Another cooling system question. Leaking only when heater on

[Joey c]

found a little info that sounded similar but not a real clear suspect yet. 03 v8. Just got it about 2 months ago. Replaced upper radiator hose, split at plastic seam. Then the tstat housing. Replace the radiator today it sprung a leak last week. All seemed good was going thru bleeding process and then I did something I haven’t tried on the car yet. The heater. In Texas we don’t need it much so I havent tried it since I bought it. Everything seems leak free and pressuized fine but once I turn the heater to 90 I get a pretty good drip on pass side closer to firewall. Just looking for suggestions

 

[joegr]

I doubt that you are any exception to the rest of us. You need to replace 100% of the plastic cooling system parts, including the degas bottle. Use Motorcraft for the bottle, not the cheaper ripoffs.

Also, if you didn't turn the heater on before, you are not correctly filling and bleeding the system. You must follow the procedure linked below exactly.
2006 Lincoln LS Workshop Manual

 

[Joey c]

Thanks joe I knew you would come thru with some help. Yes degas bottle is next and I will only use motorcraft. I didn’t make it thru the bleeding procedure before I noticed the leak. Swapped the radiator out and refilled with premium gold coolant. Started her up and let it hit normal temp so the tstat would open up and then I turned the heater on. Nothing was leaking till I turned the heat on and when I turn it off the leak slows almost to a stop or completely stops but when I turn back on starts dripping quickly again. Was wondering if there could be a leak after the dccv since if I understand correctly it stops flow thru the heater when it’s turned off? And would you consider the dccv something that needs to be replaced with the rest of the cooling system. I know they fail as far as climate control goes but do they get brittle and break like the other plastic cooling pieces.

 

[joegr]

Yes, DCCVs do eventually leak, but that would be at the front of the car, where the DCCV is.

Please do note the procedure. You have to fill with the heater bleed removed, and you have to warm the engine with the heater on 90, from beginning to end, not wait till later.