back if i remove the tip let the water run, put the tip back on again and pull the trigger, so what is going on is the pomp pulling in air?

  • XYLOMAN May 10, 2008

    thanks very much for the help i know i can do the job one problem i do not have the parts manual can you direct me on that?

  • XYLOMAN May 10, 2008

    To IrishDruid,

    I want to thank you very much for your help. I got my Karcher working and it's performing beautifully. Thank you!

  • Anonymous Mar 15, 2014

    How do I install a replacement pull cord for a Honda Pressure Washer engine Gc 160 ?


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Hi - You're not trying to use the gun safety lock to keep the trigger on are you? I know how it sounds but I have to ask. This feature is just meant to act as a safety so that the trigger can not be accidentaly engaged. You are supposed to lose pressure when you let go of the trigger.

Posted on May 09, 2008

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Hello Xyloman,

Unfortunately, this is a common problem with the Karcher..

The problem is most likely the bypass/unloader valve that gets stuck with corrosion in the pump valve body and prevents or hinders the pressure from changing from low to high pressure. You can try to remove and lube the bypass valve but the fix won't last for long.


A better option would be to replace the upper O-ring with another of similar thickness, but half the diameter. You should be able to purchase these from a hardware or scuba equipment store..
To get at the unloader you need to remove the unloader cover. Unscrew the loader top portion (off white typically), a copper looking plunger and spring will be present (THIS IS NOT THE UNLOADER). Then placing a rag over the opening apply water (if the unloader doesn't pop out, start the engine briefly and it should. Remove the upper O-ring (the larger one) but do not alter the split ring(this one is plastic). Replace with new smaller O-ring and replace, this should fix the problem. The idea is that the original stuck out from the valve about a 1mm but this make the valve stick, the new O-ring should be almost exactly flush.


The following is an easy 5-minute fix. You will need a #30 Torx, a straight slot screwdriver and a tube of white lithium grease.

1. With a screwdriver, pry off the silver button (#1) from the black plastic cover (#2).
2. Remove the black plastic cover (#2) from the pump.
3. With a #30 Torx or a Phillips driver, remove the two screws that hold the thermo valve housing (#3) to the pump.
The clearance is limited and you may need a right-angled driver or a bit driven with a wrench at aright angle to the screw.
4. Remove the thermo valve housing (#3), the thermo valve (#5), and the thermo valve spring (#6) from the pump.
5. Connect your garden hose to the input of the pump.
6. Connect the hose, gun and wand to the high-pressure outlet of the pump.
7. Turn on the water to the garden hose. The pressure should force the unloader (#8) out of the pump.
8. If this does not work, start the pump and stand back.
9. Turn off the water (and pump) and find where the unloader (#8) landed.
10. Lightly lube the o-rings at the top and bottom of the unloader with either white lithium or silicon grease.
11. Reassemble the unloader in the reverse order given above.

Hope that helps!


Posted on May 09, 2008

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  • Swilin Sampson
    Swilin Sampson May 09, 2008

    If lubricating with lithium grease the unloader
    valve does not work, I would suggest replacing it all together. The part can be purchased at, call 800 899 2245, Item # 4591040
    called a "Spill Valve Complete". It costs about $19 plus shipping plus
    shipping and fully refundable if it does not work. Pretty easy fix for
    a low cost.

    And BTW, if you are losing pressure just because you are releasing the trigger and nothing else, then there is no need to worry. The pressure stays high as long as the trigger is pressed, and releasing the trigger will release the pressure. That is the way it is supposed to work...

  • Swilin Sampson
    Swilin Sampson May 09, 2008

    It is most likely the unloader valve. Also ensure that the pressure hose is laid out straight and not kinked. Another thing is to make sure that the water faucet is fully on.

  • Swilin Sampson
    Swilin Sampson May 10, 2008

    Unfortunately, Honda does not publish a parts manual for this product. However, should I come across it, I will post it here. However, its not too difficult to do. Once you find the silver button, you should be able to get to the unloader valve pretty easily.

  • Swilin Sampson
    Swilin Sampson May 10, 2008

    Ok, HERE is a user manual. (It should be under "Gas Mosels" on the right side). You should have Adobe Acrobat to view this file.
    You can view the parts manual HERE. (You should find it listed on the left side under"Gas Models")

    Hope that helps!

  • Swilin Sampson
    Swilin Sampson May 10, 2008

    You are most welcome! It was my pleasure.
    Now if you would be kind as to assign a Fixya rating to my solution, I would be most grateful :)


  • Swilin Sampson
    Swilin Sampson May 12, 2008

    Just wanted to remind you that you have forgotten to assign a FIXYA rating for my solution. Please take a minute to do so..


  • Swilin Sampson
    Swilin Sampson May 18, 2008

    Hello, please select "Accept" under my solution so that you can credit me with the resolution of this issue...Thanks.


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Hello there.

If the washer is loosing pressure then it needs to be looked at under warranty, im not sure where the fault would be, but another expert may well know.

If you don't get any suggestions then i would take it back and ask for a replacement or repair.

Hope this helps.

Posted on May 09, 2008

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