Weak heat issue

[WSWVIG]

02 3.7 Liberty.

new to jeeps so looking for some insight

Noticed a few weeks ago warm air was coming from the vents, planned on changing the thermostat before the winter anyway.

changed thermostat and put in fresh coolant, also removed heater core hoses and flushed heat core from both ports ( nothing dirty came out)

Initially heat worked good and was hot and now its back to being warm

sometimes itll be hot and then randomly will start blowing warm again

Upper radiator hose is nice and hot, lower isnt as hot as the upper and both heater core hoses are hot so im assuming coolant is flowing through the core just fine


Any tips??

 

[uss2defiant]

get it flushed?

 

[WSWVIG]

get it flushed?

get what flushed?

 

[dude1116]

Are you losing coolant? Low coolant will cause no/little heat.

 

[WSWVIG]

No coolant loss

 

[renegade 04]

You need to re-calibrate the blend doors. The procedure is in the service manual. Index of /manuals/Jeep/KJ

 

[WSWVIG]

You need to re-calibrate the blend doors. The procedure is in the service manual. Index of /manuals/Jeep/KJ

looked through the hvac section and couldnt find anything about recalibration

 

[WSWVIG]

Bump, anyone else?

 

[JasonJ]

Sounds like air in the system to me.

 

[WSWVIG]

What's the best way to bleed the system

 

[ltd02]

What's the best way to bleed the system

What kind of coolant was in it when you started this process and what type did you put in? Should be HOAT. Could be water pump too but (like above) I'd try to make sure all the air is out. You can undo the rad cap on the pressure tank and unscrew the port in the metal piece on the engine side of the upper rad hose. If nothing comes out you can add some there. I've never had to do this on my 02. Always just filled the pressure tank and ran it to warm with the cap off. Topped it off and was good to go. I've done it this way many times over the years.

 

[GunnerSchenck]

I thought the rad cap and coolant tank cap had to be tight before touch the bleeder screw on the upper radiator hose?

 

[ltd02]

Well if there is proper level of coolant in the tank and you open (or at least loosen) the bleeder screw and it doesn't come out immediately then you have alot of air or something blocked. The hope is that this is a high point and the air may find it's way there if it can't make it back to the tank. I used to fill the tank with the bleeder screw open until coolant flowed out and then secure the screw and fill to the correct level on the tank.

 

[GunnerSchenck]

Well if there is proper level of coolant in the tank and you open (or at least loosen) the bleeder screw and it doesn't come out immediately then you have alot of air or something blocked. The hope is that this is a high point and the air may find it's way there if it can't make it back to the tank. I used to fill the tank with the bleeder screw open until coolant flowed out and then secure the screw and fill to the correct level on the tank.

Okay that's the way I do it but I always fill it slightly above then do the bleeder screw thinking then any remaining air will get pushed into the bottle so that's good to know I don't have to worry about that.
I thought you meant you loosen the bleeder screw with the cap off the pressure tank, I do it with the cap on the tank so only reason I chimed in and asked.
Appreciate it :happy160:

 

[Leeann]

The bleeder screw under the hood.

 

[ltd02]

Okay that's the way I do it but I always fill it slightly above then do the bleeder screw thinking then any remaining air will get pushed into the bottle so that's good to know I don't have to worry about that.

I think we're on the same page but I personally seldom have had to do any more than just fill the coolant at the pressure tank and it seems to burp itself. I was sort of thinking since the OP had already filled the pressure tank and it wasn't changing then if he loosens the bleeder near the top rad hose, either air or coolant should come out.

I thought you meant you loosen the bleeder screw with the cap off the pressure tank, I do it with the cap on the tank so only reason I chimed in and asked.

Not when the system is full and operating correctly. The tank is the high point and the coolant should immediately escape out the bleeder. I have removed both the bleeder and pressure cap only when initially filling.

BTW what year is your KJ?

 

[WSWVIG]

Not sure what coolant was in there before and I put in regular green coolant in. Previous owner replaced water pump 6k ago

 

[Leeann]

You need to flush that out and put in HOAT. Mopar or Zerex G05.

 

[ltd02]

You need to flush that out and put in HOAT. Mopar or Zerex G05.

X2. It actually could be the water pump again. If there was any HOAT left in it when it was switched to the green stuff it may have coagulated and gummed up the works. Those two different chemistries don't play well together. They form a sludge when mixed.

 

[GunnerSchenck]

I think we're on the same page but I personally seldom have had to do any more than just fill the coolant at the pressure tank and it seems to burp itself. I was sort of thinking since the OP had already filled the pressure tank and it wasn't changing then if he loosens the bleeder near the top rad hose, either air or coolant should come out.



Not when the system is full and operating correctly. The tank is the high point and the coolant should immediately escape out the bleeder. I have removed both the bleeder and pressure cap only when initially filling.

BTW what year is your KJ?

Okay makes perfect sense now.
And my liberty is an 03 3.7