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Old 04-05-2021, 12:29 PM   #1
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Help: Identifying Coolant Intake and Return Valves for removing heaters

OK, I'm in need of some help. We have gotten to the stage of our demo where we are removing the 3 rear heaters. I know I need to shut off the intake and return valves for the coolant but...I am new to this and not entirely sure how to identify where these are. I *believe* I have identified the intake (going TO the heaters, my terminology is probably off) but I can't find the return (going back to the radiator?) valve.

We have a 1997 TC2000 Cummins 5.9 RE.

And yes, if anything I wrote reveals my ignorance, I am well aware that I am underqualified for this. I've looked at schematics and the users manual to no avail.

Can anyone help my identify (1) if I found the correct intake valve and (2) where the return valve is? Any help is appreciated!


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Old 04-05-2021, 01:43 PM   #2
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On my bus, there is a valve at the rear of the motor head. That feeds the heaters. Under the bus, next to the entrance way stairs, is the other valve. My bus has a big hose coming from the radiator bottom (at the front of the bus) to a black box just next to the motor. The heater hose loop enters this black box also, and there is the valve. The black box also has transmission lines going in/out, to cool the transmission fluid using the engine coolant after the radiator cools it.


Many folks here recommend (including me) you keep your interior heaters, even if you move/relocate them. I would definitely replace all the heater hose in that case; you don't want a leak into your new "house"
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Old 04-05-2021, 02:04 PM   #3
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Ignorance isn't a problem. You're on a good path of researching and verifying.

The absolute best way to identify your supply and return heater lines is to follow them from the heaters back to the engine.

From there, you'll find your valves.

Before disconnecting anything, close each valve, then start the engine and watch your temperature. If it's okay, and the bus is drivable, take her for a spin to get the engine to running temp.

If all is good, then you should be good to remove the heaters and hoses.

Even if you don't think you'll reuse them, hold onto them. Many of us change our minds. Also hold onto any clamps and connectors.

Make sure to save a piece of heater hose to identify the size and type of replacement hose.

Replacement hose comes in many specifications. If you want my input on my choice, PM me.

Best of luck.
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Old 04-05-2021, 10:56 PM   #4
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Before disconnecting anything, close each valve, then start the engine and watch your temperature. If it's okay, and the bus is drivable, take her for a spin to get the engine to running temp.

If all is good, then you should be good to remove the heaters and hoses.
.
I have been wondering about this. I'm pretty sure Coolant needs to circulate through the motor at all times, even while warming up, even if not through the radiator or heater cores. Therefore, you should not close the valves and drive, I think. I have been meaning to contact the Cummins dealer and ask this question specifically, because it sure would make things cooler in the summer if hot coolant wasn't circulating through the heater cores.


Instead, if I'm correct about needing to circulate, you should loop the coolant lines together if you remove the heater cores.


Remember, also: you need the heater core in the dash to help with condensation on the window, if you don't have dash A/C. A/C will pull the moisture out of the air and help dry the window faster, but otherwise, hot air will warm the window to the point that the moisture evaporates even into high-humidity when raining.


In my bus, it goes from the back of the motor head, to the dash heater core next to the entrance way stairs, then down under the front of the motor, and then back to the driver's foot heater, then back to the rear-wall heater, then back the same path, back under the motor, to the tranny cooler box.
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Old 04-05-2021, 11:15 PM   #5
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Quote:
Originally Posted by MeganMargoFox View Post

Can anyone help my identify (1) if I found the correct intake valve and (2) where the return valve is? Any help is appreciated!

While the removal of the heaters is definitely a subject of debate, I don't believe this is the actual heater shut off. It looks like it necks down too far to be a heater line, unless someone put a tee after the valve, and just added fittings to cap off the unneeded port. Not best practice, but sometimes you gotta do what you gotta do to make things work.

While this is definitely a valve, I get the impression that this is actually part of an auxiliary transmission cooler. Double check where all those lines go coming off of that box by following them as far as you can.

Your heaters are probably all routed down the driver's side, the water shutoffs, if installed, should be in the left side of the engine compartment or just underneath the floor on that side. They may also be on the engine block itself.
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Old 04-05-2021, 11:20 PM   #6
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The port poking down from the air tank above appears to be the air tank safety blow-off valve. Another angle / perspective would be better for confirmation, but since your air tank appears to be above, it could possibly be the air tank drain valve (necessary to remove moisture that accumulates in the tank -- required periodically -- DOT regs say once a day, I say once a week under fairly regular use, or before / after any single outing, whichever applies). Haven't seen one that looks like that before though.
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Old 04-05-2021, 11:41 PM   #7
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While the removal of the heaters is definitely a subject of debate, I don't believe this is the actual heater shut off. It looks like it necks down too far to be a heater line, unless someone put a tee after the valve, and just added fittings to cap off the unneeded port. Not best practice, but sometimes you gotta do what you gotta do to make things work.

While this is definitely a valve, I get the impression that this is actually part of an auxiliary transmission cooler. Double check where all those lines go coming off of that box by following them as far as you can.


I think there IS a "T" there - just to the right of the valve is the rectangular "T" block, and you can see the hose coming off of it, opposite the camera view.


That DOES look like where the heater hose goes into the tranny cooler on my bus.


At the far right of the "T" block, it shrinks, and I bet there is an air-bleeder line that goes up from there (to the reservoir?), but that is a guess.
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Old 04-06-2021, 12:26 AM   #8
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Originally Posted by Mountain Gnome View Post
I have been wondering about this. I'm pretty sure Coolant needs to circulate through the motor at all times, even while warming up, even if not through the radiator or heater cores. Therefore, you should not close the valves and drive, I think.
Totally agree that coolant needs to circulate through the motor at all times.

On my rear engine bus there are two valves, one is the supply line to the heaters and the other is the return line. When I turn these valves off the engine coolant system remains fully intact. This way if there is a leak in a heater line or one of the heaters you can stop the leak and still keep the engine running.

Since OP has a rear engine bus, I'm imagine her heating system is set up with the similar setup.

While I've removed the rear and mid heater, I am keeping the front heater and defroster for the driver's area. If needed, I will supplement heat with my vented propane furnace towards the rear of the bus.

My biggest concern with connecting the engine to the front heater was where to run my lines. My whole point of decommissioning the rear mid heaters was to reduce the potential for hose or heater leaks inside the bus. So, I'm going to be running the heater lines over the frame cross members up to the front heater / defroster.
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Old 04-06-2021, 11:11 AM   #9
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I was just thinking that, yet again, my brain failed to connect "A" with "B". And I was writing about both in the same post...


Even if the coolant needs to circulate, it won't on my bus because the heater return feeds into the radiator return at the tranny cooler box, downstream of the thermostat. It won't circulate until the thermostat opens.


I'm used to dealing with gasoline motors in cars, where the heater circuit feeds back into the motor.


Aloha!
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Old 04-06-2021, 11:12 AM   #10
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I also missed the "RE" in the OP. I didn't even realize there was a TC2000 that was an RE bus. Sorry!
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Old 04-07-2021, 09:59 AM   #11
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Even if the coolant needs to circulate, it won't on my bus because the heater return feeds into the radiator return at the tranny cooler box, downstream of the thermostat. It won't circulate until the thermostat opens.
I must have COVID-brain or something. I've always been a bit ADHD (usually just ADD), but I really can't focus anymore and get spaced out walking across the room, and have brain fog quite often, these past 2.5 years. I had symptoms like COVID 3 or 4 years ago in Hawai'i. Laid out for a week, unable to eat or get out of bed, started in my lungs. Either that or it was vaping the honey oil some millennials shared with me at a festival I went to in one of those "legal" states (I never smoke that by myself, ever). It didn't get me high at all, but hell if I could focus after. People invented water-filtration pipes (hookahs, bongs) to remove the oil (and tar), why people go out of their way to vape it now is beyond me. I was in "party" mode, and though to try it once would be OK. I also slipped into depression the day after that vape, and never came out.
Anyways....



The thermostat controls the flow OUT of the motor, into the radiator. It will NOT block the circulation of coolant through the heater cores.


Therefore, I still question whether it would be wise to close the valves while the motor is running. The cylinder sleeves and the exhaust valves get much hotter than the rest of the block/head. The motor needs to warm up "evenly". The circulating coolant prevents things from warping while everything heats up. If it doesn't circulate, the water could boil at those surfaces mentioned, while the thermostat stays relatively cool and closed.


I "guess" that the TCRE has a Cummins 8.3, and maybe that is different. But I wouldn't close my valves on my 5.9 without Cummins' blessing.


Aloha!
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