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Junior Member
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149 Posts
Discussion Starter #1
have a 2008 f350 crew cab with about 92,000miles on the truck I did a DPF delete and heat and everything worked fine. then a few weeks later I got around to doing the EGR delete and now for whatever reason the truck when at idle doesn't blow heat it blows cold until I step on the throttle and it will start getting warmer.

I'm at a loss as to what this is.

truck is completely stock besides DPF delete and EGR delete. just heat doesn't really work. let truck sit for 30mins with cap off to bleed out air but still no heat.

think maybe clogged heater core? also heard of weak thermostats being a cause. is there anyway it's headgaskets? (hope not)
 

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Senior Member
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1,324 Posts
Does it gave a vacuum actuated heater coolant valve like the 6.0? Maybe you disconnected it during the work. Sorry don't know much about the 6.4.
 

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Junior Member
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149 Posts
Discussion Starter #3
no vacuum valve like the 6.0

I'm thinking it's a partial clogged heater core

just curious if anyone else knew

I'm going to replace the degas bottle cap, thermostats, and back flush the heater core and hope it fixes the issue
 

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Junior Member
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33 Posts
We see a lot of no heat at idle issues with them due to coolant leveling just being to low. Hows your coolant level?
 

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149 Posts
Discussion Starter #5
it's good stays the same. not losing coolant so I don't think it's headgaskets. this all happened after the EGR delete. it did puke once when it was pulling a 14,000lb load but hasn't since then and has been towing heavy loads since then just fine.

have any pointers on how to easily flush the heater core on these trucks
 

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How does you Oil temp look? Maybe your oil cooler is plugged. Its highly recommend to replace your oil cooler when an egr cooler ruptures. Plugged oil coolers can cause these symptons that you are also seeing.
 

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Sorry didnt see you coolant flush question. There is really no fast or easier way. Why would you cut corners on something that costs so much money. I'd do it the right way. This is a write up from over at powerstroke.org

6.4 coolant flush process

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Flushing and Cleaning the 6.4

Parts Needed:

• 20+ gallons Distilled water (grocery store)
• ½ gallon RESTORE (local Cummins dealer)
• ½ gallon RESTORE PLUS (local Cummins dealer)
• 4 gallons ELC rated coolant (local big rig dealer)
• Thermostat set (Ford dealer)
• Updated radiator cap (Ford dealer)


1. Begin by draining as much coolant as possible. Do this by removing the lower radiator hose where it connects to the radiator. Also remove one or both drain plugs in the engine block (one on each side, passenger side is difficult to reach as it is behind the starter.
2. Remove the thermostats (located near the vertical EGR cooler) and replace the thermostat cover without the thermostats. This will allow for quicker circulation of coolant to aid in the cleaning process.
3. Put lower hose back on radiator and put the drain plug(s) back in the block.
4. Put heater controls on high to ensure that heater core gets flushed as well.
5. Fill system with tap water and let the truck run for 5 minutes to let water circulate. Drain system as stated in step 1.
6. Repeat step 5.
7. Add ½ gallon of RESTORE and fill system with tap water again. Let the truck run on high idle for 60-90 minutes (watch temperature!! Allow a little warmer than usual but nothing extreme). Drain system as stated in step one.
8. Flush 3 times as stated in step 5 with tap water.
9. Add ½ gallon of RESTORE PLUS and fill with tap water again. Let the truck run on high idle for 60-90 minutes (watch temperature!! Allow a little warmer than usual but nothing extreme). Drain system as stated in step one.
10. Flush as stated in step 5 with tap water until water comes out clear and clean.
11. Flush 3 more times using distilled water to take any tap water out of the system.
12. After draining the system from step 11, put in new thermostat set.
13. Fill system with 4 gallons of ELC rated concentrated coolant and top off with distilled water
14. Replace radiator reservoir cap with updated cap and check truck for leaks
15. Let truck run for 30 minutes while topping off with distilled water. Keep extra coolant/water with you for a while the air gets worked out of the system.
 

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Discussion Starter #8
not cutting corners meant what's the easiest way to back flush the heater core.
 

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33 Posts
The only thing you need to do to flush the heater core is when you are doing the flush make sure the heat is on full blast that gets the cleaners circulating through the heating part of the system.
 
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