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Topic: Shurflow 4008 - Overhaul or Replace (Read 341 times) previous topic - next topic
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Shurflow 4008 - Overhaul or Replace
I have a 2019 MidBath and have noted that after sanitizing my water system, when I purge air and refill the lines with water, the water pump runs even after all air has been eliminated from hot water heater and lines to kitchen faucet, lavatory faucet and shower.  Pump shuts off when I "rap" it with my knuckle making me suspect a sticking valve in the pump head.  I'm hence inclined to replace the head unit, rather than the entire pump ($23 vs $100). 

Am I missing something here?  Other/better ideas?

Thanks,

Warren
Warren
2019 MB “Dream Catcher”
Jeep Wrangler JL
Re: Shurflow 4008 - Overhaul or Replace
Reply #1 –
There are eight bolts around the perimeter of the pump head. Remove only the four in the corners to separate the pump. scribe alignment marks on all parts you remove to assure correct orientation on re-assembly, if you elect to disassemble the pump parts. The check valve is part of the pressure switch, and you may simply have to clean and lube all parts to restore performance.

Steve
2004 FL
2013 Honda Fit
Re: Shurflow 4008 - Overhaul or Replace
Reply #3 –

Suspect the pressure switch is sticking, it's replaceable.
Amazon.com: SHURFLO 94-800-00 Model 4008 Repair Parts-Complete Upper...

A bad water pump, when camped far away from an RV shop, can ruin a weekend. We have carried spare pumps for many years and they have been used by us or installed in a friend's LD, when their pump unexpectedly died.
Since your pump is near new, I would buy a new pump head, with the switch and consider buying a spare pump.

Larry

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Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Shurflow 4008 - Overhaul or Replace
Reply #4 –
"Am I missing something here?  Other/better ideas?"

I hope you are aware that you can adjust for pressure with the tiny Allen screws in the pump head. All it may take is a tweak. The trick is finding the correct size Allen wrench and guiding it to the proper location.   :o  Good luck with that!
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Shurflow 4008 - Overhaul or Replace
Reply #5 –
Hi Warren. Could it just be pressurizing the air 'cushion' in your water heater?  Mine runs for 5-10 seconds, then stops. If you turn off your pump, and you can still get a good amount of water out of the tap, then it is working well. Otherwise, adjustment of the pressure switch sounds like 'good to try'. At the age of your pump, I doubt that anything is worn out.  RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Shurflow 4008 - Overhaul or Replace
Reply #6 –
Thanks Guys for the many good ideas!  I think I'll proceed in this order:

1) Call Shuflo for any additional guidance and to request they provide under warranty, a new pump (or head unit if they deny entire pump).

2) Check that the water heater air cushion has formed - I suspect this is not the issue as I allow the pump to run for 20-30 seconds after air has stopped flowing through the faucets.

3) Check for a clogged valve (I once had a Shurflo pump that was clogged with poly drill tailings left behind by SOB manufacturing). 

4) If problem persists, replace Head Unit (hopefully with a warranty part).

5) Purchase a replacement pump as a spare, if needed.

I'll report back but will need to retrieve our coach from its storage garage in Nipomo before I begin this work as well as other periodic maintenance.

Thanks again!

Warren
Warren
2019 MB “Dream Catcher”
Jeep Wrangler JL
Re: Shurflow 4008 - Overhaul or Replace
Reply #7 –
Quote from: Lazy Bones  - 
I hope you are aware that you can adjust for pressure with the tiny Allen screws in the pump head. All it may take is a tweak. The trick is finding the correct size Allen wrench and guiding it to the proper location.  :o  Good luck with that!

I don't  think it would be wise to do these adjustments - it is unlikely they would have changed on their own from when the pump was working properly...

Steve
2004 FL
2013 Honda Fit
Re: Shurflow 4008 - Overhaul or Replace
Reply #8 –
"... it is unlikely they would have changed on their own..."

Mine didn't change itself! When the previous pump went south I ordered a replacement from e-Trailer. After all the contortions I had to go through to install it (30'IB, under the bed) it would run on a bit after closing the faucet. Some investigation taught me that an adjustment was in order. I did find the correct Allen wrench but the clearance I had to work with, up against a wall, and the fact that my arthritis wouldn't allow it, I finally took it to Vince at the factory. He was not happy with the prospect (apparently it wasn't the first time) but eventually he did the deed and it has been working now for the past three years.  ::)   8)
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Shurflow 4008 - Overhaul or Replace
Reply #9 –
Warren

It might be a coincident, but with a near new pump and the problem first occurring after flushing, there is a good chance there is still air trapped somewhere in the system,  longer flushing time may be needed.
After driving on a partially filled tank, our LD's water pump will sometimes lose its prime and runs continuously until the system is flushed by opening a faucet. It sometimes takes a minute or two before the pump primes and starts pumping normally.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Shurflow 4008 - Overhaul or Replace
Reply #10 –
There was a thread a while back about adjusting the bypass pressure on the 4008 pump. Would this apply here? I know when I
replaced our pump, it required a little adjustment.

Jon
1994 MB
Re: Shurflow 4008 - Overhaul or Replace
Reply #11 –
I spoke with a Shurflow representative. He suggested that since the pump works fine after tapping it during priming, the cause is unlikely to be the pressure settings. He agreed that a more likely explanation is more run time required to pressurize the hot water heater and hence develop the necessary back pressure (as Ron suggested). I’ll check it out when I’m able to retrieve our coach from storage, and reply again.

Thanks for the thought and input.

Warren
Warren
2019 MB “Dream Catcher”
Jeep Wrangler JL