Posting to say thanks to the forum memebers that posted their solutions to heater issues. Specifically the core flush. Soaked core with a pint of CLR for 15 minutes, then flushed. Repeated and reconnected hoses, now heat works fine. Have toasty hot heat in about a mile after startup.
Thanks again, love this forum.

 

I've gotta do this to my TJ soon. The heat doesn't work well at all, but its only a 98 so I'm not sure if the flush will solve the issue.

 

BTW wasn't that much crap came out of the core. Suppose not much needed to impair its function. I noticed a hugh diff in the temp between the supply (really hot 190F) and return (90F) hoses. So before replacing core decided to try flushing.

 

My thinking is that your truck is from 1990, the TJ is from 1998. 8 years is a long time, ya know?