Heat issue

[Bamfster]

Ok guys, i'm stumped.

01 Exp XLT w/ manual hvac controls

It used to blow nice hot air (last winter). AC worked with out a hitch all summer, and still does. With the cool weather recently I've needed heat. Now out of the blue it gets no where as hot as it used to. If I leave the blower off for a bit, when I first turn it on it blows hot for about 45 seconds but cools down again.

I already flushed and serviced the cooling system ... new rad cap and thermostat (195*) ... still no heat. The old coolant wasn't overly nasty. Temp gauge sits where it normally does.

I checked both front and rear blend door actuators and they are working fine. I cut the hole behind the glove box to inspect the blend door and it is functioning perfectly. Still no consistent heat ...

What now guys, help me out please

 

[stamp11127]

Restrictor and or heater core is mostly plugged. Disconnect the heater hoses and back flush both front and rear cores.

 

[Bamfster]

Restrictor and or heater core is mostly plugged. Disconnect the heater hoses and back flush both front and rear cores.

I did that already, it moves water and air thru the core easily. From the dash side, heat core is getting up to 188 as read with a temp gun (I drilled a hole behind glove box). Rear core is slightly cooler @ 171

 

[stamp11127]

Check the flow rate into and out of the core with the engine running. Use a hose and route it back to the surge tank. You only need to watch the flow for a few seconds once the t-stat opens.

 

[Bamfster]

Based on the temp of the heater cores, I would say flow is fine. But, on the off chance something is plugged, what type of flow should I be looking for?