4104 dash heat and defroster

[Nel]

Hello all, first time we will be cool weather camping next weekend and I have never used the dash heat or defroster on my 4104, I know there is coolant in the lines because I was going to remove the under floor radiator but just by past it instead so I did loose some coolant and the dash fans work. So my question is besides opening the valves on the rear bulk head (look original) anything else I need to do or look for ? How do I bleed the air out of the lines and do those valves have a tendency to leak once I mess with them? The engine coolant and radiator work fine now so I don't want to mess with it if causes a reliability issue since I wont have much time to work on it if it does, Thanks

[chessie4905]

The defroster core lays horizontally above defroster fans. There is a push- pull valve at your right knee that regulates a valve in heater hose feeding the defroster core. Make sure valve is open; you may need to disconnect hose to verify it works as designed. In top left of core there is a bleeder screw to get out trapped air. We left main under floor heater core and motors in our  4104. They worked well in cold weather. BTW, the heater core is the same one as in the 4905.

[Nel]

Thanks, Chessie, did you have to open the valves in the engine compartment?

[Dave5Cs]

If it has not been opened in a long time I would not open the valves in the engine bay until you drain the system and clean it out, check for any leaks and then put in new heavy duty coolant or at least check it for additives with coolant strips ( NAPA has them). You could be mixing junk coolant with good and the engine may not like that. Just sayin

[dtcerrato]

Nel here's a photo taken back in the early 80s of the 4104 defroster. We abandoned the original valve & updated it to a later brass ball valve & extended the handle so the driver could access it easily. The little air bleed screw is in the upper left hand corner of the core as pictured just above the upper line going into the core. Down under the bus extreme front toward passenger side are two 3/8 copper lines that drain the core, one is wet drain the other lets air in so water flows to drain, the small valves are accessible inside the bus under the defroster unit in an empty space there, that would be for draining where the above mentioned air bleeder would be for when filling the system. If you haven't used the defroster core, you will love it when cold. On high it will raise the temp in the drivers area & beyond. There is a lever at the right knee when sitting that mixes the air to circulate (move just inside air) or ventilate (bring in outside air). Also a diverter flap forward & lower than that lever that diverts air up (to windshield) or down (to feet/floor) or anywhere in between. Our whole system was removed & restored as most of its functions were froze from rust or dirt.

[dtcerrato]

Forgot to mention that when the valves in the engine house are open the defroster is circulated hot coolant temp weather the larger under floor radiator core valve for the main heater blowers is open or not...

[chessie4905]

We left them open except in summer time.

[richard5933]

I've read in a couple of places that leaving these valve open year round is preferable. I cannot remember where, but the explanation went something like this...

The increased flow is good for helping increase the volume of coolant when the system needs it to help cool the engine better. Valves have a tendency to leak when only operated once or twice a year. You never know when you'll need to clear the inside of the windshield of moisture on a cool evening. Having the ability to run the boost pump through the full system helps to 'burp' the system when filling/refilling. They are not easy to get to. And there were more, but I can't remember right now.

I'm sure that there are also good reasons for closing the valves in summer, but none come to mind right now. It was explained to me that the only time they are generally closed would be to isolate the engine portion of the system (for instance, replacing a thermostat or doing repairs to radiator). That way, it would not be necessary to drain all the way to the front and re-bleed the system when refilling.

YMMV
Richard

[chessie4905]

If the valve leaks, tighten the packing nut slightly. 4104s rarely had heating issues, unless radiator needed cleaning or shrouds were missing. They had shutters to keep them from running too cool in moderate weather.
The defroster case has a drain at bottom of vee with a hose connected to exit at bottom of coach behind bumper. You can tell if defroster radiator is leaking by damp or wet spot when parked for a day or more.

[Nel]

Thanks for the responses, will give it a shot , Dan , I can see my valve has been relocated in the front according to your picture and good to know it works so well when operating right, Thanks again for all the info.

[Nel]

I worked on it today , noticed the valve by the heater core was frozen so I replaced it with a standard 1/2 inch ball valve with 1/2 inch brass nipple pipe that fit the hoses, I can access the valve thru the front defroster cover. I also blew out the heater core fins with a compressor and vacuumed all the junk out, went to the engine compartment and opened the 2 valves behind engine on the driver side. One must be the feed and the other return. They opened very easily and no leaks. I then warmed up the 671 and topped off the antifreeze, bled air out of the heater core and bam, warm air to the front of the bus. Another win on the old 4104, love this thing, thanks for all the input.

[chessie4905]

That valve you removed is easily obtained at an auto parts store, btw.

[dtcerrato]

Extending just the handle of the valve as shown in one of the photos puts the handle in easy reach of the driver a very short distance from the right knee.

[Nel]

Dan , that's a nice set up but mine has been already revised by po's, so if that valve is closed I would think that will keep the hot water from flowing thru the core and kill any heat in the summer , do you keep the rear valves open all the time?

[Nel]

Dan , that's a nice set up but mine has been already revised by po's, so if that valve is closed I would think that will keep the hot water from flowing thru the core and kill any heat in the summer , do you keep the rear valves open all the time?