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Karcher HD 3500 servicing


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07-25-15, 11:16 AM   #1  
Karcher HD 3500 servicing

There's a yellow cap and it reads motor oil 15w140 or 15wi 140.

What oil should I use in this pump?

It's at least 8 years old and behind a GX390 Honda, I think it's a tridex.

 
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07-25-15, 02:11 PM   #2  
The pump is a Triplex.

Most of the Karcher pressure washers call for the use of KARCHER 15W-40 Special Oil part number 6.288-050.0.

I don't know if standard motor oil will suffice.


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07-25-15, 02:47 PM   #3  
Ok, thanks. I did get in touch with a Karcher authorized service center today (surprising) and they said non-detergent oil also.

 
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07-25-15, 02:56 PM   #4  
Karcher HD3500 pump surging and leaking oil

I figured I would start a new thread on this issue...

The GX390 starts and runs perfect, but the pump is surging and builds pressure about every 3 seconds. I filled the pump halfway up the sight glass with 30W non-detergent pressure washer pump oil. The oil looks slightly aerated when running, is this normal?

Along with the surging, there is a leak where the arrow is. I did read about unloader valves causing issues and if so where would mine be located?

Does a gasket normally go here?

When it builds pressure it builds a lot of pressure, feels like I should but relaxes after it builds the pressure.

I picked it up used pretty cheap, maybe I can fix it still and not be out a ton of cash. I can return it still but maybe it's a cheap fix.

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07-25-15, 03:13 PM   #5  
Same thread is fine.

It does look like it's leaking at the seam. No gasket there but looks like there are seals.
The pump may have been allowed to freeze..... that would cause that to leak also.

ereplacement parts /karcher-3500-18109970-pressure-washer-parts-c-33388_33389_33638.html


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07-25-15, 04:27 PM   #6  
I pulled the pump and it looks like where the leak was, the nearest O-ring is almost flush with the housing, if not very slightly recessed.

Would freezing create a crack somewhere or just mess up the O-rings?

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07-25-15, 05:21 PM   #7  
Based on the parts diagram, could someone point me to the unloader valve? I'm at a loss as to it's location.

 
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07-25-15, 06:12 PM   #8  
I also need the torqe value for the 4 allen head pump bolts for the main unit to the middle unit, not the pump to engine....and the torque value for the 5 allen head bolts at the front of the pump if possible.....thanks.

 
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07-26-15, 07:47 AM   #9  
Here's a quick vid on the surging.


https://www.youtube.com/watch?v=MSUIKOaO0cc

 
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07-26-15, 08:14 AM   #10  
Have you checked the water flow to the pump, doesn't seem like it is getting enough water. Have a good one. Geo

 
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07-26-15, 11:01 AM   #11  
I did verify the flow, I have just over 6GPM at the end of the hose at the pump inlet.

If I turn the pressure control knob down to where it's just starting to increase pressure from the minimum setting, it will stay there, but just a slight turn out and it starts cycling.

 
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07-27-15, 08:07 PM   #12  
It appears the unloader is behind the pressure adjustment knob, I removed it and it looked good but lubed it anyway...still same surging.

I may be able to just replace the unloader, and the leaking O-ring and some fresh seals. I have been looking at the AR Cat General Comet RRV4G40 pump, may just bite the bullet and get a fresh pump. This one appears to have good reviews especially for the price...any thoughts?

 
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08-08-15, 10:03 AM   #13  
I replaced the pump with the AR RRV4G40 pump. Works great. I verified pressure and it's putting out 3300 PSI, is this normal for a 4000 PSI pump? I understand it's advertised to operate at 3600 PSI but I assume there are many variables.


Onto the hose reel.....what can I use to get this fitting at 45 deg so I can use a hose through the slotted opening? Would iron pipe work?

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