2001 Yukon XL Coolant/Heat Problem

[JSLayton]

I have a 2001 Yukon XL that the heat recently quit working correctly on. It appears to be leaking coolant, as the 'low coolant' light comes on frequently, even right after I add more coolant. If the truck is started and left running to warm up, the air coming out of the vents will not heat up, but if you rev the engine or once you start to go, the air will get hot again. The temperature of the air seems to go up and down based on the RPMs. When the car is parked after running for a while there will be coolant on the ground under the car, so I know that I have to find the leak, but was wondering if the way the heat is working could point me to where the leak might be. Thanks in advance for any help you can give.

 

[domin8]

Sounds like a cracked heater core.

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[JSLayton]

Hopefully this doesn't make me sound like an idiot, but where would that be located and how could I verify that it's the problem? Thanks for the quick response.

 

[chauncey0337]

Can you describe where under the truck it's leaking? Check your heater core hoses going into the firewall. It is a common problem for these heater cores to get plugged up. I had a similar problem, my heat would only get lukewarm. I did a coolant flush and fixed it. If your heater core was leaking, the passenger side floor would be wet and you would be able to smell coolant inside the truck.

 

[JSLayton]

Can you describe where under the truck it's leaking? Check your heater core hoses going into the firewall. It is a common problem for these heater cores to get plugged up. I had a similar problem, my heat would only get lukewarm. I did a coolant flush and fixed it. If your heater core was leaking, the passenger side floor would be wet and you would be able to smell coolant inside the truck.

My passenger side floor board is definitely not wet. The leak is kind of spread out. Almost as if it's spraying out instead of dripping. Should I do a coolant flush?? I've had the car for a few years and have never done one. I did one on my wifes old explorer. Seems like you bought a kit and installed a fitting in one of the hoses that would allow you screw a hose pipe into it. Is that correct??

 

[chauncey0337]

Exactly. I bought a Prestone coolant flush kit and some super flush fluid. I drove around with the flush fluid for a few days(not required). But you can also just do a flush by disconnecting the heater core hoses and using a garden hose. If coolant is spraying, I'd check all the cooling system hoses and radiator. Check with engine on, you might be able to see where it's leaking.

 

[BOSS]

First off, do the flush.

Fill her back halfway to the fill line in the overflow tank.
Add HALF a bottle of the Bars aluminum radiator leak bottle and drive.
Then fill her all the way to the fill line with antifreeze.
Turn the heat on.
Drive 15 miles or so.
(Your light may still come on, depending on how severe the crack in your core is.)
Turn off the truck
Check fluid level...it could be slightly lower.
IF the fluid level is very low, then add the rest of the bottle of Bars.
Otherwise, top off with antifreeze and periodically check....repeat above step if necessary.

B

 

[BOSS]

Also, if the leak is as bad as you say, you need to squirt some water on the radiator and clean off the antifreeze....otherwise you may not know if it's still spraying when you do the above.

B

 

[BOSS]

First off, do the flush.

Fill her back halfway to the fill line in the overflow tank.
Add HALF a bottle of the Bars aluminum radiator leak bottle and drive.
Then fill her all the way to the fill line with antifreeze.
Turn the heat on.
Drive 15 miles or so.
(Your light may still come on, depending on how severe the crack in your core is.)
Turn off the truck
Check fluid level...it could be slightly lower.
IF the fluid level is very low, then add the rest of the bottle of Bars.
Otherwise, top off with antifreeze and periodically check....repeat above step if necessary.

B

This is just a temporary fix.....you may need to flush again and add more Bars later....ultimately you need to replace your core.

 

[NJTaho]

Check all of the hoses going to the radiator, upper radiator hose, lower radiator hose, the 2 hoses going to the heater core. The Heater Core is located behind your glove box and very difficult to get to. You have to take apart the dashboard to replace it. Not an easy task if you are not to handy. It could be as simple as an old cracked hose or as difficult as a cracked radiator. More than likely since you don't have Antifreeze or even smell it inside, it's not the heater core. You are going to have to get under the vehicle and look at the hoses. Use a good flashlight and check. If you are pouring Antifreeze and it is coming out right away without even starting the vehicle, then it could be the resevoir itself that is leaking.

Flushing the system is not the best option right now because you don't know where the leak is.
First thing is to find the leak and FIX it. don't get one of those cheap fixes, if it's an old hose, replace it, if it's just a loose hose clamp get a new hose clamp and tighten it up.
Once the leak is fixed then you can go ahead and do a flush. It's not difficult to do a flush. I did one with a buddy in about an hour after I picked up my tahoe.
Below is a link and it shows how my tahoe coolant looked after I flushed it.

http://tahoeforum.com/showthread.php?p=624544#post624544

Locate the drain plug and Drain the radiator.
once it is almost empty, fill up the Coolant resevoir with water from the garden hose and keep the drain plug off and this will get most of coolant out. Wait until it starts coming out clean.
Put your radiator drain plug back on and fill with your choice of coolant flush cleaner and water from the hose. Follow the directions on the bottle, more than likeley it will say to run the vehicle for about 10 - 15 min. Put the heat on MAX so the heater core is getting the flush cleaner running through it as well.
Turn the vehicle off and drain once again.
Disconnect the hoses from the water pump, not the firewall. The plastic fittings on the firewall tend to break very easily. Run the water hose through the heater core hoses to flush that out completely and once again wait until the water runs clear. While you are there you may want to replace your thermostat.
Once everything has been drained and water has been running clear through everything, you are now ready to fill up with Dexcool. This is the orange coolant, NOT green. You have your choice of getting the 50/50 pre-mixed, or mixing yourself. Either way fill it up and turn the vehicle on again and put the heat on MAX again and leave the radiator cap off so the cooling system and burp itself for a little while. This can take a little bit but shouldn't be too long.

Cap the resevoir and you should be good to go!