Air bleeder on dash heater core

lostagain · February 05, 2014, 12:01:26 PM

I drained all the coolant out my MC5's system to replace it with new antifreeze. I am hoping that the front heater core doesn't get air locked. But if it does, I'll have to access the heater core. Would be easy, except that the original converters covered the whole dash with upholstered plywood with no apparent screws to easily remove it. I think the heater core is between the driver and the top of the stair well, am I correct? Is there in fact an air bleeder valve on top of it? I'll have to peel the vinyl off to find the screws, or cut a hole to access the bleeder valve. Does anyone know where is that valve located? Would anyone have a picture of that area with the front panel removed? I think MC5, 7, 8, and 9 models would be the same.

In the past, every time I drained the coolant, I shut the valves to the heaters right in the engine compartment, so I didn't have to worry about air locks when refilling. I am hoping to get lucky, because the surge tank is higher than anything else. But there are bends and ups and downs in the piping that might trap air.

JC

luvrbus · February 05, 2014, 01:39:01 PM

There should be a plug on the temperature control if yours is original that is were I would bleed my 8 they will also bleed if break the heater line on the right side that is what I would do before tearing the dash out to reach the valve

bevans6 · February 05, 2014, 03:09:58 PM

The top of the heater core up front is higher than it's supply and return piping so it will air-lock. Only way to get the air out is to bleed it or wait a really long time for it to mix with the coolant (forget what that process is called) and come out that way. I don't know how much air will be trapped, thinking on it, it might be a lot. Now, there might be another way. I have, in the past, vacuum-bled tough cooling systems. You could fill the system, add a tee on the heater return line, use a tube to raise that higher than the level of the front heater core and put your shop vac on it to suck the coolant and air through the heater core.

Brian

Ed Hackenbruch · February 05, 2014, 07:14:49 PM

JC, i would imagine that your C is like my A. There is a little bleeder screw on the top of the heater core and the location of the core is where you think it is. I would bet that if you poke around a little you will find that there is a way to remove the paneling without ruining it. Maybe it is velcro-ed in place? Maybe magnets? Maybe he used clips like cars use?

Ed Hackenbruch · February 05, 2014, 07:18:05 PM

By the way you won't have to run the engine to get the air out.....open the bleeder screw and you will know when the air is out when you start getting anti-freeze coming out.

Dave5Cs · February 05, 2014, 09:53:37 PM

JC my bleeder valve on my 5C has one on top of the radiator/ heater core under center of dash. The middle panel has 2 1/4 turn bolts with slots at about 1/4 " down and in from the top corners. Turn them and when they let loose just pull up on the panel and it will come out. Unless like ed said someone has done something non original to it.

lostagain · February 06, 2014, 07:13:18 AM

Thanks guys. It would be easy if the conversion company didn't cover the whole front dash area with plywood that has foam then vinyl Naugahyde type material on it. Looks like I will have to peel the vinyl off to find the fasteners/screws. Or cut a hole and then patch it up after, or better, build a little door so I can get in there again. Or redo the whole thing in a practical way.

Although it looks nice, I still would prefer a bus that has been left alone in stock form. Or at least you would think they could have made it easier to disassemble. One of these days, I might have a leaky heater core and really have to open it up.

I talked to Taibob (Bob) from Oliver, BC, last night, who has a MC9 with the dash area opened up right now. He is sending me a picture this morning.

I'll look into it some more today. Have to stoke the fire in the shop first: -28C this morning. No mosquitoes.

JC

lostagain · February 06, 2014, 12:02:57 PM

All is good now! I was able to remove a piece of plywood above the stair well. Behind it is the metal panel (with grill in middle of it), that comes off easily with the two 1/4 turn screws. There is a bleed valve on top of the heater core. I got antifreeze out of it. But to be safe, I am building a little door in front of it for easy access for if/when I need to bleed again. Thanks everyone for the help.

JC

Larry B · February 10, 2014, 07:10:16 PM

Hello JC,, That metal door (the one with the grill in middle ) is how the air gets in to the heater and defroster core. If your heater seems to have a low air flow you might have to leave part of the grill uncovered to get better flow.
Larry B

lostagain · February 11, 2014, 06:29:27 AM

Larry, that grill is still exposed: the converters left an opening for it. It does get covered up when the stair well cover/passenger foot rest is up against it. The heater/defroster works just as well with it covered up; I find there is enough leakage all around the dash to allow enough air to get to the heater core. Air intake for the heater core is through that front grill in the recirculated position. It comes from the front of the bus in the fresh air position. The door to control that is cable operated by the handle to the left of the driver under the dash. The front A/C evaporator was right behind that grill (mine was removed). The grill was important to allow enough air for the evaporator mostly.

I would not have known all that a few days ago... I don't learn stuff unless I have to...

JC

Ed Hackenbruch · February 11, 2014, 01:31:40 PM

And in a few days you will probably have forgotten all of it!

lostagain · February 11, 2014, 06:01:47 PM

LOL Ed, isn't that the truth.

JC