01 with 160k. Runs great. Time for new antifreeze it's been 5 years. Time to replace original hoses, although still fine. Flushed cooling system with flushing mix with heater on. Drained system and replaced hoses. Added 3 gallons full strength antifreeze, topped off with 1 1/2 gallons water. Engine runs up to normal operating temp, but heater blows cool air. Drove truck 100 mile and no change. Outside air temp is 45. Any thoughts? Heater worked fine before.

 

I'd download the 01 FSM from pdftown & look up what allows coolant into the heater core. Even if you had air in the system, you should get some heat if the heater control valve was opening and the engine is hot.

 

You have vapour lock. If you notice, the heater core is, oddly enough, the highest point of the system. It can take a long time to get that part of the cooling system filled.

Make sure your rad is full, there is plenty of fluid in the overflow tank and you have a good rad cap. Get your truck up to full operating temps. It only fills from the overflow as the engine is cooling.

Another option is to put a tee in the heater hoses at the highest point. There are tee's that you can use to flush the system using a garden hose that fit on the heater hose. One of these will allow you to top up the heater core. That should speed up the process.

By the way, there is no valve on the heater core. Coolant flows through the heater no matter what the temp setting of the heater...summer, winter...it just doesn't matter.

 

Or, your water pump is going out.

 

I do have a flushing tee there. I will try to add coolant from that location. Thanks

 

JoeCanuck

great advice on the tee. I had to do that with my 95. when cold starting the truck I would hear the heater making a noise and I had poor heat. I installed a tee and started the truck and when it got hot I just cracked the tee a bit and got out all the air that was causing the problem. worked for me. later Don T

 

I'll give that a try. Thanks

 

Cracked the flushing tee to try to burp a possible air lock. Let it run for 5 minutes at cool temp and 5 minutes at operating temp. Coolant leaked out at a steady pace with no decearnable burp. Also noticed this morning after yesterdays work that the resiviour had lowered from the full mark to the low mark to replace the lost coolant. I don't think I have an air lock and probably need to consider a core problem? I am not positive it produced heat prior to the coolant change. Any thoughts?

 

make sure the blend door is moving. I know it sound really simple but did not know if you checked it. I have had to replace the blend door motor twice on mine. Just a thought...

 

The air flow moves to where the selector setting is set. Through the defrost when set there, through the dash when set there, blended when set there if that is the question all seems ok? Checked both heater hoses(and cracked both hoses) and both are hot to the touch when at operating temperature. I guess this means coolant is passing through the heater core? Still blowing cold air.

 

No I meant the blend door motor for the hot / cold air blend. Motor should be located by the trans hump on the passenger side. Turn key to run (no start) and move the switch for cold/hot and listen for the motor turning, you could unplug it and check voltage change at the plug if you want to be all technical about it...

 

Thanks for the reply. I will check this now.

 

I think Your right. I removed the glove box and radiator core is hot to the touch. The motor your talking about has 3 screws and a pigtail. I 've got two screws out and the 3rd is about 1/4 above the floor board. What is the best way to change out?

 

I took a prybar and just pryed it out then did not put it back in... not saying that is the best way but...

 

Sounds good to me.