2.5L ('98-'01) Overheating and no hot air in cab AND...

[Ronq]

Have several things occurring. 99 2.5 sons truck not mine... over heating...replaced thermostat. Filled it with tap water brought it up to temperature just to clean it out a bit will drain and put proper antifreeze in it...the "other" occurrence is inside the cab he has no hot air blowing just cool air...sooo...no matter what position the switch is in (besides off) I can hear the AC clutch cycling??? I understand the lack of hot air in the cab may be because of the actuators in the dash not working properly...right?? And the AC cycling maybe the control switch...right??
Soo...all that being said where do I start??? Help please.

 

[Uncle Gump]

Start by ensuring you don't have trapped air in the cooling system...

The heater core is the highest point of the cooling system... if the system is low you will NOT have heat.

The A/C clutch should cycle as long as you have the controls on Heat or A/C. It's done to actually dry the air before blowing it into the cab.

 

[RonD]

Remove 1 heater hose at the firewall
THEN refill at rad cap opening
This lets the air out of engine from behind thermostat

When water/coolant start to come out BOTH the heater core outlet AND its hose, put hose back on, air is out
Do this anytime you are refilling a cooling system

Overheating and losing the heater can mean blown head gasket or cracked head
Also over filled overflow tank, and white exhaust "smoke"
If head gasket loses its seal the air/exhaust from that cylinder is PUMPED into the cooling system, at 1,000psi pressure
This displaces the coolant in the head and pushes it out to overflow tank, this causes the overheating part, no coolant in head
And some of that "air" gets into heater hoses which forms an "air dam" and blocks coolant flow thru the core
Water pump can only pump fluid, not air, so it can't push the air out, and no heater

 

[jack frost]

there is a test kit at oriellys to check leaking head gasket or crack in block...do you have a heater control valve between water pump and heater core