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Old 10-27-2020, 01:42 PM   #1
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Shurflo 4048 water pump stripped screw threads

My Pentair Shurflo 4048 water pump stopped working and started leaking when the 4 corner screws came loose and a couple of the 4 inner screws came loose. See the exploded diagram below. All the screws are #10-32.

I tightened the screws and got by for the rest of my trip, but the screws started to come loose again, so I disassembled the pump to see what was going on. I found that the pump comes with a bizarre approach to the housing screws that is simultaneously flimsy and overbuilt.

The 4 corner screws only go a short distance into the motor housing, even though there is room for a longer threaded screw. I tapped it out and put in longer screws, but my problem now is that the loose operation stripped the top left screw in the housing. I put on Loctite blue to hold it, and it came loose. I put in more Loctite blue along more thread length, and I'll see what happens. But, I suspect it will fail. I have 3 choices for the repair and would be interested in the experience of others with this problem:
1. Drill out the hole and thread it with a #12-32 screw and Loctite Blue. Hopefully there is enough room that I don't damage any other parts like the diaphragm.
2. Use Loctite Red or Green. That will hold, but will be impossible to undo unless I heat it. Heat would damage the plastic housing and diaphragm. That gets expensive.
3. Install some sort of backer on the pump housing to allow for a nut on a longer screw, or glue in a backer to allow for the hole to be extended and more threads to be cut for a longer screw.

Have people encountered this and how did they approach the problem?

The problem arises because Shurflo only lets the screw bite on about 1/8" of thread. That's OK if it is a hardened nut, but not enough for the cast housing.

It looks like Shurflo has dealt with a similar problem with the 4 inner screws, which go into backing plate to sandwich the rubber diaphragm. When these screws loosen, the whole pump leaks water. And, those screws also only go into about 1/8" of metal. Shurflo recognized the problem of these going loose and sealed the threads in with something equivalent to Loctite Red. When I tried to remove these screws, it was very hard (for the ones that hadn't loosened themselves). I ultimately wound up twisting three of the screws and breaking the other. Fortunately, these are the same screws as the 4 corner ones, so I used those in order to get the precisely correct screw length.

Shurflo didn't do a careful job of designing the pump. Allowing for longer threads would have been a simple fix.

–Gordon
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Old 10-27-2020, 01:56 PM   #2
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If this is the original pump, then it worked for about 6 years before failing?
Every unit I have owned had a Shurflo water pump. I've never run into this problem, but I can see how it would happen. They all vibrate tremendously! I usually put mine on a rubber pad that dampens vibration and noise.
I admire your efforts to fix the problem with longer screws and backer plates, but I think you will be fighting a losing battle.
Perhaps it's time to look at replacing it, maybe with a different high flow model. Or perhaps Shurflo has redesigned this model in the mean time.
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Old 10-27-2020, 03:27 PM   #3
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I'd say it's time to replace the old pump. The newer SHURflo 4008 & 4048 Revolution Pumps have corner screws that go all the way through the aluminum mounting flange.
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Old 10-27-2020, 03:43 PM   #4
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I replaced mine 3 years ago with a REMCO water pump with 5.3 gpm capability. Really happy with it!
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Old 10-28-2020, 01:53 PM   #5
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Use this

Fix the stripped thread with one of these. The original brand was Helicoil, but the generic ones are much less expensive. Also available at your local auto parts store.

It surprises me that Shurflo engineers used 10-32 NF machine screws into cast metal. Best practice is to use coarse (e.g., 10-24 NC) threads into cast metal because the fine threads in the grainy casting are easily stripped.

National Coarse (NC) for castings like iron and zinc
National Fine (NF) for malleable metals like steel and brass
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Old 10-28-2020, 05:39 PM   #6
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Larry,
I agree that NC would have been the proper choice of screw thread for the pump. The Helicoil idea looks good. I assume that I have to drill the hole out a bit to make room for it. I guess an alternative would be to wrap some thin wire (or a coil spring) around the screw threads and screw it back in, along with some Loctite.

DW,
I do have the latest model of Shurflo 4048 pump, which is the 4048-153-A75 item in their catalog https://www.pentair.com/content/dam/...rv-catalog.pdf
The catalog picture you have shows the screw going slightly beyond the end of the housing. My screw was likely 1/16" or even 1/8" shorter. It didn't come through the housing. It was about 1/16" short of the end. But, the extra 1/16" of an inch probably wouldn't have been enough. Maybe I had a bad model run.

NMWildcat,
I agree that this is an unusually short life for a water pump. My old trailer had a pump that looked the same (same prefilter, etc), and it was going strong after 20 years.

Edgewant,
The Remco pump could be better. It is rated at 5.3 gallons per minute and the 4048 Pentair is listed at 4 GPM. But, I don't have a problem with low flow. I'd be interested in seeing some reviews and tests of Remco vs Shurflo before investing in a new pump. That makes me inclined to repair my Shurflo, since this seems to be the only flaw in its design, so far.

I've got my coach in storage for the winter, so I won't be able to do the fix until the spring. I was interested in ideas on how to approach the problem when spring does roll around.

–Gordon
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Old 10-28-2020, 06:12 PM   #7
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$60 bucks on Ebay incl shipping!
Good luck!
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Old 10-28-2020, 06:21 PM   #8
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My Shurflo pump is really hard to get to. Only can use one hand and reaching real far. I have short arms. I remounted it a couple years ago quieted it down. this year noticed it was getting noisy again. I used zip ties around base and pump when winterizing. Must be the screws from the base to the pump coming loose. It quieted down again.
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Old 10-28-2020, 07:46 PM   #9
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Quote:
Originally Posted by gordonsick View Post
Larry,
I agree that NC would have been the proper choice of screw thread for the pump. The Helicoil idea looks good. I assume that I have to drill the hole out a bit to make room for it. I guess an alternative would be to wrap some thin wire (or a coil spring) around the screw threads and screw it back in, along with some Loctite.
Gordon,

If you have never used helicoils, this is a great time to learn. The kit comes with a drill bit or specifies which one to use. It also comes with a special tap. The tap is just the right size for the outside of the coil and its thread profile matches the profile of the outside of the coil. Notably, it's smaller than the next-size machine screw (#12 in your case), a significant factor when the hole is in a small ear and a larger hole would weaken the structure.

You re-drill the hole, then tap it with the special tap. The aftermarket units come with a tap handle on the mandrel, or you can use a standard tap handle.

This is the clever part. At one end of the coil, the wire is bent so it forms a diameter, right across its bore. If you were to attempt to screw the threaded insert into place with thumb and forefinger, you would conclude that the tap was undersized or the coil was too big. But when you slide the coil onto the mandrel, you see that the end of the mandrel has a flat or notch that accepts the bent end of the coil. As you attempt to screw the coil into the newly tapped hole, the mandrel winds the coil, tightening it and reducing the outside diameter. The coil is screwed in until the back end is flush. As you release torsion on the mandrel, the coil expands and locks into place. You can turn a screw in and out with no worries about unscrewing the coil. If your project needs to accept a screw that is longer than the insert, just insert the mandrel such that the end-wire is not in the notch, and tap the end of the mandrel. That cross-bore segment will break away at a narrow spot placed during manufacture.

This will be a much more robust fix than Loctite or JB Weld.

Let us know how it comes out.
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Old 10-28-2020, 11:08 PM   #10
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Larry,
Thanks for the explanation. After reading your first post, I did some research. The Ebay link you gave doesn't go well to Canada – $60 shipping charge!

But, I did find an E-Z Lok system on Amazon Canada for $35.71. I think I'll order it, since Amazon Prime should give free shipping. https://www.amazon.ca/Z-SK30620-Thre...N7PYTYPVMZGQFQ

I did find several YouTube discussions of these things. The most compelling one did some serious testing of various alternative systems and the helical insert systems were actually strong enough to break the bolt before they stripped.

–cheers, Gordon
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Old 10-29-2020, 06:45 AM   #11
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I just replaced ours with a SeaFlow 3 GPM pump. The SureFlow kept losing prime. So far it works like a champ.

We use it mostly for flushing the toilet when we stop for a potty break on the side of the road, most of our camping is in state parks and have water available.

https://www.campingworld.com/seaflo-...mp-118493.html
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Old 10-29-2020, 09:20 AM   #12
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Impressive test

Quote:
Originally Posted by gordonsick View Post
Larry,
Thanks for the explanation. After reading your first post, I did some research. The Ebay link you gave doesn't go well to Canada – $60 shipping charge!

But, I did find an E-Z Lok system on Amazon Canada for $35.71. I think I'll order it, since Amazon Prime should give free shipping. https://www.amazon.ca/Z-SK30620-Thre...N7PYTYPVMZGQFQ
Gordon,

That was an impressive test. (Some systematic error? All of them failed on the left side first.)

I saw several Ez-Lok offerings on US Amazon, with and without the drill bit. That seems to add $8-10 to the price. Please let us know how it comes out.

I have used these on some pretty serious repairs including the central drive shaft bearing mount on the 1962 Impala.
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Old 10-29-2020, 02:37 PM   #13
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Things are warming up next week and my coach should be sufficiently thawed to allow me to remove the pump without damaging the hoses.

It seems that these helical coils are used by a lot of manufacturers on their OEM factory products where threads go into soft castings. This explains why they are sold in bulk. That makes me inclined to repair all 8 of the screws on my pump.

I'll let you know how the installation goes, but I won't be able to really test the results until the spring.

–Gordon
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Old 10-29-2020, 08:22 PM   #14
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Forgot to mention

Quote:
Originally Posted by gordonsick View Post
Things are warming up next week and my coach should be sufficiently thawed to allow me to remove the pump without damaging the hoses.

It seems that these helical coils are used by a lot of manufacturers on their OEM factory products where threads go into soft castings. This explains why they are sold in bulk. That makes me inclined to repair all 8 of the screws on my pump.

I'll let you know how the installation goes, but I won't be able to really test the results until the spring.

–Gordon
Gordon, one thing I forgot to mention is that most of the 10-32 helical coils I looked at were 3/8" (0.375") long. I know you said the casting wasn't bored very deep. You may have to deepen the hole. If you need to leave it blind, you can cut the top off flush with the surface. The Dremel might be best for this.
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Old 10-30-2020, 10:02 AM   #15
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Larry,
All of the holes are open at the back, so I won't have a problem with a long coil. The 4 holes on the middle of the sides screw into a plate and behind the plate is the housing for the motor. I might have to open up more space on the housing. As you say, a Dremel is a good choice there.

BTW, I see that the original Helicoil comes with three taps that successively lead you to the last bottoming tap. The one I ordered only has one tap, so missing the bottoming tap, which could be a problem if my hole wasn't open at the back.

–Gordon
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