Any pressure cleaner wizards?

Sep 22, 2011 4 Replies
G

I have a 5hp electric pressure washer that uses a CAT 3DX pump. The pressure has been falling off and now is at a point that it is virtually unusable. The input filter is clean, I took the unloader apart and things look OK in there. I am now left with the pump itself I think. I pulled it apart (the 8 allens and the 3 caps). The pistons look OK, looking in the holes, I don't see anything obvious with the check valves, no broken springs, no contamination. I can see all the way through all the passages and they are open. I think I am down to ordering a rebuild kit but by the time I get a seal kit ($90) and a check valve kit ($164) I am 85% into the price of a hole new pump assembly with everything attached.



This is a $700 pressure washer, the pump is $300 and the kits are $254 plus shipping.



At this point I am about to start pumping WD40 or some other solvent through it to see if that doesn't free something up. I don't see I have much to lose since tossing the pump is the next step.



I would really enjoy hearing something better since I have another CAT



4 piston pump on the shelf that is bad the same way and a little electric pressure washer that doesn't work that well either.

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G

Thanks but that was the first thing we did.

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R

I am no expert but i have rebuilt many of those style piston pump=20 heads for a spray car wash business.

Similar symptoms as you describe. The sprayers would go from great to=20 suddenly loosing pressure. After another week of use the sprayer=20 would be practically useless.

90% of the time a rebuild of the pump head would fix it. Some times=20 the metal check valves at the top of the piston would be the culprit=20 other time the cups or seals in the piston itself would be the=20 problem. Eventually we would just rebuilt the whole top. Most times=20 there would appear to be nothing obviously worn on the parts so even=20 the smallest amount of wear must cause the trouble. I did notice over=20 time that the metal check valve cups would appear polished where the=20 new ones had a dull faced flat finish.

If your sprayer is well used then it could very well be the piston or=20 check valve assembly. If it has been accidentally run dry on occasion that will speed up the=20 demise.

Occasionally, when our stock of pump rebuild parts was depleted i=20 experimented with trying to refinish the metal check valve cups and=20 their seats by honing or lapping with various fine finish files ,=20 stones and emery cloth to get a pump working again for a while. I=20 would essentially take the metal cup and hone or lapp against a known=20 flat surface and try to get the finish to the similar satin finish the=20 new ones would have. Doing this made it obvious that the polished wear=20 rings were actually uneven , and deeper than apparent to the naked=20 eye. I suppose if the valve turns a bit the uneven wear will cause=20 them to tilt and zap the pressure.

anyways I hope this helps.

robb

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G

Thanks Robb. That is what I was believing myself. We have used this a lot and our water really sucks. I am going to try the WD40 thing, just to be sure it isn't just gummed up somewhere but I think a new pump is how I am going to go. The parts are almost as much as a pump.

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G

OK I did the WD40 trick. I attached a hose to the intake and one to the output, and cycled about a pint of WD40 through there until it got up to about 110 degrees, (can getting hot in my hand, a minute or so). I turned it off, hooked it up and I got 2600 pounds when the unloader popped off and about 2100 with a 15 degree nozzle on it. I can live with that.

One more thing WD40 can do for you.

I still think a pump is in my future but not right now.

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