2000 Yukon..Heat issues

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ARogg619

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Good Morning All,

So I have this 2000 Yukon I bought as my winter ride / work beast. As its getting pretty cold now, ive been using the heat and lately the heat from the dash is just WEAK. it takes forever to get warm if it even decides to. Now, my rear heat is perfect and warms up just as you would expect. Where should I start with diagnosing this because I want to figure this out asap before its really cold? This is frustrating bc I bought it for winter and to give my Camaro a break but I wound up taking the cover off the Camaro this morning and taking it to work after giving up on the defrost trying to clear the windshield for over 15 minutes. The truck gets up to temp just fine and no overheat issues or anything like that.

Appreciate any help,

Adam
 

Scottydoggs

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if the fan is blowing on full ok. id think the heater core has air trapped in it.

take the coolant tank cap off let the engine run and top it off as needed. can take a little while for it to burp and bleed out the air.

then check the heater hose connections at the firewall for a small leak. as well as the other hoses. fix as needed.
 
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ARogg619

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if the fan is blowing on full ok. id think the heater core has air trapped in it.

take the coolant tank cap off let the engine run and top it off as needed. can take a little while for it to burp and bleed out the air.

then check the heater hose connections at the firewall for a small leak. as well as the other hoses. fix as needed.

Yeah, the fan blows fine, just not hot. ill let the truck cool down and check my levels. I know I don't have a leak bc I have a brand new driveway with zero spots on it ( for now lol )
 

Joseph Garcia

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Is it possible that the valve controlling the flow of hot water to the front heater core is not functioning? With dual heat zones, I am assuming (maybe incorrectly) that there are two separate hot water control valves, one for each heater core. Folks with more knowledge than me in this area will chime in.
 

OR VietVet

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Check the flow thru your heater core. Both hoses, when engine is completely warm, should be about the same temp and hard to hold on to with a bare hand. If they differ in heat then the heater core is clogged. If it is clogged then change the thermostat as well, at the same time.
 
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ARogg619

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Check the flow thru your heater core. Both hoses, when engine is completely warm, should be about the same temp and hard to hold on to with a bare hand. If they differ in heat then the heater core is clogged. If it is clogged then change the thermostat as well, at the same time.

If its clogged, what is involved in clearing It out?
 

OR VietVet

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If is clogged make sure you don't listen to someone who says, "flush it out". A flush is for maintenance and not a repair. If it is clogged it is best to replace it. Flushing it may clear it for a little while but IMO it will get clogged again soon. You never make it like new again when you flush a clogged core.
 
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ARogg619

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If is clogged make sure you don't listen to someone who says, "flush it out". A flush is for maintenance and not a repair. If it is clogged it is best to replace it. Flushing it may clear it for a little while but IMO it will get clogged again soon. You never make it like new again when you flush a clogged core.

Is there a write up for swapping it out? or is it pretty self explanatory? I know on my Camaro I have to remove the dash to get to the heater core, im hoping that's not the case on this big girl.
 

OR VietVet

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My 02 is likely the same and if I could not figure it out or wanted it fresh in my head as I took apart, there is always you tube out there. You can be watching the video and stop it when you check it, till you get to the next step. I always look at 2-3 videos in case someone on there is smart enough to "work smart and not hard".
 

Scottydoggs

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Yeah, the fan blows fine, just not hot. ill let the truck cool down and check my levels. I know I don't have a leak bc I have a brand new driveway with zero spots on it ( for now lol )

i had this same issue on a silerado work truck, the plastic connection leaks so slow you dont see the leak, coolant level drops over a long time, some how the res tank stays at a normal level. then one day the truck starts dinging at you and its over heating. before i found it low on coolant and over heating on me you would have to rev the engine to get any heat if not driving it.

checking to see if both heater hoses are hot is a good check as well like mentioned above.
 

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