The blend door opens up to let outside air into the system... It's located in the HVAC unit behind/under the dash...
My heat in the 5.9 doesn't get scorching hot either, but it's hot enough to satisfy my passengers... Flushing the cooling system several times over the summer helped, but, there's only so much flushing the core can do...
I'll be changing the heater and EVAP cores this summer, as a preventative measure...
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I had really poor heat out put from the heat in my 5.9. I flushed the heater core a few times, replaced the t stat with no change. This past weekend I replaced the heater core, a/c evap core, and all the foam on the HVAC box where the ducting connects to it. I now have blazing hot heat!
You can see all the old foam was in pretty bad shape.
I replaced the foam with new stuff I picked up at the hardware store.
1998 Grand Cherokee 5.9 - DT headers, Kolak 3" exhaust, 2" BB, K&N CAI
Wasnt the Blend door. Temps got to 55 today and heat worked fine. So I know my Heater Core is clogged and needs replacing.
Mechanic wants $510 dollars for labor. Which is insano. Going to wait for the summer to do this repair. Thanks for all your guys
help much appreciated.
All I can say is if it's below 30-35F outside my Jeep with 180F thermostat only blows slightly warm to completely cold air and I have to leave it on recirc to get warm-hot air. So keep that in mind but also keep in mind my Jeep runs at 180F not stock 190F. If you get warm air out when on recirculate but not on anything else that, in my opinion, tells me it's just simply too cold outside for the heater core to bring the temperature up to something hot. But it sounds like you've never properly done a cooling system flush and that it's clogged a lot of stuff up. You never even said if you actually flushed the system when you replaced all these parts or just drained it, closed the valve, and filled with new coolant. Please make sure to reply to all questions/comments someone posts on here there are a lot of knowledgeable people on here but they can't do much when you only answer half of there questions and suggestions.
To properly flush you need to drain the cooling system, fill it with store bought distilled water, run it for a minute or two, let it cool down, drain it, refilled it with radiator flush and distilled water, let it idle for at least half an hour to an hour, let it cool off, drain it, then repeatedly fill and drain the cooling system with distilled water till it is perfectly clear and finally fill with a 50/50 mix of coolant and distilled water.
I can not stress enough always wait for an engine to cool before draining its coolant, and never ever I don't care what anyone says ever put home water in a cooling system I don't care if you're only using it to flush it don't do it distilled water is $0.80 a gallon, you can get 20gallons for like $16.
System was flushed by me, but I couldnt get to the heater core, too cold out side. didnt wanna freeze up the water.
Also I didnt have a compressor to blow out the heater core. I will Just wait for the summer and replace the damn thing.
2 years I had the truck and she treated me well. hopefully I get a fwe more out of her.