Heater core/AC

[gflat65]

2002 expedition 5.4L CLT 4x4
Just posted about replacing the gear selector motor.

During the test drive after replacing the gear selector motor, I turned the AC on. It was nice and cold. Turned it off so I could hear the truck while driving. Stopped and restarted the truck, and drove a little more. Turned AC on, and a puff of haze shot from the dash, and the AC was putting out hot air. Switched to Panel, and the same. Windshield fogged up. My glasses fogged up.

I just replaced the heater core about two months ago. Real pain in the ass. It’s been doing great since then. I had started to smell antifreeze when I’d turn the panel on last weekend (only drive on weekends, moving from one state to another).

The floorboards are now wet, so I figure the heater core blew again. No signs of leaks in the engine compartment.

What would cause it to blow out do soon after being replaced? I flushed the system before putting the new core in. There was a small beach under the engine after flushing (looked like fine, redfish brown sand n the ground). Filled with RO/DI water and new coolant. It never ran hot, and there was generally a small amount of fluid in the tank degas tank.

 

[gflat65]

Anyone?

 

[Billme]

I would hook the heater hoses together and do a pressure test, to see if you have a blown head gasket.. You can do it cold, and then crank and warm up..
If that checks ok, then you need to check if you have high voltage in your cooling system..
I think there is a design problem with the cooling level which might leave an air gap in the heater core as well..

 

[Splicer1998]

2002 expedition 5.4L CLT 4x4
Filled with RO/DI water and new coolant. It never ran hot, and there was generally a small amount of fluid in the tank degas tank.

Which one did you use, RO (reverse osmosis) or DI (distilled)?
BIG difference between the two.

 

[gflat65]

Which one did you use, RO (reverse osmosis) or DI (distilled)?
BIG difference between the two.

It was RO/DI. I run salt water aquariums, so everything runs through an RO then DI canisters (de ionization cat ion/an ion mix) before use in the aquarium. Gives a TDS below 5, with heavy metals filtered out by the carbon block, sediment, and RO membrane.

I replaced the core on a weekend when a big storm was coming, so, of course, everyone went on a water/milk/bread run and cleaned every store within a 15 Mike radius out of distilled.

I did a search and it said that should be fine. But you know the interwebs…