Engine Heat

[Ray Davis]

Many of the Marathon's have two solenoid vavles in the engine area. One is normally closed, and one is normally open. If you turn on your heater, the Webasto fires, and by default, the return path does not go through the engine.

If you hit the "Block Heat" switch on the drivers dash (not the block heat in the electrical panel), then these two solenoids are reversed, and return coolant is sent through the engine before returning to the webasto.

It's great IF it works. In my case, and Adam DeGraf's case, the solenoid valves were clogged and not functional causing an issue. (I still have to fix mine). In speaking with Marathon, they are now removing the guts of the two valves, and letting the water cycle in both areas, all the time. Evidently this is what they did for Adam at a recent service in Coburg.

I hope to get some time perhaps this weekend to try to clean the valves, and see if that clears the issue. The solenoid valves are not cheap, and I'd rather not replace, if possible.

Anyway, that's how (some) Marathon's do it.

Ray

[dalej]

The way I'm thinking this valve works is like this. Point A flows to B all the time. There is somthing in the diverter valve that heats up and opens flow from C to D.

Do you guys this this is correct.

[dalej]

Ray, that's what I thought was the case in most newer coachs. I just didn't know if I wanted to go to the work of updating ours to that style.

What I have seems fairly simple, but I have to always have my engine heating. I could put a manual valve in the engine area and just restrict flow when I don't want to heat the engine.

I was also wondering about using the Wabasto to just heat the engine and not the rest of the coach, for the rare times I have been gone and the weather has turned and I need fast heat for the motor.

[Ray Davis]

I was also wondering about using the Wabasto to just heat the engine and not the rest of the coach

On my coach, if you hit the dash block heat, besides reversing the two return solenoids, it also starts the webasto, but does not actuate the valve which runs to the heaters. I do believe there is a manual valve which goes to the water heaters, but it's generally always open.

So, in the case of just trying to heat the engine, it's "supposed" to be a matter of simply turning on block heat, without requesting heat from the inside thermostats.

Ray

[JIM CHALOUPKA]

The way I'm thinking this valve works is like this. Point A flows to B all the time. There is somthing in the diverter valve that heats up and opens flow from C to D.

Do you guys this this is correct.

Dale, I think the valve works this way.

It is for the engine to come to temp. on it's own without the aid of the Webasto.
To get it done in the shortest time, some circuits are shut off until the engine is at temp..

So, looking at your diagram, I think it is C to B until the engine is up to temp.

The valve then opens and it is from C to D and A to B.

The D flow then goes through the Webasto (which is off) through the hot water tank or compartment heater or Summer Winter circuit (options) to heat some or all of them without burning the Webasto.

What do you think?

JIM

[gmcbuffalo]

Dale

In the diagram the flow from A to B is a pass thru and I think the flow from C to D is a second pass thru. In my diagram the flow from the engine goes to C and out D to Webasto then to registers back to diverter Port A to B and back to engine. If I shut off the Return and Supply valve on the engine the flow in the system would stop. Therefore I think that the diverter works on pressure and if the flow can't go to the engine then the return flow from the registers is diverter to port D ,since the flow out of B is closed because of the down stream return shut off valve on the engine. Therefore the webasto can keep working with the engine closed off from the system.

GregM

[truk4u]

Dale,

My Liberty is like yours. When the Wabasto is on, everything gets heated. The engine, hot water and all heat exchangers for the house furnace get toasty. There is also a water bay heat exchanger.

Nothing like a 160 degree engine temp when starting on a cold day, no smoke and no missing.

[jimshoen]

Ray,
I believe your coach is likely plumbed up the same as mine. Recently I replaced the two solenoid valves just aft of the Webasto. Additionally I added Y-Type strainers and ball valve shut offs to isolate the valves. There should be three seperate switches in your coach that fire the Webasto. One for engine preheat, another to supply hot coolant to the heat exchangers inside coach, and lastly one to heat domestic hot water. The way Marathon has the system designed is very good but difficult to understand. I have posted on this previously and would be happy to talk with you 775-843-8656.

When you select only the engine preheat (on mine labled System Heat) you will heat both the domestic hot water and the preheat the engine.

When you select only 12 Volt Water Heater you will only heat the domestic hot water. This is nice because it works fast, 20 minutes or less.

When you select only 12 Volt Heat you will heat the domestic hot water and send hot coolant to the heat exchangers in the coach.

Note, that no mater which button you chose you are always heating domestic hot water when the Webasto is running.

Now comes the fun part. What happens when you have more than one button pushed at the the same time.

If 12 Volt Heat and Engine Preheat are selected you will supply hot coolant to the heat exchangers inside coach, preheat engine, and heat domestic hot water. Pushing the 12 Volt Water Heater button along with the two above does nothing additional.

If 12 Volt Heat and 12 Volt Water Heater are selected you will be supplying hot coolant to the heat exchanges inside coach and heating the domestic hot water. 'No engine preheat.'

So what is the big deal? With a 40,000 BTU Webasto and real cold weather we are a little light on BTU's. I have checked this out with OAT's below 10 F.
If the coach is cold soaked and you fire up the Webasto calling for Engine Preheat, Domestic Hot Water and, Coach interior heat you will be waiting a long time to get everything warmed up. So what do I do in these situations.
Ususally I will only call for engine preheat first. Let the Webasto Preheat engine and domestic water only. Now you can start engine and everything is good. Once the engine is preheated switch over the 12 Volt Heat for the interior. If you are plugged in or want to run the generator you can be running the 110 Volt Heat while the engine preheats.
With the engine preheated you have also heated the domestic water. Now we want to heat the interior of the coach asap. Switch over to 12 Volt Heat only and close that manual valve which should be slightly forward and slightly above the Webasto. Now you will have all 40,000 BTU's going into the coach and it will heat up quickly. Hear is the catch, you must make sure to reopen that manual valve before activating anything other that 12 Volt Heat. In any case, the better you understand the system, the more options you have to get what you want when you need it.
I was always curious why the recommendation was to remove the guts from the two controlling valves. Bottom line, few owners want to take the time or energy to understand and maintain this system. In really cold conditions the extra heat inside is very nice especially for the 2000 and older XL's.
When you are driving the bus and want to use the heat from the engine to heat the inside of bus and domestic hot water you need to select both the Engine Preheat (System Heat) and 12 Volt Heat. Then the Webasto only fires the burner when the coolant temperature drops below something like 160F. When ever you select 12 Volt Heat to heat inside coach and you are calling for heat at the thermostat an auxillary coolant circulation pump in the ceiling of the spare tire compartment will be on. This pump assists the Webasto coolant pump in getting the heated coolant all the way to the front of the coach and back. If then auxillary pump is not working you will not get heat inside coach.

[garyde]

So if you remove the solonoids, you have the same heating system as the Libertys. Liberty has gate and ball valves to shut off any one system or all systems. Or, If you don't turn on the T-stats , no heat to the interior. But, I'm not sure what this has to do with
Dale's original post regarding the Thermostat. Dale I'm sure there are new in line mechanical thermostats you can buy and keep it simple.

[jimshoen]

OK, back to Dale's question?
Sorry I have no idea what that is.
Took me two years just to figure out what I have.