I got 98' 4.6 Scab with 103k..I guessing it is the heater core, but have not seeing coolant loss yet. When I get on it the Antifreeze smell gets stronger.

 

Sounds like heater core for sure.

 

if you put the defroster on and the windshield gets fogged up on the inside its the core for sure...zap!

 

Yep - The smell is just the early warning system.

Get it swapped out before you start to experience coolant loss (on your carpet).

E...

 

I just bypassed the heater core for now...thanks

 

I had this happen to me on my '97 supercab 4.6....definitely the heater core.
The dealer wanted around $1100.00 to replace the $37.00 core! 99% labor for this repair. I decided to tackle it myself with a Haynes manual at my side. Took 2 full days - you have to remove the entire dash to get at the air box that houses the heater core. A huge PIA......I paid the grand to have it done on my wifes '98 Expy when the hot/cold mix gate failed iin the airbox. I didn't need the back pain again.. I'm 6'3". I hope there are some other threads on this site, because it is a big job to take on. Good luck!

 

I have done 4 now. Takes about 8 hours if you don't want any parts left over. It is too lenghty a procedure to just type it up here. Get a good manual and follow the instructions.

JMC

 

It is a true PIA, but well worth the $1100.00 saved. Basic tools and time is all you need. Buy new quick-disconnect coupling seals also. $$$$$$$$$$$$$$$$$$$$

 

In general when you smell coolant inside, it is a heater core. Change it immediatly as the vapors can and will get you sick if you don't change it.