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Old 03-15-2016, 11:24 AM   #1
Bus Crazy
 
Join Date: Apr 2013
Location: Colorado
Posts: 1,402
Year: 1993
Coachwork: bluebird
Engine: 5.9 Cummins, Allison 545
Rated Cap: 2
coolant system valves

i've never thought too much about the red painted valves that i have on the cooling system.

turning one off seems to prevent hot air from from blowing through the dash in the summer time. when i bought my bus from a southern arizona school district, the coolant valve was closed. i figured out the purpose of the valve a few days later.

the other valve is on what the manual calls the transmission cooler. an odd shaped box under the bus.

then manual says that closing the 2 valves is for isolating the coolant system, nothing about comfort or operation of the cooling system.

could someone please explain the trans cooler to me? and whether or not the valves should be in the open position for operating?

i've never overheated, only run hot up a hill, normal hot. ive operated with the cab valve closed most of the time, to keep the inside cool in the summer time.

fyi i have a bluebird FE cummins 5.9
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Old 03-15-2016, 04:46 PM   #2
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Join Date: Jul 2011
Location: Winlcok, WA
Posts: 1,607
The valves shut water flow from the engine to the different heater cores.

Unlike in a car, when you turn on and off the heaters or defrosters all you are doing is turning on or off a fan/blower. You are not turning off the hot water that flows through the system. In hot weather the heat the radiates out of the heater and defroster cores can add measurably to the discomfort level that comes from driving around in a mobile greenhouse.

The valves just stop the circulation of coolant from the engine into the heater/defroster cores. The radiator was sized from the factory to be adequate for cooling the engine on a hot day while going up a grade with a full load.

Most transmission coolers I have seen look like an A/C condenser in front of the radiator. I have seen a few that have the transmission fluid going through a heat exchanger with the heat being transferred to engine coolant. It can look like a box with a coolant hose going in and another hose going out with the transmission fluid going in one end and out the other.

If your bus has a heat exchanger type of transmission cooler DO NOT ever close the coolant off to the heat exchanger. Not only can you overcook your transmission you run the real risk of boiling the coolant in the heat exchanger and blowing the heat exchanger up.
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Old 03-16-2016, 04:37 PM   #3
Bus Crazy
 
Join Date: Apr 2013
Location: Colorado
Posts: 1,402
Year: 1993
Coachwork: bluebird
Engine: 5.9 Cummins, Allison 545
Rated Cap: 2
this is what the manual identifies as the transmission cooler.



another view:

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Old 03-16-2016, 04:45 PM   #4
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Join Date: Jul 2011
Location: Winlcok, WA
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That definitely looks like a heat exchanger type of transmission cooler.

I would guess the wire at the 90* elbow is the sender for the transmission temperature gauge.

The only reason I could think of that you would ever close the coolant valve is if you had a leak somewhere in the line between the heat exchanger and the radiator and needed to isolate that part of the system to make the repair.
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