I have 1998 F-150 and the heater core was replaced 18 months ago. All was going well until about 2 weeks ago I noticed under heavy acceleration I would smell antifreeze. The smell would clear up and would not re appear for a day or so. Finally the other day when it was 8 outside I got in the truck and got about 5 miles from the house started up a hill and it was like a fog machine was mounted behind my dash the windows fogged up almost immediately so I figured great the core went bad again. Now the temperature has warmed up the last couple of days and there is nothing no fog in the cab the heater works fine just an occasional slight smell of antifreeze. Before I go through the trouble of tearing out the dash is there anything I should check I already checked the connections on the firewall and they were fine.

 

It certainly sounds like a heater core. Let me be the devil's advocate here. Who replaced the heater core 18 months ago? You or somebody else? If it was somebody else, are you sure they actually did it? In other words, are you sure that somebody didn't throw some stop leak stuff in there and tell you they changed it? It's a huge job, and I just don't trust a lot of people anymore. Do you smell antifreeze coming out of the panel vents on the dash?

 

If was my buddy's truck and the core was out when I bought so part of the agreement was he would have the new core put in. I picked up the truck from the service garage who said it took them 8 hours to do the job. I hope they were honest enough to put a new core in since they charged my buddy for $650 to do the Job.
Yes the smell comes from the panel vents in the dash and when it smokes the smoke comes from there

 

Okay. Considering the possibility of "variables" there, you probably are stuck with taking the dash back off and looking at it, and probably replacing it again. You need to replace the blend door and the coolant while you're doing it (I'd bet good money the repair shop didn't do that). Here's a youtube video of the job. It's very good. For the record, that's not a bad price at all for the job, but sometimes you worry if you get what you paid for.

 

Thank you

I will tear into this tonight

 

Read this before you start.

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