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Repair Parts Home  Lawn Equipment Parts  Karcher Parts  4.591-040.0 Unloader Valve

Unloader Valve

Part Number: 4.591-040.0
Karcher
Availability: 25+ in stock
Price: $16.91
Quantity:
Ships within 1 business day

*This part replaces obsolete part #: and 4.591-036.0.

Description:
This is a genuine Karcher replacement part, it is sold individually.
When your pressure washer loses pressure, it probably means you have a bad spill valve.
Also known as an unloader valve.
This part allows water to recirculate in the pump when you're not spraying water and is responsible for most of the pressure-related problems with your pressure washer.

We do have an article and video on "How to Replace the Spill Valve on a Karcher Pressure Washer" on our site. Just go to the front page of our site and click on Repair Center.

Product Information
Manufacturer: Karcher
Product Number: 4.591-040.0
Classification: Part
Weight: 0.02 lbs.
Also Known As: Spill Valve, Unloader
Shipping: Ships Worldwide
Products Compatibility

This item works with the following types of products:

  • • Pressure Washer
Questions & Answers

the power washer leaks from the area the black sleeve by the unloader valve.. and it runs rough with more water leaking when it is not actively pumping.. should i replace the valve?
Brian for model number 240hh
Hello Brian, Thank you for the question. Yes, the first place to start would be replacing the Unloader Valve. Thank you for your inquiry, good luck with this repair!
What type of oil goes into the pump?
Lou for model number G2600VH
Hello Lou, thank you for inquiring. The Pump Oil for your model is part 6.288-050.0 on our website. It is synthetic 15W40 oil. We hope this helps.
Why does my pressure washer motor keep running after the wand is released?. it is working fine otherwise.
sam for model number karcher 1800
Hi Sam, thank you for your question. You may want to check your valve and try to determine if perhaps it is stuck in an open position. I hope that helps. Good luck with your repair.
Replaced the unloader value but the pressure still pauses. Any help would be appreciated. Thanks Chuck
Chuck for model number Karcher 2400 pressure washer
Hi Chuck, Thank you for your question. If you have already replaced the unloader valve and you are still not getting any pressure, there are some other parts that you will need to check to see which ones are causing the issue. You will need to check the pressure spring, the pressure check valve set, the pump check valve and the pump oil. I hope this helps. Thank you and have a great day!
Engine doesn't speed up when the handle is pulled?
Casey for model number K2300g
Hello Casey, thank you for your question. We would recommend replacing the Unloaded Valve Part # 4.591-040.0 and the Pressure Check Valve Set Part # 2.884-916.0. I hope this helps!
Repair Instructions: Submitted by Customers Like You
70 of 71 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Easy
Time Spent Repairing:
30-60 minutes
Tools Used:
Screwdriver, Pliers, Allen wrench
High pressure intermittent on Karcher 2401 HH pressure washer.
After pulling the pump off, I first tried pulling the spill valve with needle nose pliers. It was in there to tight to pull out so I reinstalled the pump without the cover on the spill valve. Hook the hoses up to the pressure washer as you normally would and turn on the water. The spill valve did not push out, so I started the engine and "pop" - slick as a whistle the valve came out. Next time I'll just leave the pump in place and take the the cover off the valve and pop out the valve as I just described. Reassemble just as the eReplacement Parts video shows. A note: The spill valve part # 4.591-040 actually is a direct replacement for 4.591-036, so fear not. It looks like they improved the upper o-ring grove so the o-ring fits better without the need for a spacer. Otherwise the dimensions are identical.
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50 of 50 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Easy
Time Spent Repairing:
15-30 minutes
Tools Used:
Socket set, long nose vise grips
Karcher 2400 pressure washer wouldn't pressure-up when trigger was pulled - bad unloader valve
Had to remove the pump from the motor due to not enough clearance between the unloader valve and the frame above it to access the old unloader valve. This was just 4 bolts, very easy. The toughest part of this repair was extracting the old unloader valve from the pump. Long nose pliers were nowhere near enough, they would just slip off no matter how tightly they were gripped. The tool that solved this problem was a pair of long nose vise grips. They were able to firmly clamp on the top of the old valve and pull it out. Having this tool was *essential* for completing this repair. (Other brands of pressure washer may not present this difficulty in removing the old valve) Applied a little Teflon grease on the top O-ring of the new valve and reassembled the pump. Works like new now!
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11 of 14 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Easy
Time Spent Repairing:
Less than 15 minutes
Tools Used:
Pliers, Socket set, allen key
Pump goes into bypass and doesn't pressure up.
I followed the video on you tube. Thank you.

https://www.youtube.com/watch?v=SAhiUyk3TIk
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6 of 7 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Medium
Time Spent Repairing:
More than 2 hours
Tools Used:
Screwdriver, Pliers, Power Drill, Socket set, Wrench Set
No pressure
Tried every pair of pliers and vice grips available could not get the valve out.
I ended up having to drill and tap the valve with 10-32 threads. I put in a socket head screw and still couldn't get it out with the vice grips. I finally was able to pry it out by using two screwdrivers under the screw head. The valve cavity was very corroded so I wrapped fine sandpaper around a small drill bit and used my drill to clean it up a little. Installed the new valve and it works fine now.
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5 of 5 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Easy
Time Spent Repairing:
15-30 minutes
Tools Used:
Pliers, Socket set, Wrench Set, Torx #30 driver
Washer lost high pressure
1. Spent part of a day becoming an expert on karcher washer pumps (u-tube, karcher, et. al.)
2. Removed washer front cover.
3. Removed unloader cover with screwdriver.
4. Removed plastic unloader cap screws with torx driver.
5. Removed top spring & seals.
6. Removed broken unloader (spill) valve.
7. Reassembled top spring & seals & new spill valve after lubing seal surfaces with lithium grease.
8. Notes: Clean off any corrosion; no grease on spill valve lower seal surface.
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4 of 5 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Easy
Time Spent Repairing:
30-60 minutes
Tools Used:
Screwdriver, Pliers, Nutdriver, Adjustable Wrench, Allen
No Pressure when handle pressed
Followed your tube tube video and fixed problem by replacing bent valve.
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2 of 2 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Medium
Time Spent Repairing:
1-2 hours
Tools Used:
Screwdriver, Allen wrench, torx screwdriver & large needle-nose pliers.
Unloader valve failed
Placed Karcher pressure washer on truck tailgate.
Used allen wrench to loosen 4 bolts holding pump onto the pressure washer motor.
Removed button cap holding black cap on to the pump.
Used torx screwdriver to remove 2 screws on white plastic upper portion piece that houses the unloader valve.
Removed spring, then used large needle-nose pliers to remove unloader valve.
Put grease around green band on new unloader valve.
Reinserted the new unloader valve into the pump.
Put spring and white plastic piece back in place and screwed into place.
Put black cap and button cap back into place.
Reinstalled pump back onto the pressure washer and tightened all 4 bolts.
Hooked up water hose and turned on spigot.
Started the pressure washer and all worked fine.
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3 of 4 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Medium
Time Spent Repairing:
1-2 hours
Tools Used:
Screwdriver, Pliers, Socket set, Wrench Set
SPRAY WAS PULSING -
Had broken internal valve which was replaced. Your repair video was very helpful. As a precaution I replaced all 6 valves instead of just the one that broke. Spill valve was also replaced. Works fine now.
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1 of 1 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Medium
Time Spent Repairing:
30-60 minutes
Tools Used:
Screwdriver, Pliers, Socket set, Wrench Set, Nutdriver, Rubber mallet, needle nose vise grips
Spill valve was sticking so the pressure washer would surge or stop working.
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1 of 1 people found this instruction helpful
Tool Type:
Pressure Washer
Parts Used:
Unloader Valve - 4.591-040.0
Repair Difficulty:
Hard
Time Spent Repairing:
More than 2 hours
Tools Used:
Pliers, Socket set, Nutdriver
no pressure
I watched your video on pump repair several times before starting. Pulled pump, disassembled per video instruction. Found 3 stuck valves (pistons caught in the springs... unstuck them and put them back. Replaced unloader valve. Reassembled pump per video instruction. Remounted pump per video instruction. To my utter amazement, it worked like a charm!

I did all this with the instruction from the video. Could not have done it without the video, I am a scientist and not mechanically inclined

B.G. Huff
Philo, IL
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  • worked as expected
    fast delivery, easy to order. Great company
    Guest - 11 days ago Verified Purchase
    Valve was the exact part needed.
    Probably could have gotten the part other places, but your site was great in helping me determine what part to get and how to replace it. Great and informative help. Thanks
    Guest - 22 days ago Verified Purchase
    Easy Repair, but...
    The part is a Karcher part and works as advertised. BUT, this part seems to have a short life expectancy. One of the videos on the eReplacement site briefly alludes to this fact. It would be nice if Karcher came up with a better part. So, my advice is to order two - one for repair and one for the next repair.
    Jim - April 24, 2019 Verified Purchase
    Solved my problem
    Part arrived on time and in good condition. My Karcher power washer is now working again. Thank you.
    Guest - April 18, 2019 Verified Purchase
    Verified Purchase
    eReplacementParts Team
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