wherestheslide

One more thing I need to do before I get near a blend door operation is make sure I correctly top off the coolant. Once I cleared the heater core (just once) I simply hooked up the tubes and was on my way. Yesterday I took the rad cap off, started up and waited for the coolant level to go down so I could add more. But it never went down. Instead it barely flowed out the top for a few minutes, so I am down a bit more than before. Seems like 5 minutes or so is plenty of time for the coolant to circulate throughout, but it never went down. Still no real heat. The overflow tank is at the "max" level also so it is not pulling any coolant back in.

bluedragon436

I know I was able to flush my heater core out... and it worked pretty well... but now after a few months it has clogged back up... on a long trip to SC from DE at that... talk about a very long/cold trip... with snow falling while I drove through the mountains... but anyways... going to flush it again... and this time going to get my complete coolant system power flushed as well... to try and make sure I can get rid of as much gunk as possible... to avoid this issue for a while... I hope!!

wherestheslide

That's a long cold trip.

At this point I need to check the heater hoses temperature. If they are still cold after flushing I am not sure what to look at next.

wherestheslide

OK, so I finaly got around to trying to top off the coolant but it is flat out full, even after idling for a good while. I decided to replace the thermostat thinking it was stuck open and not creating any heat for the heater core. I got one of those failsafe thermos which some folks like and others hate, but the heater hoses are hot now, so that is good. But the heat is still almost non-existent, so next is to take a gander at the blend door.

mls8702

Had no heat and mysteriously slow dissappearing coolant for a year or so. Finally had it checked at a radiator shop after another leaking radiator. The head had micro cracks from bad 2000 castings on the #331 heads. I kept the head and the flux lines are numerous. Had head, radiator,pump,therm,hoses replaced and have "expensive" heat. Have had some coolant puking issues in this 100 deg heat after cutting off engine. system operates at 210 deg. which seems 10-12 deg hotter than I think it should be. I just don't know what temp the 2000 sports 4.0's were designed to run.

phxmark

Mine was a clogged heater core. Back-flushed it with the garden hose and all is good now. Had a lot of "gunk" come out of the heater core.

Paul Dickenson

A Big Thanks to everybody here! This site's saved my butt many times (and kept my wife happy; her cherokee). Flushing the heater core back and forth worked; used some CLR, which seemed to help. Not great heat (never was), but good defrost.

chriskarenkj

Thanks for all the info. Will try and flush heater core, and see if that does anything, then check into youtube video's for the diverter valve.