Heater core? something else?

Over the last couple years I have had a strange smell in the jeep after driving on the highway for a while. It hasn't been driven much in the last couple years so it hasn't been a huge concern. Now I drive my kids in the vehicle and drive it much more often. It is fairly potent after a while and creates a bit of a headache...it is becoming more alarming now.

I have been "told" that it might be the heater core, but It doesn't have the symtoms. No antifreeze smell (just a strange weird burning smell), no fogging on the windshield, and no leaking on the floor board. However, the heat does have that "just turned on for the first time of the season" smell. Not the same potent smell as I am trying to find out...but you can definately tell the heat is on. I have noticed that ever since I have owned the vehicle though (12 years). I smell the scent more after coming to a stop after highway driving...this also tells me that its probably not heater core.

The smell almost reminds me of burning plastic but I cannot determine where it is coming from. The coolant does need to be changed, but I don't know if that is the issue. The tranny fluid does not smell burnt. I have a leaky rear main but the smell is not that of oil burning. No signs of overheating or head gasket issues...but I don't know for sure. Oil is clear and coolant is clear. I am at a loss and I do realize that this is a "needle in a haystack" question. Just trying to get some ideas.

Any takers?

Check your floorpan and carpeting over the CAT.

I will check it. the system is fully welded and when I installed my warn sliders, under the carpet/floorpan looked good...but I will give it a look again to make sure.

You bring up another possibility. I do have the infamous crack in the exhaust manifold...very small crack however. Not even enough to get me to swap it out yet...still quiet. Could this produce enough really noxious fumes that could get into the cab and cause this issue? I doesn't smell like exhaust though, and I have stuck my nose around the nose around the perimeter of the hood after coming to a stop and don't smell the odor. just weird.

joe_peters said:

Check your floorpan and carpeting over the CAT.

Click to expand...

I now remember a post I read long ago that mentioned putting a heat shield over the cat to avoid heat transfer onto the floorboard. It sits about 1" under the floor (aftermarket carsound hi-flow cat) and I assume there is no heat shield, I will pull the carpet and see if I have some melted carpet under there! Damn, I really hope that's all it is. It makes total sense. I would have never looked for that though. Thanks for the suggestion.

Yeah, some use those "air bake" cookie sheets for heat shields.

Subscribing............. I didn't realize that the Cat gets that hot. Any pics showing how heat shields are mounted?

BINGO! I pulled the carpet from in front of the rear seat and pulled my passenger front seat out. Nothing out of the ordinary. I figured this is where the most heat would be due to the cat. No rust, fire retardant insulation still intact and nothing burnt.

I then decided to check the carpet area under the rear seat in the little storage area...pain in the ass to pull up...why?..Rubber backing of the carpet was completely melted to the floor board...took a whiff...thats it. That is the smell that has been bothering me for years.

Cut the burnt carpet and any padding out of it and replaced with a ceramic thermal fiber blanket that my company produces. I should never had the problem again.

I still would like to eliminate the heat onto floorboard however. Who has pictures/writeup of a homemade "air bake" air shield mounted to the exhaust. I would rather not drill more holes in this floorboard than I have already!

Glad you found it!

Google "airbake cookie sheet for floor pan heat shield", plenty of articles.

Good luck.