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Discussion Starter #1
Last week I finally replaced my radiator that had been leaking for a couple years. While I was in there I replaced the belt, tensioner, and a couple wheels. The week before I changed it I was losing a lot of coolant and losing heat at times. I thought I was losing heat because of the low coolant. After changing the radiator I’m still losing heat. Only losing heat on the highway about 20 minutes into my drive from my house. At this point the truck has been running 30 minutes. I don’t lose it till It gets to about 170° on the engine oil temp.

When I went into change the radiator I had a new thermostat. However, I did not change it for a few reasons. Do you think that’s why I’m losing heat? Bad thermostat?


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Did you fully bleed the system after the coolant change? Did you flush or backflush the engine with water a couple times as well? Did you use the correct oem coolant? If all of those were done properly my next guess would be thermostat personally.
 

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Did you fully bleed the system after the coolant change? Did you flush or backflush the engine with water a couple times as well? Did you use the correct oem coolant? If all of those were done properly my next guess would be thermostat personally.


I did not bleed the system. I didn’t know about having to do this. YouTube here I come!
I flushed it last year when I replaced hoses.
I did use the correct OEM coolant from ford.




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I would start with bleeding the system of air for sure. Those air pockets in the system always screw with stuff. I haven't done it on this truck, but prior vehicles you just keep the coolant bottle cap open and run the engine until it gets up to operating temp...preferably on an uphill incline slightly if possible. You'll see bubbles coming out the coolant bottle. Squeezing the upper/lower coolant hoses usually helps too. I'm sure you can find a youtube vid for doing it on these trucks.
 

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I would start with bleeding the system of air for sure. Those air pockets in the system always screw with stuff. I haven't done it on this truck, but prior vehicles you just keep the coolant bottle cap open and run the engine until it gets up to operating temp...preferably on an uphill incline slightly if possible. You'll see bubbles coming out the coolant bottle. Squeezing the upper/lower coolant hoses usually helps too. I'm sure you can find a youtube vid for doing it on these trucks.


I did this and had lots of bubbles coming back into the degas bottle. Hopefully this helps I wasn’t able to test it out after

Thank you for your help!


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Does the truck get up to around 195* ect and stay there? If not, its most likely a combination of bad tstat and air pockets... I would be willing to bet you have a big air pocket either way. Only way to really get all the air out is by using an air lift tool.
 

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Simple tests.. feel your heater core hoses.....If there both warm your good. Well one should be slightly warmer (inlet) than the other (outlet) If there both the same temp it’s plugged. But since you have heat I assume it’s not.
But if there cold then you have an air pocket or low coolant! The heater core is the highest point in a cooling system. Air rises. If there’s air. That’s where it will go. As you throttle up the water pump will push SOME coolant through it but not a steady flow as when it settles air will rise back up. So that’s a check to see if there’s an air bubble or bad heater core (or blown HG)-explained below

Second
If a thermostats bad as you drive temp goes down. You’ll actually watch your temp gauge drop. You can check that by feeling the upper radiator hose. On a cold start (if it’s stuck open) feel the hose if it’s warm right away you have a bad thermostat.
As the thermostat opens it’s allowing fluid through the radiator and while you drive cold air is cooling the coolant and the temp goes down.
Again you would see the gauge drop.

So if gauge isn’t dropping and stays steady.
Upper rad hose isn’t hot right away cold start
And your heater core lines are cold

YOU PROBABLY HAVE AIR. Or a bad head gasket. Head gasket pressure can blow a radiator apart and since diesel compression is so high the head gasket leak is pushing combustion pressure into the cooling system..again air rises...heater core is the first place it’ll go. And you’ll lose heat.

I have severely blown gaskets or cracked block I have ZERO heat and haven’t had it all winter lol
Goodluck!


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Discussion Starter #9
Must have been air in the system. 2 weeks of driving and not an issue. Thank you all for your help!


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