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My heater is just blowing cold air!!

McJesse

McJesse

NAXJA Forum User
Location
Battle Ground/WA
Ok this is for an 88 cherokee laredo.
I replaced the release valve (which was totally rusted out) the heater still doesnt work just is blowing cold air.
I tried just pushing in the valve manuely and it's not doing anything.

please help me! i want to get this heater working before i go up in the snow this weekend haha
 
do the lines to the heater core get warm?
You say release valve, you mean the heater control valve?

Is the blend door working, you should hear it "flop" over when you move the temp control from hot to col and back again.

Did you "burp" ythe closed cooling system after you had the heater hoses off?
 
Is the engine warming up to the correct operating temperature? Is there a thermostat installed? Is it a 195 degree thermostat?
 
Cab heat is simply a byproduct of engine heat.

Gotta know as Joe mentions if the coolant is at the right temp. Target is 200-210.

Did this happen all at once or gradually?

Yes, if engine is running at 200-210, heater control valve replaced, blend door operation verified, you could have a clogged heater core which is NOT uncommon. Sometimes backflushing with garden hose pressure can (but does not always) restore flushing.
 
87manche said:
do the lines to the heater core get warm?
You say release valve, you mean the heater control valve?

Is the blend door working, you should hear it "flop" over when you move the temp control from hot to col and back again.

Did you "burp" ythe closed cooling system after you had the heater hoses off?
Click to expand...
yes.
no the blend door doesnt work i dont think
no i didnt. to burp it what would you do? just like run it with the hose disconnected? cuz i dont have a fill cap on the radiator i just fill it in the over flow tank
 
birchlakeXJ said:
Cab heat is simply a byproduct of engine heat.

Gotta know as Joe mentions if the coolant is at the right temp. Target is 200-210.

Did this happen all at once or gradually?

Yes, if engine is running at 200-210, heater control valve replaced, blend door operation verified, you could have a clogged heater core which is NOT uncommon. Sometimes backflushing with gardedn hose pressure can (but does not always) restore flushing.
Click to expand...

yeah it works at the running temp. and i would just take the hose to the heater core and flush it out and it probubly doesnt matter which way i put it in does it?
 
You could try switching the heater hoses at the firewall, let the engine circulate the coolant through the heater core backwards.

The hose from the thermostat housing to the coolant control valve (for the heathens its a heater control valve) and on into the heater core is the "IN", the other hose that runs from the heater core back to the WP is the "OUT".
 
McJesse said:
ok so you're just saying swap the hoses so it'll just cycle backwards?
Click to expand...

Yep, same thing as back flushing with the garden hose, just a little less messy, and you don't have to worry about too much pressure blowing the heater core out.
 
Yep, same thing as back flushing with the garden hose, just a little less messy,
========================================================
You garden hose can develop 60 PSI with a good flow at that PSI. Your engine type back flush will not even come close. It's much more likly the high PSI of the garden hose will push cloges out of the core.

Witch way should you hook up the hose?
Try both. I run the water one way untill it runs clear. Then switch.

But a good engine flush won't hurt a thing to.
 
Ok so i back flushed the heater core. the color of the coolant was like rustyish like a surface rust. so i just took the hose to it and flowed it threw the upper and lower hose untill i saw that the water was clear. but it still doesn't work.....

any other ideas?
 
Ok, system isn't real complicated.

Engine heat transfers to coolant, coolant control valve when opened allows coolant to be pumped through the heater core, heat exchange takes place in the air box, coolant continues out of the heater core and back to the WP.

Your heater core could have scale built up enough in its tubes that heat exchange can't take place at an effective level; your coolant control valve isn't allowing enough flow through the heater core; the engine temperature isn't hot enough.

You say the temp gauge is hitting the 200-210 range, and that the coolant control valve is opening. That leaves scaling in the heater core.

Option one: purchase RADIATOR CLEANER, Prestone and Zerex are two brands. This is the stuff you put in the cooling system and drive for 3-6 hours. That might remove enough scale to get you some heat exchange. If that doesn't work go to Option Two.

Option two: replace the heater core.
 
I figured it out! yay it was the blend door. like the wire normally pulls the door open it was broken but i moved it manuelly and there was heat.

thanks agian for everything guys a apreciate it
 
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