MC5B- Main heater electric control valve

[artvonne]

  I got the bus winterized and ran it to mix and circulate coolant, but cannot get flow through the main heater core. I have cab heat and the radiators warmed up, but not the main heating circuit. There is an electric control valve, lower right side of engine, just forward of the gate valve on the return line. Both gate valves are open but no flow. I can feel heat up to the electrovalve, valve is cold as well as line going forward. I have power to the valve, so I removed the top bolt and slipped off what appears to be basically an electro magnet, leaving the remaining valve with a approx 5/8 inch post sticking up from the valve.

  I assume the electromagnet either pulls or pushes something internally, or rotates it, but in any case nothing is happening. I dont see anything I can do manually, and I really dont want to remove the valve if I dont have to. Does anyone know the valve im speaking of, and know of any way to open it manually??

  Or should I just bypass it?

 

   

[lostagain]

Personally, I would get rid of the electric solenoid valve and have manual valves only. Turning them on or off can always wait for the next stop. Sorry, I can't help you with the electric valve for now.

JC

[Rick 74 MC-8]

If your 5 is like most mci's defalt is open with no power. Try removing th wire

         Rick 74 MC-8

[artvonne]

  I quit for the night, ill play with it tomorrow. There was a lil bit of green to it, and its only going to 29F tonight, I should be okay. I'll try pulling the wire tomorrow and see what happens, if not ill bypass it and figure it out another day.

 

[Ed Hackenbruch]

Our low last nite was 74, tonite will be about the same.

[artvonne]

  74 is nice. But everything is a compromise, and there are other things to consider.

[bevans6]

default is open if no power to the valve.  I have a manual valve as well. The manual valve on the return is right there beside the electric valve, and there is one up behind the alternator.

Brian

[artvonne]

  Is there an air bleeder on the main heater core, or is it self bleeding? Ive decided I will just bypass the electrovalve for now and play around with it another day.

  Brian, I have gate valves on both lines as well, the one behind the EV and the other back behind the alternator. Both are open.

  Not exactly understanding why power is being applied to the EV to keep it closed when im calling for heat, but I can play with that another day as well.

[Rick 74 MC-8]

On my MC-8 the po put a switch in on the wire to that valve  comes in handy. I can turn heat full on if needed exe; getting ready to pull over for the night I can get it real warm to last b4 aux heat is needed. Or when pulling a big hill if temp starts rising it will bring temp rite down. And to answer your question yes there is a  bleader on the main heater also on drivers heater core


         Rick 74 Mc-8

[bevans6]

I believe the feeds for both the main and drivers heat come from the same feed, which is the cross-over tubes from the back of the heads and up over the transmission.  The return for the main is the one with the valve you are fussing with, the return for the drivers is the one over the alternator.  Both the returns basically go to the bottom of the water pump, eventually.  Mine just has the wire disconnected to the heater.  I really do plan to see if it works some time, but for now if I want to close the flow I just close the hand valve.

Brian

[artvonne]

  Thanks for all the replies. While I was able to figure out a lot of this on my own, and and all information is greatly appreciated, ya'll are a good support group. I spent about two hours putzing with it, 38F today with a nice stiff breeze. It is going down to like 25F tonight so it was imperitive I get the heater circulating or it would likely been destroyed. Here is what I found and accomplished. 

  The return line from the main heater core is on the right side of the engine, large 1-1/2" line to the electrovalve (EV), then a large gate valve, then tees into the right radiator lower return going back to the pump.

  The feed line to the main heater core appears to be coming off that front crossover Brian mentioned, but I cant see behind the alternator to say for sure. There is a large gate valve there (left side behind alternator), that is the main heater feed valve.

  As far as I can determine, the cockpit heater feed line comes from a valve above the water pump at the back of the drivers side engine cylinder head. The return line tees into the left radiator lower return back to the pump. The bleeder is right on top of the cockpit heater core, accessed after removing the main access panel below the entrance door control handle.

  I did find a bleeder for the main core. Inside the front cargo bay, facing forward, you open the the central HVAC air filter access door, the heater core air bleed is on the top right side of the core as your looking in.

  I closed both main heat gate valves and removed the EV, and bypassed it. Once I pulled the EV hose connection on the core side, about a gallon or so of pure clean water came out, so im very happy I got this done today. Once the hose was in place I opened both valves, topped off the reservoir again, and it was time to light it.

  After dropping to 32F overnight last night, and only about 40F by the time I got the EV bypassed and topped off the reservoir, I was wondering how the engine would cold start. It does have a block heater, but not surprisingly its inop. So I said a lil Prayer, flipped the master to on, and like the dude in the right stuff, pushed the big button. What a non event, I bet she was running before she turned twice. In no time at all I had heat coming from both heaters, and why today I dont know, but now the air lock on the entrance door started working.

  I only put in 6 gallons of antifreeze, which, if the actual capacity is truly 16 gallons, I should good to -5F or so, which is fine for now at least. Its supposed to warm back up in a few days, and ill run it up to temp and try to get a hydrometer reading to see what I have protection wise, and if I should add more antifreeze.

  So now its brewski time. Yippeeeee!!!!