Hydro Hot Coolant Leak in Dash Area

[Randy Stephenson]

I discovered coolant leaking on top of my front mounted generator.  So, I moved the generator out far enough to crawl up and reach into a very small and hard to get to compartment in the dash area.  I discovered what appears to be a control valve with 6 hoses going to it, along with evidence of dripping coolant.

I wiped all the coolant off and was able to tighten the hose clamps (they all required a couple of turns to snug up, so thought I found the cause of the the leak).  I started the MH for 5minutes or so and there was not a leak for about an 1/2 afterwards.  Proceeded to move the generator back into position, hooked up all the wires and power assist.  Backed the MH into the barn thinking I was all set.  The next day there is was still a small drip of coolant.  I'm thinking it is pressure related.  So, I have to go back at it.

When I was reaching up into the compartment, I saw what appeared to be an accessory panel (light was shinning through the silicone sealed edges of a wood panel). Therefore, I am now thinking the best way to get after the leak is through the inside of the MH.

Has anyone experienced this type of leak?  And you ever taken the dash cover off to get to the upper portion of the dash box?  I am afraid the black control valve may be cracked, hence, the cause of the leak.  It would be extremely difficult to remove the control valve from under the MH through the small compartment.   

Randy

[Steve Huber Co-Admin]

Randy,
Sounds like an antifreeze leak in the line or heater control box for the dash and not related to the Hydro Hot. (Picture might help). I doubt you will gain much by removing the dash cover as I think the control, heater lines and heater core are all outside the dash firewall. The dash cover will come off by removing the hold down screws. Not too bad a task. If you don't need the dash heater and want to stop the leak w/o fixing it you can clamp off the 2 lines coming from the engine with line clamps or needle nose vise grips.
Steve

[Randy Stephenson]

Thanks Steve, I'll check further.  I thought the front heat was based on Hydro Hot system (like the floor register up front).   I didn't think the engine coolant went up to the dash.  Looks like I will need to crawl back under for second try.

[Gerald Farris]

Randy,
A coolant leak from above the generator on your coach is caused by one of three things. The first and most likely is the heater core. The other two options are the heater control valve (if equipped) or a hose. The heater control valve is a vacuum operated valve that cuts off the flow of engine coolant when the heater is not being used to increase the efficiency of the dash A/C. If you have a heater control valve and it is leaking, you can just use a hose splice connector and bypass it until you get a replacement.

If your heater core if leaking, it can be a pretty big job because the dash HVAC case has to be removed to replace the heater core that is inside it. However if you had rather no replace a leaking heater core, you can just take the two hose that go to the heater core above the generator and use a hose splicing connector to hook them together. This will keep all the functions of coach heat from the Aqua Hot by using engine heat as well a engine preheat from the Aqua Hot. If you bypass the heater core by using cutoff valves at the engine or hooking the hoses together at the engine, you also take the Aqua Hot system out of the engine coolant loop.

Gerald 

[Steve Huber Co-Admin]

Thanks Gerald,
I'd forgotten about the Aqua Hot tie in.
Steve

[Randy Stephenson]

Thanks Gerald, based on your and Steve's feedback, I'm going to pull the generator out again and take a better look with a mirror (opening is too small to get a head up there for a good look).  I did see the mixing valve, hopefully it's a hose clamp issue.

[Bill Sprague]

With both Gerald and Steve weighing in, my approach will indeed sound weird!

Somewhere around year 6 on our '04 Monterey I saw coolant on top of the Onan.  I didn't know where it came from or how much was leaking.   (Get ready for the weird part....)

I had some spare aluminum grease pans from my Weber.  I taped them to the top of the generator to catch the coolant.   Three stayed dry.  One would collect a tablespoon or so.  Based on the location of the "wet" pan, I was able to locate a hose connection above it with a loose clamp.  No, it was not easy to reach it, but I was able to tighten it enough to stop the drip. 

To be sure, I left the pans there for a couple months to be sure they stayed dry.  Comments and questions from fellow RVers may alone have been worth the weird troubleshooting.

Good luck!  Coolant leaks are stressful.
 

[Edward Buker]

Randy,

There have been times when using my Iphone and taking a series of shots from various angles and then enlarging and possibly adjusting them for brightness on the phone, Ipad, or a computer has yielded views and things I could not see with a mirror. Especially helpful for reading part numbers and at times seeing leaks or stains from leak trails that have dried.  My eyes aren't what they used to be and I am certainly not as flexible as need be at times and the camera has been helpful.

Later Ed

[Randy Stephenson]

Gerald, Steve and Edward, thanks for the tips.  Fortunately, my previous work of tightening hose clamps stopped the leak!  Apparently, there was residual coolant on a structure member or wiring loom (which must of dripped off when I backed the Beaver into the barn for the night).

After a nights sleep, figured that I should get the temperature and pressure up and check once more.  Today I took her out for a short ride until reaching 180 degrees, on return the top of the generator was dry, and stayed dry the balance of the day!

I also learned that if the front generator body panel is taken off and the generator returned to the park position, the upper heater control valve is a much easier to reach.  No need to pull the generator out past the rail system and climb up behind it to get to the area.

Was able to take a picture as suggested, will post in case anyone else runs into this issue.

[Randy Stephenson]

Here is a photo of the control valve and attaching hoses.

[Joel Ashley]

Thanks for the idea (and my regular "duh" moment), Randy.  It's likely many jobs might be made easier behind the cap by just removing that panel, rather than trying to work around an extended genset, the most obvious and generally attempted access route. 

Joel

[Randy Stephenson]

Joel, That's what is so great about this forum.  Learning from others before proceeding on repairs sure make things easier. 

On a side note regarding moving the generator all the way forward, I was able to sand and repaint the generator framework around the lower perimeter, looks like new now! 

[Joel Ashley]

Cool, Randy!  Now you can come and paint mine  .  Been wanting to get under there with POR-15 paint for years.

Joel

[Randy Stephenson]

Joel:

I hope to get out you way in the Beaver in a few years, since I am in Michigan it's a retirement trip.  Been to Portland and Seattle on business many times, via airplanes.