Aqua Hot recovery tank filling up

[timaz996]

What would cause my Aqua Hot recovery tank to fill up? Weak radiator cap? Or could my Aqua Hot have a leak and my water pressure forcing antifreeze back into the recovery tank?

[Dr4Film]

Two possibilities. Since you failed to post the model # of your Aqua-Hot I am assuming that you have the 100-01 Aqua-Hot unit. That has an internal fresh water loop located INSIDE the boiler tank. If that has a leak, that would cause your overflow tank to keep going up beyond the MAX HOT fill line. Second possibility is your Motor-aid feature that has another loop that goes inside your boiler tank which circulates coolant from your engine system. If that loop has a leak, that would also increase the level in your overflow tank.

[KevinH]

I was just at a FMCA a rally in Oklahoma . They had an Aqua hot service guy there. I’ve always done my own service in the past, but decided to have them service it this time. My canister chamber was cracked and had to be replaced. And they had one on their truck. They also have replacement units. For $6900. They take your old one out and replace it with a rebuilt one. The guys name is DeGerald services 501-258-8426. www.lloydsrvheating.com. They’re out of Paron Arkansas. Seems like a nice guy. He said I could call him anytime if I had any issues.

[timaz996]

Update,

I think it’s the return tube right at the radiator cap on the top because I noticed it dripping. My theory is it’s putting antifreeze back into the recovery tank but can’t create a vacuum to pull it back out. So I’m going to detach it cut a little bit off the end and put it back on to see what happens. Yes I do have a 100 series unit. 

[vito.a]

I recently replaced our Aqua Hot boiler.  On the older 100-01 models, the fresh water copper coil is on the outside of the boiler (see picture).  

I'd replace the radiator cap and monitor it.  Be careful removing the cap.  The filler neck is soldered on and can come lose.  

Good luck!

[96 EVO]

2 hours ago, timaz996 said:

Update,

I think it’s the return tube right at the radiator cap on the top because I noticed it dripping. My theory is it’s putting antifreeze back into the recovery tank but can’t create a vacuum to pull it back out. So I’m going to detach it cut a little bit off the end and put it back on to see what happens. Yes I do have a 100 series unit. 

Certainly worth a try!

[wamcneil]

2 hours ago, timaz996 said:

Update,

I think it’s the return tube right at the radiator cap on the top because I noticed it dripping. My theory is it’s putting antifreeze back into the recovery tank but can’t create a vacuum to pull it back out. So I’m going to detach it cut a little bit off the end and put it back on to see what happens. Yes I do have a 100 series unit. 

Hopefully that's your problem... And hopefully by "filling up" you mean that the coolant accumulates in your reservoir and stays there (doesn't return to the AH tank as it cools down). Your reservoir is just staying full, right? And not periodically overflowing? I'm not sure that would even be possible with an older unit like yours and mine.

The radiator cap housing is also a probable source of your problem. The housing is butt-joint soldered onto the thin edge of the vertical tube that goes down to the tank. It's a very weak solder joint and likes to crack. I think your theory is right. In my experience a leak in the housing will push coolant into the reservoir, and then air is drawn back in. Eventually it gets to the point where the coolant expands to the top of the tank and there's no more coolant to expel and it just stays in equilibrium.  

Fixing the filler neck is a horrendous pain, but Roger Berke has a preposterously expensive fix that may or may not work, depending on how little clearance you have above the filler cap. Personally, I just pulled off my pressure cap housing and inserted an expanding rubber plug in the tube and I'm running the system unpressurized. I have a plan to modify the system with a remote pressure cap, but there seems to be no issue running the system unpressurized.

It's not like it gets hot enough that boiling is a concern. I'm thinking maybe they pressurized the system to help keep the heat exchanger hoses from kinking and restricting flow.

Cheers,

Walter

Edited September 21, 2023 by wamcneil

[timaz996]

Thanks for everyone’s replies. I won’t be able to confirm it’s just the overflow tube until late Friday or Saturday because it is raining here in Island Park, Idaho until then. Yes, it has field the recovery tank to within about a couple inches of the top and has stopped. So I am hopeful that it is only a split on the rubber tube that goes to the nipple under the radiator cap. This has happened to me once before, so I guess I need to replace that clear rubber tube altogether.

Edited September 21, 2023 by timaz996

[Dr4Film]

10 hours ago, timaz996 said:

Update,

I think it’s the return tube right at the radiator cap on the top because I noticed it dripping. My theory is it’s putting antifreeze back into the recovery tank but can’t create a vacuum to pull it back out. So I’m going to detach it cut a little bit off the end and put it back on to see what happens. Yes I do have a 100 series unit. 

That's good to know however, there are 4 different versions of the 100 series so it's important to know the EXACT model number listed on the side of your Aqua-Hot.

These are the four models, 100-01, 100-02, 100-03 and 100-04.

The first two have the fresh water loop on the OUTSIDE of the boiler tank and the last two have the fresh water loop on the INSIDE of the boiler tank.

If you have one of the first two then ignore the first possibility that I had posted as that cannot happen. However, if you have either the 100-03 or 100-04 then it comes into play.

[timaz996]

16 minutes ago, Dr4Film said:

That's good to know however, there are 4 different versions of the 100 series so it's important to know the EXACT model number listed on the side of your Aqua-Hot.

These are the four models, 100-01, 100-02, 100-03 and 100-04.

The first two have the fresh water loop on the OUTSIDE of the boiler tank and the last two have the fresh water loop on the INSIDE of the boiler tank.

If you have one of the first two then ignore the first possibility that I had posted as that cannot happen. However, if you have either the 100-03 or 100-04 then it comes into play.

I have the 100-02 thanks 

[96 EVO]

16 minutes ago, timaz996 said:

I have the 100-02 thanks 

Good!

That eliminates fresh water filling the boiler tank, but not the engine heat system.

Crazy they didn't think up another model number with such a drastic design change between -02 and -03 🤔!