Heater now doesnt work after flush

eiorg9 · Feb 18, 2015

For all you 6.4 geniuses out there i have a question and need a little help. Ok so i had originally had a little hole on my radiator and i decided to replace it. So i bought a Mishimoto radiator and i updated the Rad hoses and installed it. But, before i did the instillation i thought that since i had rust in my cooling sysytem, i wanted to flush it out and clean everything. So for 2 days i did flushes and everything was doing great. I then broke everything down and installed the new Radiator. Put everything back together again with the new Rad and checked for leaks, which there were none. Then when i started to drive it i decided to just use Distilled water until i was sure all the crap and rust was out of the system before i put in the Ford Gold radiator fluid. So once i got everything back together again and took it for a spin, i now dont have heat. Im pretty sure the heater core is clogged and im probably going to have to pull the dash and put in a new heater core but i just wanted to check on here to see if any one else has had an issue like this or not. With the hood up and the engine running it seemed like the Rad hose coming from the thermostats was shaking and almost burping. Also a few days before the new RAD install, i installed an EGR delete kit. My truck has 160,000 and everything has been ACES so ive been really lucky with my 6.4. But now i need a little help. I dont know if i should try to flush it again or if i have clogged something other than the heater core like the oil cooler bc i know those 2 are the weak spots. Anyhow i appreciate any info or responses that i can get.

sootie · Feb 18, 2015

what is your coolant temp. could be some crap in the system has stuck a thermostat open

eiorg9 · Feb 19, 2015

my temps are right around 210-215. Then it will spike to 230 and then come right back down to 215.

Mishimoto · Feb 19, 2015

eiorg9 said:
For all you 6.4 geniuses out there i have a question and need a little help. Ok so i had originally had a little hole on my radiator and i decided to replace it. So i bought a Mishimoto radiator and i updated the Rad hoses and installed it. But, before i did the instillation i thought that since i had rust in my cooling sysytem, i wanted to flush it out and clean everything. So for 2 days i did flushes and everything was doing great. I then broke everything down and installed the new Radiator. Put everything back together again with the new Rad and checked for leaks, which there were none. Then when i started to drive it i decided to just use Distilled water until i was sure all the crap and rust was out of the system before i put in the Ford Gold radiator fluid. So once i got everything back together again and took it for a spin, i now dont have heat. Im pretty sure the heater core is clogged and im probably going to have to pull the dash and put in a new heater core but i just wanted to check on here to see if any one else has had an issue like this or not. With the hood up and the engine running it seemed like the Rad hose coming from the thermostats was shaking and almost burping. Also a few days before the new RAD install, i installed an EGR delete kit. My truck has 160,000 and everything has been ACES so ive been really lucky with my 6.4. But now i need a little help. I dont know if i should try to flush it again or if i have clogged something other than the heater core like the oil cooler bc i know those 2 are the weak spots. Anyhow i appreciate any info or responses that i can get.

Sorry to hear about your issues! Are you positive that all air has been evacuated from the cooling system?

ckrueg · Feb 19, 2015

eiorg9 said:
my temps are right around 210-215. Then it will spike to 230 and then come right back down to 215.

Those Temps seem high. Is that just cruising empty? My coolant almost never goes above 200 unloaded.

2wd-fire · Feb 19, 2015

ckrueg said:
Those Temps seem high. Is that just cruising empty? My coolant almost never goes above 200 unloaded.

I agree my never gets over 196

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powerstroked08 · Feb 19, 2015

Same here 192-196 all day. Your temps are definately high if your unloaded(even when I hauled 31K I couldn't get mine over 215) Like mishimoto said make sure all of the air is out.

Delaware6.4 · Feb 26, 2015

Change your thermostats. Mine did the same thing but not after a flush. The seals broke down on one of mine causing the same issues. The flushing may have finished them off. Easy to do, not expensive. Worth a shot

powerstroked08 · Feb 26, 2015

Forgot about this, but my buddy and I did his radiator and got it all buttoned up and filled up. Truck ran great no leaks then it started getting warm when he would haul. So we thought there was air in the system. Come to find out one of the o rings was a little screwed up allowing it to pull in air when it was shut off and it was causing it to get hot. He replaced the hose with the updated one and all has been fine since.

Mishimoto · Feb 27, 2015

powerstroked08 said:
Forgot about this, but my buddy and I did his radiator and got it all buttoned up and filled up. Truck ran great no leaks then it started getting warm when he would haul. So we thought there was air in the system. Come to find out one of the o rings was a little screwed up allowing it to pull in air when it was shut off and it was causing it to get hot. He replaced the hose with the updated one and all has been fine since.

Yes, this is certainly a possibility as well. The original Ford radiator hoses utilized a single O-ring connection on both the engine-side of the hose and the radiator-side. During vehicle operation, the engine will move which caused flex of the hose. This flex allows air to enter the cooling system and is usually identifiable by coolant seepage on the exterior of the connection. Ford updated their hoses to utilize a double O-ring connection on the engine-side of the hose. Be sure these units have been updated.

Additionally, we currently have a pre-sale going for our silicone coolant hose kit. We developed CNC-machined quick-connect fittings with dual o-ring connections on both the engine and radiator side for extra protection against this well known issue.

Let us know what you find!

-John