MCI 102a3 Cabin Heat

[Doug1968]

I replaced the main heat water valve on my coach this morning. The PO had replaced the electric water control valve with a manual valve and there was no way to control the cabin heat. After the install I started the engine and let it run for about 15-20 minutes on fast idle to see how the heat system worked. It didn't warm up at all inside even though the temperature gauge was at 170 degrees. When feeling the valve i could not feel any warmth on the inlet or outlet. I assume that the reason for not getting any warm water to the valve is due to the thermostat not being warm enough to open?

While changing the water valve I thought a large amount of water would drain from the pipe but I only had about 1-1/2 gallons come out?

Can anyone tell me at what temperature the thermostat on a 8v92 would normally open? Does one have to get the engine working before the temperature gets high enough to open the thermostat?

Any thoughts on this would be greatly appreciated.

[gumpy]

Thermostats should open at about 185, but that has nothing to do with not getting heat to the front heater core and electronic valve.

Sounds like one or both of the valves in the engine compartment are shut off.

[Doug1968]

Grumpy,

I shut both the lower and the upper valves off when changing the main valve? Turned them both back on prior to starting the engine. Shouldn't I be able to feel some warmth at the main valve? I'm a little lost as to why I'm not getting any heat on either side of the valve.

Doug

[buswarrior]

the coolant for the heater circuit is not restricted by the thermostats.

If there is any warmth in the engine, you should have warmth in the heater pipes.

Keep searching, there's something still closed/blocked.

I am assuming you filled the system back up all the way and bled the air in all the right places?
Cross over pipe and the top of the motor towards the back, perhaps on the heater line?

happy coaching!
buswarrior

[gmpd4104]

I would say try to bleed the system.

second guess one of your gate valves failed and gate is close.  replace it with a ball valve

[Tenor]

Now I know that this is almost comparing apples to oranges, but my MCI 7 has a 3rd valve by the driver.  Did they keep something like that in the 102 series?  Also, if not bled right, you will not get heat.  My driver's heater core has a small fitting on top to bleed it out.  I'd expect that there is one there still in the 102 models.  Someone here must have experience with these busses.

Good Luck!

Glenn

[JackConrad]

Did you bleed the air out of the bleeder vavles on top of the main heater core in the front bay and the driver's heater core in the dash?  Jack

[Brian Diehl]

Doug,  When I first got my 96A3 I thought I could easily open the supply and return water valves in the engine compartment.  I *thought* I was opening the supply (right underneath the floor in the engine compartment) as the handle would turn a couple of times.  However, no heat!  I ended up unscrewing the valve apart and found the gate was "stuck" shut.  All I had been doing with the valve handle before was turning it within the slope of the gate connection (screw).  I ended up getting the gate unstuck and from then on I have had heat up front!  So, are you sure both your valves are open all the way?

[luvrbus]

I don't think he ever got the engine temp up enough to start circulation yet.He needs to find out what thermostats he has in the engine.My 8v92 will not circulate the water till it reaches the 185 on the thermostats its very unlikely he has 170 thermostats in 8v92 from the Northwest.    good luck

[Doug1968]

 Well, today I opened the vent on the main heater core once more to see if there was any trapped air and only coolant came out. I then started the engine and let it heat up to about 175 degrees and I checked the valve under the cabin floor and above the transmission and I found that the pipe in on the engine side of the valve was hot and on the other side of the valve it was cool to touch.

It appears as though I have the same situation that Brian encountered? I screwed the valve in/out a few times but the condition stayed the same. I now believe that the valve has failed shut or almost shut.

Now the question is how to replace the valve? The valve is soldered at both ends and the end toward the front is almost touching the cabin floor. I have done a lot of copper sweating but as you know once filled with water it can be difficult. Also, this is a very hard spot to get to?

The copper tube coming back towards the engine is about 8" long and then it gets clamped to a hose. The tube that runs forward runs down at 45 degrees for about 2-1/2" and then straightens out and runs against the cabin floor.

What do you guys think about me un-clamping the hose at the engine side of the valve and cutting the copper tube on the front close up against the valve and mounting a 1" copper body ball valve with a good quality 1" hose at both ends?

I will no doubt lose some coolant during the process but if I get the hose mounted to the closed valve and remove and replace with the new valve quickly it might not bee too bad. After hearing about the problems with air in the coolant and the engine issues that can develop, I don't want those problems.

Does this plan sound good or does someone have a better idea?

Thanks,

Doug

[busshawg]

I may not be very much help but nobody is jumping in. Do you exsiting valves had a hex cap on them. So that you can unscrew and pull the guts out of the valve? If so you probably wouldn't loose so much coolant as you would be able to plug it with a clean rag or something while you replace the rubbers in the valve, just a thought.

[Doug1968]

Busshawg,

Yes, the valve stem can be removed. I thought about taking the valve apart but I'm thinking that it might be that the gate has come loose from the stem? Possibly not, cause the valve stem does quit turning both when you turn it in and out?

Since this valve is old I may not be able to find parts for it. I'm wondering if changing it wouldn't be best then I know what I have? I've only had the coach since September and I plan on using it for several years so I probably better change it out.

Thanks,

Doug