R&R heater core?

[aaalbedo]

I have a 2002 4.6iS 165k miles with an apparent heater core leak (strong antifreeze smell in the cabin when warm). But the carpet is dry and the windshield is not even greasy, so it's either a very small heater core leak or it's coming from elsewhere. I've searched the forum so I know what's involved in replacing, but I'm not entirely sure it's necessary. So two questions:



What other source might there be? There are no apparent leaks around the engine but I'll take a closer look today; might it be sucking the smell in through the cabin air filter?



And if I do decide to replace the core, what other things should I do while I'm there? I know the whole dash has to come out, and I already have the core, a new blower fan, FSR, and HVAC air temperature sensor. I tend to be a long term owner and prefer to spend the money to replace what ain't broke while I'm there rather than doing the job of removing the dash again later. I see the hard pipes that pass through the firewall are available; is it recommended to replace those too while I'm there? No signs of issues with those from the engine bay side.

[upallnight]

Perhaps it's the hard lines going to or coming from the heater core are the one that has sprung a leak. Or the o-rings that is used to connect the two parts are bad.

[aaalbedo]

Thanks for the comment. I have the core with new o-rings, but I've only seen one thread where the hard pipes had corroded so I figured I'd get a look at them first rather than just replacing for another $110. They're not particularly easy to find which also suggests that they are pretty durable.

[srmmmm]

Is the odor stronger when you are in recirculating mode on the ventilation? If so, the heater core or its immediate connection points are most likely. If not, you're picking up the odor from under the hood from a point where the airstream can get it to the cabin filter inlet. I would actually inspect the radiator and expansion tank as possible culprits then.


2002 X5 3.0 387,000 miles
2014 428i 74,000 miles


2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles


1970 Firebird Under restoration

[aaalbedo]

Good point, I haven't fooled with recirc vs fresh.


Engine bay appears to be leak free; PO had cooling system, guides, and valley pan all done very recently and no signs of leaks anywhere besides just enough ps fluid to grease the lines.


I took it on a 60 mile run today, stopping in the middle. Odor was barely noticeable on the drive out. It sat for about 20 minutes, and it was quite strong as soon as I started it back up but back to barely there after just a couple of miles; partly due to desensitization, but there was definitely a big spike after it sat. So that seems consistent with a tiny leak that would continue to leak as it sat hot with no air flow, causing a surge on restart.


I would think that the designers would seal engine bay at the rear of the hood to prevent smelly air from reaching the air inlet, but then again it's had 18 years to deteriorate. I'll inspect that too.