heaterbox issues?

[JeepcoMJ]

ok, so I'm not getting alot of heat from my heater in the cherokee. neither is my dad with his comanche, or my brother with his. we've flushed the radiator systems, and I even removed the vacuum system from the input/output hoses going to the heater core (yes, I plugged the vacuum hose to that).

 

I'm wondering where it sucks air from. all of these trucks blow warm as hell air on a 40 degree day, but not much on colder days...leading me to think that it's got a sealing problem in the heater box.

 

after looking at the a/c box I have laying in the barn, I see that it has a cold air intake (the one that goes to the cowl), and a interior intake (see picture below)

 

when you put the heater controls in a/c HI, that interior intake opens, which blocks off the upper intake. supposedly that would suck in inside (cold) air only rather than a mix of outside and inside air.

 

it doesn't go into that position for any other position. why?

 

I figure this is probably a common problem. my comanche heats up like a mofo too so I'm thinking there must be a leakdown in the system where it's sucking in cold air...probably right where the heater core goes through the firewall.

[TNT]

That is only used for recirculating the air on Max A/C, in all other modes it uses outside air. Did you flush your heater core forward and backward, they tend to plug up. Also make sure your heater control is fully moving it's door. Sometimes the heater control valve in the heater hoses can be a problem also. It keeps hot coolant from entering the heater core on Max A/C and sometimes stick. They can be eliminated which will also improve coolant flow threw the heater core. Your A/C might not be as cold on Max A/C mode thats all.

 

I also found that a good thermostat like a Robertshaw which can also be boughten from Moroso will help is warm up quicker and maintain a constant temperature. They open and close fully within 2-3 degrees of the rating temperature.

[JeepcoMJ]

yep, removed the heater control valve, flushed both ways, came out clear...it's not plugged.

 

 

it blows cold when it's at idle, and warm-ish when it's at cruise.

[TNT]

yep, removed the heater control valve, flushed both ways, came out clear...it's not plugged.

 

 

it blows cold when it's at idle, and warm-ish when it's at cruise.

 

That sounds like there is an air pocket in the cooling system.

 

That also happens if the coolant is low(which I'm sure it's not.

 

Make sure your heater control valve is working. It could also be caused by low coolant flow from a waterpump having the vanes start rusting off and not moving enough coolant at idle.

[JeepcoMJ]

methinks I'll just put the brand new water pump off the other motor on this one...it's a free repair.

 

yes, probably an air pocket but I've bled the entire system. the upper rad. hose doesn't seem to have much coolant in it though (real squishy)...even though I've bled and re-bled it.

[TNT]

methinks I'll just put the brand new water pump off the other motor on this one...it's a free repair.

 

yes, probably an air pocket but I've bled the entire system. the upper rad. hose doesn't seem to have much coolant in it though (real squishy)...even though I've bled and re-bled it.

 

My radator cap is on the left side so I jack that side up as high as possible to get all the air out. If your cap is in the center jack the front end sky high.