Have you used the Hydro-Hot Engine Pre-Heat???

[Russ Mann]

How often (if ever) do you use the Hydro-Hot Engine Preheat function? I realized that I seldom (if ever) have used it. The reason I'm asking is that I had an C9 engine water pump failure a few weeks ago (80K miles) and when we removed the water pump we found the top right 1 1/2" port was totally clogged with a silica mud/dirt. It was packed solid and very hard. The truck radiator shop says it's caused by no flow of coolant in that port for a long time and that heat over time caused a silica drop out.
I'm not positive but guessing that this top right port is where the Hydro-Hot pumps the engine coolant from to get heated by the diesel burner and then returned to the engine under pressure elsewhere. I'm hoping someone can confirm this for me.
I'm going to remove the water pump (only way to get at the hose on top right) and try to remove this crud from the hose with a hot pressure washer. Then I will flush the Hydro-Hot Preheat lines and pump to be sure I have good flow without restriction.

Has anyone had this problem before and what did you do to solve it? Do any of you just cycle the Hydro-Hot Engine Preheat just to check its operation? I will be cycling it in the future to see if I can avoid this issue.

Thanks for your help.

[David T. Richelderfer]

Interesting!  I am under the impression the engine's water pump circulates coolant to the AquaHot and dash heat when you're driving down the road... and through the same hoses that the AquaHot uses to heat the engine when the preheat function is on.  Perhaps someone will enlighten us on this question... separate hoses or the same hoses?

As to your question about engine preheat usage, we use ours several times every year.  We almost always use it after boondocking overnight when on the road home from Yuma in March.  A couple of our usual overnights on the drive home are Fallon or Winnemucca in Nevada, Burns Junction or Jordan Valley in Oregon, or Homedale, ID.  It has always worked as designed because I watch the Aladdin engine temp get upwards of 60F to 80F before firing it up.

[Bryan Beamon]

Russ, we run our hydro hot engine pre- heat about 10 times a year depending on our winter locations. We now have 150k on our C-9 and have not replaced our engine water pump. We did replace a engine water pump on our C-7 at 120k with no engine pre-heat.

[Fred Cook]

Ok, again I am new to Beaver and just got to ask... where is the pre-engine heat hydro-hot switch?

[Russ Mann]

Mine is by the kitchen sink with the Hydro-Hot controls. There is another switch to the left of the driver.

[David T. Richelderfer]

In our Beaver coach, the Diesel Burner ON/OFF switch and the Engine Preheat ON/OFF switch are located on the fore end of the upper kitchen cabinets.  Both switches have a green light beside them to show they are ON (lighted green) or OFF (not lighted green).  The AquaHot electric element water heater switch (labeled Hydronic Heater) is located in the main 110v power panel in the bedroom.

[Joel Ashley]

Russ, that switch at the driver's console is not for the HydroHot's function.  It should be for switching on a 110v engine block electric heater if installed.  It requires a 15 amp cord in the engine compartment to be plugged into an outlet. Many cars and pickups have the option, especially those sold in Canada or northern U.S. climes where subzero is winter's daily life.  So there are two much different ways of preheating the engine oil before beginning trips.  I'm not positive, but I believe not all coaches have block heaters, but may have the switch regardless.

David is correct in that engine coolant is circulated through the Hydronic unit;  automatically by the water pump anytime the engine is running, and when not it's circulated back through the engine block by an electric pump in the unit if the Preheat switch is on (not the one by the dash - "block heater" and "engine preheat" are different entities).

If you go to the Coach Assist section and drill down to the 2006 Monterey manual, it's PDF pages 286-287 will offer insight.

Joel

[Fred Cook]

Russ, that switch at the driver's console is not for the HydroHot's function.  It should be for switching on a 110v engine block electric heater if installed.  It requires a 15 amp cord in the engine compartment to be plugged into an outlet. Many cars and pickups have the option, especially those sold in Canada or northern U.S. climes where subzero is winter's daily life.  So there are two much different ways of preheating the engine oil before beginning trips.  I'm not positive, but I believe not all coaches have block heaters, but may have the switch regardless.

David is correct in that engine coolant is circulated through the Hydronic unit;  automatically by the water pump anytime the engine is running, and when not it's circulated back through the engine block by an electric pump in the unit if the Preheat switch is on (not the one by the dash - "block heater"and "engine preheat" are different entities).

If you go to the Coach Assist section and drill down to the 2006 Monterey manual, it's PDF pages 286-287 will offer insight.

Joel

 I don’t have a manual for my coach so I am having to ask a lot of questions.  I have searched and there is no preheat switch in my coach, at least, anyway I can’t find it. There is a Hydro hot switch on the kitchen cabinet that is diesel and another switch that is electric and there is a thermostat that controls the furnace. That is all I can find.

[Joel Ashley]

Susie and Marty Schenck, or anyone else with a similar model coach... might Fred have a Hurricane system instead of an AquaHot, and no preheat?

Joel

[Samuel Sperbeck]

Hi Joel,

We have a 2001 Beaver Patriot Thunder Brandywine and it has a Hydro Hot but no engine preheat. As with Fred's coach there are two switches for the Hydro Hot, one for diesel and one for electric. Plus a third blank switch location. I'm guessing the engine preheat was an option not included for some coaches.

Good luck, Sam

[Joel Ashley]

So I don't know how complicated or expensive it might be, but is it conceivable for a (4th?) pump to be added to a coach that has an AquaHot without preheat, such as Fred's and Sam's?  Or has no one here explored that notion?  We've parked many times where it behooved me to warm the engine for an hour or two before departure following a night of 30 - 40 degree temps.

As the manual notes, the engine can't really reach full power until it's at about 80 degrees.  You might get it there okay by the time you get out of the park and on the road, but it seems prudent for the engine's sake to get it close to that before even starting, and the preheat is great for that.  Yeah, I know you can crank at much lower engine temps okay with today's oils, but if I can make it a bit easier on the starter and other components I will.

As to Russ' hose full of gunk, I presume the preheat and the engine heat hydronic supplement functions use the same hoses, so whether pumped forward by the water pump or backwards by the hydronic pump, coolant should have been regularly flowing in those lines, and the buildup isn't from stagnation.  If the shop is correct, then might there be some other reason, perhaps at the hydronic end, that coolant was not flowing?  Do we know yet for certain that the water pump upper port described is the hydronics one?  Regardless of whether one has the preheat option, most will use the water pump to cycle coolant through the hydronic unit at least while on the road, and thus have connecting hoses.

Joel

[Fred Cook]

Sorry, I did not mean to hijack this thread but... since I do not have the engine pre-heat option does that mean the engine does not cycle coolant into the heaters while driving down the road to keep the the coach warm instead of using the hydro hot system?

[Joel Ashley]

My take, Fred, is that most coaches do cycle engine coolant forward through the hydronics unit and back, at least with AquaHot/HydroHot units. 

But that heat will do you no good if you don't turn the thermostat and HydroHot diesel switch on while on the road so the heat exchanger fans on the floor can run.  The engine doesn't cycle directly to the exchangers, but rather through a loop in your HydroHot.  The coolant heat transfers there to special hydronic fluid, and then your HydroHot uses its own pumps to move that fluid, not engine coolant, to your floor exchangers. 

You will have to burn a little extra diesel to run the HydroHot while on the road, but the engine coolant is supplying a good deal of the heat, so the burner doesn't have to run as much as it would if you were just parked.  For most of us experience has taught that the house heat provides more actual comfort while on the road than the dash heat, which like a car is provided via engine coolant directly, but unlike a car is sourced 30+ feet away.  That's a lot of distance over which heat can be lost, and the dash fan can't push as much warm air as several floor exchangers.

On rare occasions in milder weather, we've found the dash heat (or AC) to be adequate, and got by without burning HydroHot diesel on the road.  But if the wife complains about "freezing to death" over there by the drafty entry door, I pull over and turn on the house heat, but keep the dash heat on, making sure her dash outlets are directed properly.

Joel

[Russ Mann]

Joel,
Quote:As to Russ' hose full of gunk, I presume the preheat and the engine heat hydronic supplement functions use the same hoses, so whether pumped forward by the water pump or backwards by the hydronic pump, coolant should have been regularly flowing in those lines, and the buildup isn't from stagnation.  If the shop is correct, then might there be some other reason, perhaps at the hydronic end, that coolant was not flowing?  Do we know yet for certain that the water pump upper port described is the hydronics one?  Regardless of whether one has the preheat option, most will use the water pump to cycle coolant through the hydronic unit at least while on the road, and thus have connecting hoses.

I've asked around about that hose and have not gotten an answer. We are planning to tear it down and I will chase that hose the hard way (crawling around under the coach is not easy anymore) and let you know. My limited electric pump experience says that flow won't travel through the pump unless it's turned on (maybe the 10psi or so from the water pump is enough to push it). Nothing could have flowed through that blocked port and my engine temps were normal, 192F-198F (before the water pump failure) and my dash heater worked fantastically so I don't know where else engine coolant would go except to the hydro hot, and thoughts to enlighten me would be helpful.

I may have other problems because when I turn on the Hydro Hot pre-heat my diesel burner does NOT turn on and I do not hear a pump running. The pump may be clogged with silica as well and burned up the pump. Something else to check. Does your heater turn on and can you hear a pump?

Thanks for all the input!

[Joel Ashley]

I'm probably in over my head here, as others on the Forum are far more knowledgeable about both the engine and the hydronics.  I've never turned on the Preheat switch without having the burner switch on also, since what would be the point of circulating unheated coolant.  I have to assume, since the burner switch also functions as a system reset when clearing faults, that the preheat pump won't start otherwise anyway, perhaps locked out unless either the diesel or electric switches are on.  Just guessing however.

Did you say, Russ, that you had consulted the AquaHot documents at the Club's Coach Assist page?  I believe the pumps for the zones are accessible by removing the hydronic unit's cover, and preheat could be pump #3 or 4.  Having someone slowly switch the preheat on and off while you listen outside at the unit may help sort which is the right one.  I understand the pumps' external valves can stick, and Bill Sprague says rapping with a hammer can free them.  A call to fellow club member, Orman Claxton. may provide some guidance.

Joel