Bus Hydronic Heater Issue

[Henukaw]

One (of my many) blonde moments...

I went to install my stock floor heater today and after I finished I noticed that I may the hoses hooked up incorrectly. I spaced out to mark the lines when I removed them some months ago.

I am not aware if one line is supposed to go in one side (providing heat) and the other for the exiting coolant... or not. I was hoping that it did not matter where each line was hooked up. The bottom line I now know is the line that supplies the heated coolant as it got pretty warm as the bus warmed up. The other line remained freezing cold as well as the air the heater was sending out.

Tomorrow I am going to switch the lines around but I thought I may ask if this may be my problem.

 

[bansil]

It sounds like one of the valves in or near engine is shutoff not allowing coolant to flow,most buses have atleast two of these valves

 

[Henukaw]

That was another weird issue I had.

When I first removed the heater I also closed the two coolant valves going to/coming from the heaters. I placed the hose lines I removed from the heater in a 5 gallon bucket for the remaining coolant to pool into. I was only getting coolant coming out when I drove the bus. I expected it to be some remaining coolant from the lines. However... the coolant only seemed to come out as the bus warmed up and pressure built up in the lines. That would only happen if the lines were "open" to allow the flow of coolant. Yet... both valves were closed.... That boggled me.

I opened both valves yesterday and replaced the coolant that was removed when I took out the heater. I let the bus idle for a good 30 minutes as I waited for any change in the heater to warm up or what have ya... and nothing. I am going to play around with it today I see if I cannot find out my issue.

I first thought it did not matter what direction the lines went into and out of the heater... but I have a feeling there is a set "In and out" for it. I am also going to check the lines and see if there is not something going on with the flow somewhere.

 

[Henukaw]

Ah! Thanks. That's a great point... I didn't consider that when I was working on it yesterday.

I did hear what sounded like air being purged out when I kicked the heater on now that I think about it. I will check to see if there is in fact a bleeder valve on the heater and see if that changes anything.

 

[Henukaw]

I got it working.

I let the bus warm up pretty well and then turned the heater on high. It gurgled and I could hear air leaving the heater. As soon as the heated coolant ran through the unit it warmed up nicely and warmed the bus very well in a short amount of time.

Thanks again for the help folks! Now I can drive out of this cold infested area with a working heater. Woot woot!

 

[Elliot Naess]

The concept of which-hose-goes-where is that the hot water should go in at the top. This complies with the basic physics phenomenon of "thermo-siphon". Hot water rises, and as it gives off its heat it wants to sink. Same as the engine radiator.

Some buses have an electric pump to boost the heater flow. I noticed them on a shelf at my local Blue Bird dealer.

You can get fittings with a bleeder valve in them, to expel air during filling of the system. It's just a butt splice with a bleeder screw in the middle. My first bus had them, located at the highest points of the heater hoses.