Draining the coolant on a MCI 102a3

[paul102a3]

My book has directions for draining the coolant from the entire system (heating loop and engine) or the engine only.

I need to check and maybe drain the coolant in the heating loop only.

The PO replaced the coolant in the engine a few months before he sold the bus but can't remember if the heating loop was closed off with the gate valves when he did it. The gate valves have been closed since my purchase of the bus this spring.

I would hate to open the gate valves and contaminate the new coolant with old stuff.

Anyone know if I can just drain the heating loop and if so, how do I do it?

Thanks,

Paul

[Hartley]

You may need to remove the lower hose (before) the valve ( the lower valve )
( that would be to the right side of the valve. ) sorry.

Then once that is open, go up front and open the purge valve on top of the
dash heater core. Make sure the heat control valve is open (on).

If you have the factory air, There should be a purge vent valve somewhere near the top of the heater core. Or maybe the heat control solenoid unit.

That's all I got...

[buswarrior]

What is wrong with the "old" coolant?

The defroster core will drain, as it is above the pipes, the heater core will not, it is below the pipes. You'd have to drain it via it's own drain, one side of the core or the other, if you can get at it.

You will then have to chase the air out of the defroster core when re-filling.

If the system was just being re-filled to rotate the coolant, just open them up and let it flow?

If it was contaminated, wouldn't the PO have flushed it all?

This sounds like a lot of time that you may use profitably on other busnut jobs?

happy coaching!
buswarrior

[paul102a3]

Buswarrior,

The PO kept every record of outside work completed to the bus while it was in his possesion which was good. He did not keep records of work done by himself; not so good. He has no recollection of what he did or how he did the coolant change other than he had to go get a second case of coolant.

I did have the engine coolant tested and it is in good condition. I am reluctant to open the valves and mix who knows what into the good engine coolant. For all I know, the coolant in the heating loop could be many years old, incompatible with the newer coolants, etc.

I would hate to have to replace all the coolant because I opened the valves without checking.

I was hoping there was a drain somewhere in the heating loop or a hose that would be easy to disconnect so I could pull a sample to at least see if it was red, yellow or green. If the coolant was yellow or green, I would know that the heating loop was closed when the engine coolant was changed. If it was red I at least have a little more confidence that the loop was open when the PO did the change.

I may try to release the hose clamp on the heating loop side of the lower gate valve and see if I can get some coolant to drip.

Thanks,

Paul