I have a 2002 4.7 and I just got done doing head gaskets about 2 weeks ago. I just found out the other day when I turned me rear heat on it doesn't get hot it gets warmer then the outside air but not by much. I looked over everything and I don't no. can anyone help me.

 

I think those have an electric auxiliary coolant pump near the passenger side of the firewall for the rear heat, it may have stopped working.

 

Cruiser:

When you refilled the cooling system after the repair, did you burp the cooling system correctly? If not, you might have air remaining in the system causing issues.

As also mentioned, your aux coolant pump might not be working. This is located on the passenger side fender well and usually the failure mode is to leak as opposed to quitting.

Check and see if the hoses to the rear core located on the underside of the passenger rear quarter panel are both hot.

Don

 

My 01 4.7 is doing sort of the same. It blows air.. no matter whether its on hot or cold.. the air blowing out is neutral. Not hot.. not cold.. warm. outside air temp or a tad warmer. Think i'll look into these solutions also.

 

is this the heat at the very back if you search more you will find people talking about a blend door failure. something about a tab breaking off so it cant move. some people say the pump is not really needed to make it work and it will work just fine with the pump removed from the system.

 

this is the operating parameters of the electric coolant pump, it will not help prevent the truck from overheating, it does not run during normal driving, it is unlikely to be your problem unless you have heat while the truck is driving down the road and it disappears when you stop.