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Topic: Aqua Hot Leak (Read 1663 times) previous topic - next topic

Aqua Hot Leak

I apparently have a small coolant fluid leak in my Aqua Hot.  The Aqua Hot in my '99 U320 is mounted amidship between the battery bay and the propane bay.  It is accessed on its aft side through the storage bay, so you cannot see much of it. 

The fluid is collecting on the floor of the bay at the rate of about a cup a week.  (Thankfully the Foretravel is so well sealed that the bay is water tight and the fluid is not migrating to other bays or onto the ground.)  This is with the motor home in enclosed storage with the furnace set on about 50 degrees. 

I have removed the access cover and inspected the unit as thoroughly as I can from the one side that is accessible and cannot see where the leak is coming from. 

It looks to me that it would be a very major job to pull the Aqua Hot out to inspect it.  I would have to start by removing both Joey Beds then deal with all the hose and wiring connections, not to mention the fact that it looks really heavy. 

My question is, "Has anyone else had a similar problem and how did you deal with it?" 

Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Aqua Hot Leak

Reply #1 –
Not sure if this is the problem you are having, but I know of a number of '99s, including mine, that have developed a coolant leak at the copper elbow on the line from the engine coolant pump to the Aquahot.

I "fixed" mine by removing the engine to/from hoses from the Aquahot and connecting them together with a 3/4" plastic barb fitting. Now I have no engine preheat. I also removed the engine coolant pump fuse to keep from inadvertently turning it on and running it dry.

Fixing it requires a small contorsionist. Would guess that you need to remove the burner head, make sure the engine preheat loop is dry and then sweat on a new elbow. Roger Berke has seen (and fixed a few) these and sent me the attached picture. The elbow in question is circled and is behind the burner. I needed a mirror to confirm that was where my leak was.

Re: Aqua Hot Leak

Reply #2 –
Thank you, Bob.  This is exactly the reply I was hoping for.  I will get out my mirror and see if that is where my leak is.
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Aqua Hot Leak

Reply #3 –
If you can determine if it is engine coolant or Aqua-Hot coolant is leaking will give you somewhere to start looking.

If you are loosing engine coolant, then it is probably the copper elbow that has developed a crack in the inside corner of the fitting shown above.

If it is Aqua-Hot coolant, I can give you some common spots that leak.

- Roger Berke -
2000 Foretravel U320 42ft

Re: Aqua Hot Leak

Reply #4 –
Roger,  As as matter of fact, it is the Aqua Hot coolant which is being depleted.  The expansion tank for the engine has stayed at its normal level and the expansion tank for the AH has needed to be replenished.  So, any other suggestions would be appreciated.  Thanks
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Aqua Hot Leak

Reply #5 –
Check radiator cap.  If there is any question, replace it.  Use 'standard' automotive 13# cap that you can purchase anywhere.  Also check the hose that runs between the radiator cap and overflow bottle.  It is not unusual for hose to crack and leak.

Check around zone pumps for leaks.  If they leak, then there should be coolant residue below the pumps.  There is an "O" ring in the pumps that gets hard and fails.  Unfortunately you have to remove the pump(s) to replace it, which is a terrible job.

If you do not see where leak is coming from, then use radiator pressure tester to pressurize system to around 15#.  Any small leak will become pretty obvious.  You can rent pressure tester.

Let us know what you find.

- Roger Berke -

Re: Aqua Hot Leak

Reply #6 –
When I first got this 96 U320 the AH had a couple of leaks first was the expansion tank had a small crack on the back side of the tank and the hose to the tank was bad and fittings where the hoses attached the fittings leaked,  I ordered a new tank and hose from AH tightened the brass fittings and a new radiator cap from Napa Auto parts and so far so good. Art 
Art
1997 Prevost 40'
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Re: Aqua Hot Leak

Reply #7 –
The source of the leak turns out to be a stress crack on a copper "T" fitting which directs hot fluid to one of the three zone pumps.  It does not look like an easy fix.  (Roger, I sent you a PM on this subject)The selected media item is not currently available.
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Aqua Hot Leak

Reply #8 –
Richard

I prefer to answer your question here on the Forum so that others may benefit.

I had a leak in this exact spot on my coach that I caused when I replaced all of my circulation pumps.  It was a cold solder joint that was not leaking until I disturbed the pipe.  I had to disassemble the unit again after I had replaced the pumps to repair this leak.

To repair this leak you have to remove all three of the zone pumps to get enough room to unscrew this copper fitting from the valve.  Once you get the copper manifold piece out, it becomes a pretty simple re-solder job on the copper fittings.  There really is not an easy way to do this.  You are going to get some coolant spillage and there is not really enough room to get a container under the pipes to catch it.

I have one of these manifold pieces that came out of a scrapped Aqua-Hot if that would be easier for you.  I have some concern that it may be of slightly different size (length) as these parts may not be standard.  Contact me directly for more information.

You also had some concerns about running zone with no coolant in the pump.  The pumps are remarkably rugged and I would guess that the pump is fine.  If you ran the zone out of coolant, you have to prime it as the pumps are not self-priming.  This is a terrible job in itself.

I think that your leak is in the location circled on the photo below.

- Roger Berke -

Re: Aqua Hot Leak

Reply #9 –
Roger, would that super tape work, room permitting, for a temp. fix, also as a prevent, what do you recommend one could do to keep this from happening in the first place? What are the pressures on this fitting?  thanks jc
JC
1999 U320

Re: Aqua Hot Leak

Reply #10 –
Well, I have just returned from removing the three zone pumps and the manifold.  It was not as horrible a job as I expected.  I plan on inspecting the pump bodies in detail to determine their status.  I believe the stress crack is due to a support clamp being loose.  There is a vertical rod with a clamp around the left end of the manifold which supports the outer end of the manifold.  The clamp was loose (probably for a long time) which forced the weight of the manifold and the three pumps to be cantilevered on the copper pipe.  Thus the stress crack. 
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Aqua Hot Leak

Reply #11 –
I disassembled two of the zone pumps and they are just fine.  The engineering of them is very interesting.  I am a veteran of many rebuilds of Volva-Penta coolant pumps and expected to need to replace the impeller on these pumps. 

I understand now why they are not self priming.  I also understand the need for the check valve just above them which tends to hold the coolant in the pump body when they are not in use. 

Any advice on the "terrible job" of how to prime them once I get everything back together would be appreciated. 
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Aqua Hot Leak

Reply #12 –
Richard,

Once you have reinstalled the pumps and have the coolant tank full of antifreeze, use an automotive radiator tester to pump the pressure to 13 to 15 pounds.  This will force the fluid into the pump to prime it.  Works great.

If you turn the pump on just before you pump up the pressure, you should hear the pump noise change as it primes and begins to pump fluid.

Radiator pressure testers are at most auto parts stores (about $80) and there may be some available for rent.

All the best on your repair.
Rudy Legett
2003 U320 4010 ISM 450 hp
2001 U320 4220 ISM 450 hp
1995 U320 M11 400 hp
1990 Granvilla 300 hp 3208T
Aqua Hot Service Houston and Southeast Texas

Re: Aqua Hot Leak

Reply #13 –
Thank you Rudy.  That sounds to me like a very good way to prime the pumps. 

The resources on this forum are truly amazing.
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Aqua Hot Leak

Reply #14 –
There are excellent directions on how to bleed the coolant lines on the Aqua-Hot website, here: 
https://www.aquahotparts.com/eSource/ecom/eSource/default/Line_Bleeding.aspx

I use a radiator pressure tester to pressurize the boiler tank.

I have also had some success with filling the pump with coolant prior to installing the check valve on top of the pump by using funnel to fill the pump and the manifold.

You also need to be VERY careful not to damage the pipe that is beyond the coolant shut off valve that goes to the boiler tank.  It would be impossible to repair.

- Roger Berke -

Re: Aqua Hot Leak

Reply #15 –
Quote from: hotonthetrail –
Roger, would that super tape work, room permitting, for a temp. fix, also as a prevent, what do you recommend one could do to keep this from happening in the first place? What are the pressures on this fitting?  thanks jc

I do not think so.  You have to disassemble the pump manifold and re-solder the copper lines.

- Roger Berke -

Re: Aqua Hot Leak

Reply #16 –
Success!!!  We again have heat.  I found a local plumber who replaced the copper "T" in the manifold.  I then reinstalled the manifold and zone pumps.  I used a radiator pressure tester, which I was able to "borrow" from O'reilly Auto Parts, to push fluid up through the three zone pumps.  After all the plumbing was tightened down, I pressurized the system to about 16psi for an hour with no leaks found.  I then reinstalled the diesel burner body and made all the electrical connections and voila!! 

All-in-all the job was not that bad.  I ended up with antifreeze up to my elbows, or more correctly because of the geometry of the working space, down to my elbows.  I am getting a little old for working long periods in cramped spaces, but who isn't. 

Thanks to all on the forum who offered help and suggestions. 
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Aqua Hot Leak

Reply #17 –
Richard

Congratulations on your successful repair.

I have not figured out how to do this type of repair without being covered with coolant.

- Roger Berke