Heater core bypass on a cab tractor??

[jay baker]

I have an XR4140 cab tractor and was thinking about bypassing the cab heater core. It gets pretty hot here in south Texas and the idea was to keep heat out of the roof of the cab. I don稚 want to block off the hoses, I want it to continue to circulate, as it probably goes to or from an egr cooler. Has anyone ever done this?
Thanks.

 

[buickanddeere]

Check instead of guessing . Don’t the heat controls vary the output by varying the coolant flow. If the factory valve is supposed to isolate but is seeping. Adding another valve to ensure zero flow will not damage anything.

 

[jay baker]

Check instead of guessing . Don’t the heat controls vary the output by varying the coolant flow. If the factory valve is supposed to isolate but is seeping. Adding another valve to ensure zero flow will not damage anything.

That’s not how the system works. The temp is adjusted thru a blend door in the hvac unit.

 

[buickanddeere]

That’s not how the system works. The temp is adjusted thru a blend door in the hvac unit.

Stop the coolant if the flow is not critical.

 

[SmurfOperator]

Stop the coolant if the flow is not critical.

There is an electronically controlled valve that stops the flow when the heater is turned off. If you open the roof cowling and have someone actuate the heater controls you can see the valve opening and closing. It is located just a couple inches away from where the coolant enters the roof so there shouldn't be any measurable heat gain in the cab with the heater shut off. The AC in these tractors typically blows ice cold, if you are getting to hot there is probably a malfunction in the system somewhere.

 

[PCABE5]

There is an electronically controlled valve that stops the flow when the heater is turned off. If you open the roof cowling and have someone actuate the heater controls you can see the valve opening and closing. It is located just a couple inches away from where the coolant enters the roof so there shouldn't be any measurable heat gain in the cab with the heater shut off. The AC in these tractors typically blows ice cold, if you are getting to hot there is probably a malfunction in the system somewhere.

Those actuators you see control blend doors that control air flow across the heater core. There are also actuators that control mode doors. The heater core always has coolant flow and you cannot simply shutoff the flow because part of the feed circuit is from the oil cooler. So if you did not want flow to the heater core you would have to install a bypass.

 

[SmurfOperator]

Those actuators you see control blend doors that control air flow across the heater core. There are also actuators that control mode doors. The heater core always has coolant flow and you cannot simply shutoff the flow because part of the feed circuit is from the oil cooler. So if you did not want flow to the heater core you would have to install a bypass.

Open your roof cowling and take a look. It may be a bypass and not just an on/off valve but its there. If your system is working correctly you will not have any coolant flow through the heater core when the heater is turned off.

 

[PCABE5]

Open your roof cowling and take a look. It may be a bypass and not just an on/off valve but its there. If your system is working correctly you will not have any coolant flow through the heater core when the heater is turned off.

I've had it open a few times. I think what you are looking at is on the right side there is a brass "H" tied into the heater hoses. Although it is termed as a bypass, more likely for a pressure, there is no mechanical on/off above that.

Looking at the parts diagram I do not see any means to shut off or bypass flow to the heater core.

 

[SmurfOperator]

I've had it open a few times. I think what you are looking at is on the right side there is a brass "H" tied into the heater hoses. Although it is termed as a bypass, more likely for a pressure, there is no mechanical on/off above that.

Looking at the parts diagram I do not see any means to shut off or bypass flow to the heater core.

Follow the heater lines past the brass H you will see there is a shut off valve just inside the air box. I have attached a couple pictures. Its deceiving because it is inside the air box and it is opened/closed by the same actuator that controls the air diverter.

 

[PCABE5]

Follow the heater lines past the brass H you will see there is a shut off valve just inside the air box. I have attached a couple pictures. Its deceiving because it is inside the air box and it is opened/closed by the same actuator that controls the air diverter.

Ok I kept looking at the parts drawing and it looks like a bleand door actuator, so I brought up that part number AND bam it is listed as a water valve. Must control both functions.

You deserve a beer and a Merry Christmas.