Mike Romain

I have an older XJ so can't help with the valve plumbing, but can say to
check the run of the heater hoses. If they are above the level of the
coolant in the radiator, they can hold an air bubble and only let half
the flow to the heater core.

I have done and read about putting the Jeep's nose up on a bank and
filling it while it is running and sitting that way with the heater on
full. That can make the rad filler the highest point.

I found running a hose through the heater core also increased the heat.
A fair bit of crap came out of mine.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/in...?id=2120343242
(More Off Road album links at bottom of the view page)

WildWestAZ wrote:
>
> I'm troubleshooting a lukewarm heater problem and a couple questions
> have arisen which I haven't found answers to.
>
> First - the vacuum valves and heater slider flap (thing) under the dash
> all seem to be working correctly, just to make sure I also verified
> there are no climate control/vacuum leaks - connected a vacuum pump to
> the vacuum source line going into the Heater/AC unit from the line to
> the intake manifold & tank. I moved the climate control switch to each
> position and pumped up vacuum - the valve works for each and vacuum
> holds, good.
> I did notice that the heater valve is "off" (bypass) when the climate
> control switch is off, "on" (no heater core bypass) for all other
> positions (AC, Vent, Heat, Defrost, etc.), not sure if this is normal.
>
> Questions, any insight would be most appreciated:
>
> I have read where the heater can blow only lukewarm air in the cab if
> air is trapped in the core or hoses. Does anyone have suggestions on a
> good way to purge air from the heater lines/core?
>
> Can someone verify how the heater hoses are supposed to connect to the
> heater control valve under the hood? I bought the XJ used and it had a
> wrong valve installed, so I couldn't hook the (hopefully) new/correct
> one (from my local dealer) same as the old one. Mine is currently:
> With valve on side facing you, two parallel in vertical plane fittings
> on right side going to engine - upper to thermostat housing, lower to
> water pump, two fittings on left side at odd angles and down lower than
> the ones on the right - lower of these going to upper heater core tube,
> upper of these going to lower heater core tube. The main reason for
> this is - I bought all new factory hoses and valve, and with various
> fitting sizes (some 5/8, some 11/16) and hose angles, this
> configuration seemed to match up, but I haven't found a picture to see
> if I have them right.
>
> Can someone see if this is normal for the heater valve control from the
> climate control vacuum switch:
> Climate control switch in any other than in the Off position, vacuum
> applied to heater valve and sending hot water thru heater core.
> Climate control switch in Off position, vacuum removed from heater
> valve and bypassing the heater core.
>
> Thanks - KR

Mike Romain

I have an older XJ so can't help with the valve plumbing, but can say to
check the run of the heater hoses. If they are above the level of the
coolant in the radiator, they can hold an air bubble and only let half
the flow to the heater core.

I have done and read about putting the Jeep's nose up on a bank and
filling it while it is running and sitting that way with the heater on
full. That can make the rad filler the highest point.

I found running a hose through the heater core also increased the heat.
A fair bit of crap came out of mine.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/in...?id=2120343242
(More Off Road album links at bottom of the view page)

WildWestAZ wrote:
>
> I'm troubleshooting a lukewarm heater problem and a couple questions
> have arisen which I haven't found answers to.
>
> First - the vacuum valves and heater slider flap (thing) under the dash
> all seem to be working correctly, just to make sure I also verified
> there are no climate control/vacuum leaks - connected a vacuum pump to
> the vacuum source line going into the Heater/AC unit from the line to
> the intake manifold & tank. I moved the climate control switch to each
> position and pumped up vacuum - the valve works for each and vacuum
> holds, good.
> I did notice that the heater valve is "off" (bypass) when the climate
> control switch is off, "on" (no heater core bypass) for all other
> positions (AC, Vent, Heat, Defrost, etc.), not sure if this is normal.
>
> Questions, any insight would be most appreciated:
>
> I have read where the heater can blow only lukewarm air in the cab if
> air is trapped in the core or hoses. Does anyone have suggestions on a
> good way to purge air from the heater lines/core?
>
> Can someone verify how the heater hoses are supposed to connect to the
> heater control valve under the hood? I bought the XJ used and it had a
> wrong valve installed, so I couldn't hook the (hopefully) new/correct
> one (from my local dealer) same as the old one. Mine is currently:
> With valve on side facing you, two parallel in vertical plane fittings
> on right side going to engine - upper to thermostat housing, lower to
> water pump, two fittings on left side at odd angles and down lower than
> the ones on the right - lower of these going to upper heater core tube,
> upper of these going to lower heater core tube. The main reason for
> this is - I bought all new factory hoses and valve, and with various
> fitting sizes (some 5/8, some 11/16) and hose angles, this
> configuration seemed to match up, but I haven't found a picture to see
> if I have them right.
>
> Can someone see if this is normal for the heater valve control from the
> climate control vacuum switch:
> Climate control switch in any other than in the Off position, vacuum
> applied to heater valve and sending hot water thru heater core.
> Climate control switch in Off position, vacuum removed from heater
> valve and bypassing the heater core.
>
> Thanks - KR

Mike Romain

I have an older XJ so can't help with the valve plumbing, but can say to
check the run of the heater hoses. If they are above the level of the
coolant in the radiator, they can hold an air bubble and only let half
the flow to the heater core.

I have done and read about putting the Jeep's nose up on a bank and
filling it while it is running and sitting that way with the heater on
full. That can make the rad filler the highest point.

I found running a hose through the heater core also increased the heat.
A fair bit of crap came out of mine.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Aug./05 http://www.imagestation.com/album/in...?id=2120343242
(More Off Road album links at bottom of the view page)

WildWestAZ wrote:
>
> I'm troubleshooting a lukewarm heater problem and a couple questions
> have arisen which I haven't found answers to.
>
> First - the vacuum valves and heater slider flap (thing) under the dash
> all seem to be working correctly, just to make sure I also verified
> there are no climate control/vacuum leaks - connected a vacuum pump to
> the vacuum source line going into the Heater/AC unit from the line to
> the intake manifold & tank. I moved the climate control switch to each
> position and pumped up vacuum - the valve works for each and vacuum
> holds, good.
> I did notice that the heater valve is "off" (bypass) when the climate
> control switch is off, "on" (no heater core bypass) for all other
> positions (AC, Vent, Heat, Defrost, etc.), not sure if this is normal.
>
> Questions, any insight would be most appreciated:
>
> I have read where the heater can blow only lukewarm air in the cab if
> air is trapped in the core or hoses. Does anyone have suggestions on a
> good way to purge air from the heater lines/core?
>
> Can someone verify how the heater hoses are supposed to connect to the
> heater control valve under the hood? I bought the XJ used and it had a
> wrong valve installed, so I couldn't hook the (hopefully) new/correct
> one (from my local dealer) same as the old one. Mine is currently:
> With valve on side facing you, two parallel in vertical plane fittings
> on right side going to engine - upper to thermostat housing, lower to
> water pump, two fittings on left side at odd angles and down lower than
> the ones on the right - lower of these going to upper heater core tube,
> upper of these going to lower heater core tube. The main reason for
> this is - I bought all new factory hoses and valve, and with various
> fitting sizes (some 5/8, some 11/16) and hose angles, this
> configuration seemed to match up, but I haven't found a picture to see
> if I have them right.
>
> Can someone see if this is normal for the heater valve control from the
> climate control vacuum switch:
> Climate control switch in any other than in the Off position, vacuum
> applied to heater valve and sending hot water thru heater core.
> Climate control switch in Off position, vacuum removed from heater
> valve and bypassing the heater core.
>
> Thanks - KR