So I have been troubleshooting a few cooling issues and I am currently at a loss of WTF is going on with this thing.

The truck is a 99 5.4L SD and has no heat and was burping a little coolant.

The truck was originally burping coolant out of the overflow tank. After verifying that it was not a head gasket by all means except the exhaust gas test. I replaced the overflow tank and cap.

Now the truck is holding pressure fine but I do not have heat.

Here is what I have done:

I replaced the blend door actuator--no heat

I went to flush the heater core and since the quick disconnects were such a bitch to get off I decided ti replace it while I was at it. --still no heat,

New thermostat 195 deg --no heat

The radiator is brand new

Supposedly the water pump was replaced by the previous owner I have all the receipts for the truck so I could double check

Truck seems to circulate coolant fine i measured temps at the water outlet with an IR thermometer peaking at about 175~10 deg due to accuracy of the thermometer and heat loss due to thermal variations the lower radiator hose and reservoir coolant temps were around 76~10 degrees so the radiator is working as advertised

Truck doesn't overheat, granted after draining and replacing the coolant the temp gauge did climb some while driving until i worked out all the air pockets but still didn't overheat.

so at this point I am completely out of ideas. anyone have any.

Thanks

 

when you replaced heater core, I will assume you replaced the heater hoses. Did you transfer the restrictor to the new hose?

 

Sounds to me like you have a blockage somewhere. With the truck warmed up and the heater on high, feel the upper and lower heater hoses. Is one cooler than the other?

 

I did not replace the heater core hoses they were in good shape, I just removed the press fitting (very carefully) and replaced them with screw type clamps and yes the factory restrictor is still in place it looks like it is actually built into the hose.

 

It would seem that way but its a brand new heater core so i know that is not the source of the blockage. other than that I dont really know where it could be blocked.

 

I'm not trying to figure if the heater core is blocked, but rather to establish whether or not coolant is flowing to it. If one hose is warmer than the other with the blower on, you should have heat. If both are hot, you have coolant but no airflow to the core. If both are cool, something is obstructing flow to the core.

 

I just went through a similar deal. Not saying you did it but I let the most stupid and simple thing go un-noticed. I was 1.5 gallons low. I was chasing what I thought were air pockets. When I finally started adding coolant the level just kept dropping.

 

from what I could tell both core hoses were warm but not hot, I was quite frustrated when I checked them at that point. I will go ahead and check them again tomorrow.

 

hell at this point anythings possible, It looked as if it was full but I could have some air trapped somewhere in there Ill give the hoses a good squeeze in the morning and see if the level dropped.

 

Heard of a few of these water pumps that have had the impeller come apart or corrode almost completely away, I would definitely check to make sure it has been replaced.

When refilling the coolant remove the temp sensor from the top, front of the intake, that allows almost all trapped air to escape. Fill the system with coolant until it comes out the hole then thread the sensor back in and top off the coolant. The 6.8 in the F250 is even easier as it has a heater hose at the front of the intake with a small capped port on the hose fitting that I use to bleed the air. I have never had trouble with air trapped in the system. I've owned both since new, the truck is a 2000 and the van an 03, probably changed coolant 4-5 times in each, this works every time. I use a vacuum fill system for other troublesome cooling systems but these vehicles have never been a problem.

 

I am hoping it isn't the water pump as it was supposedly replaced but i am sure it is possible as its the only thing left in the system really. Interesting about removing the temp sensor, I am definitely going to try that. I have to drain the distilled water out of the system anyways since i flushed all the old coolant out. Right now its raining like crazy so hopefully I get a chance to do all this today.

 

Just changed my radiator... was easy with no air in system that I could tell. drove it and added to full cold mark..some vehicles are a bear but the 5.4 wasn't bad.

 

yea i really want to get out there and drain the distilled water out of the system try and properly fill it and put this one to bed but it has been raining here non stop. I hate this weather

 

When adding coolant to our side by side (Polaris rzr)we have to either bleed the system "or" park facing up hill so the air works towards the radiator. No idea if this works on a truck.
Silly question but if everything seems good but you get no heat are you sure the dash dial is even working? It might not be sending the signal to blow heat.

 

UPDATE: So I was able to drain the water from the system flush and fill up with coolant. I filled to the "fill" mark on the aftermarket reservoir. drove the truck around a bit.

as the temp started to rise i tried the heat....nothing still cold. I flogged it a bit...nothing...cold, meanwhile the temp gauge bobbled up and down a bit working air out of the system never getting past the half way mark on the gauge. when I parked the truck the coolant was down below the fill line (as to be expected since it was more than likely working air out) STILL NO HEAT WTF. I checked the heater hoses they were barely warm. upper radiator hose was warm ...not hot, at this point I am about to light this thing on fire.

for S's and G's I checked the blend ****, it was fine. at this point i topped it off to the fill line and called it a night.