Fluctuaning Heater on 200 GMC yukon

[sirhcdeer]

Alright, kind of a weird thing on my 2000 GMC Yukon. I notice that after starting, and allowing the truck to "warm up," the heater does not blow warm/hot air. It's simply cold. BUT, after I begin driving for a length of time, AND at higher RPM's, the heater starts to work--providing warm/hot air.

Now, if I stop and idle for awhile, OR drive at slower speeds with no engine effort (like flat terrain), the heater begins to cool and ultimately blow cold air. But as soon as I drive faster and increase RPM's, the heater warms up again.

What is the deal?!?!

Any thoughts on the matter is apppreciated!

Thanks,

Chris

 

[Rivieraracing]

What's the coolant level at? Are you sure it's full? When was the last time you've changed the coolant and when you did change it did you flush everything out real good? What's the temperature gauge saying when you are idling and when you are driving, does the temp change any at all between the 2 activities?

Alot of things can cause your problem! Low coolant, clogged heater core, sticking thermostat, coolant hose collapsing, bad waterpump or one going out.

 

[sirhcdeer]

Thanks, I'll continue to troubleshoot and evaluate the things you mentioned.

CR

 

[Rivieraracing]

Yeah, def check out the coolant level when it's cold and also check the temp gauge while driving, when at an idle and while driving!!

 

[sirhcdeer]

Well, the coolant was slightly low, and I topped it off with 50/50. I started it up and let the engine come up to temp. It's been very cold in the Seattle area (20's-low 30's for low temps), so I let it warm up for about 5 minutes.

The heater did seem to warm up faster, but I feel it still isn't quite up to par. What I did notice was a gurgling/swishing type sound from what is likely the heater core area (right dash area). I turned the heater completely off and revved-up the motor slightly, which increased the gurgling/bubbling sound. After awhile, it seemed to go away.

I don't know. Hopefully the heater core isn't going out, becauser swapping that out is a freaking nightmare. What exactly goes "out" in the core? It's just a small radiator, right?

Thanks for any advice.

 

[Rivieraracing]

Some heater cores rot out some just plug up!! I'd check the coolant level again the next time the truck is cold to confirm that you indeed have it full!! These trucks can sometimes be difficult to tell if they are indeed full because of the design of the resevoir and that they get dirty and are hard to see! Might wanna think about doing a whole system flush or at least figure out a way to only flush out the heater core real good, sounds like it might just be plugging up and not getting full circulation through it.
What did you trucks temp gauge say while driving and idling?

---------- Post added at 07:33 AM ---------- Previous post was at 07:32 AM ----------

And yes, I bet Seattle has been cold!! It's been freakin cold here in Portland as well, can't wait for summer!! lol