Thread: Plugged heater core?

So after searching I haven't found a definite answer.

Starting yesterday being a cooler day, I noticed my heat was intermittent. I had it set on around 75 and had heat, then it seemed like it was blowing cooler, then it got hot again, so I thought I was imagining things.

This morning it did almost the same thing. Then this afternoon, setting it on 75 felt like I had it set on 65.

My first thought was the coolant was low and bypassing the heater core. I stopped at Advance Auto and picked up some coolant and topped off the overflow, as it was almost empty. The car was still hot so I couldn't check to see if the radiator needed any added.

The whole way home it was the same with almost no heat at 75, but would get hotter air if I jacked it up to 90.

The operating temperature is in the normal range so I am just looking for confirmation, or other possible solutions.

By the way, I should add the coolant system was flushed around 103k miles according to a sticker under the hood. It stands just shy of 127k now so I don't even know if a flush is an answer.

Thanks in advance.

UN hook the hoses at the core and flush it with a garden hose

I was actually thinking of doing that today.

I'll report back with any changes.

Well I think I have eliminated the heater core as a culprit. I flushed it out and everything seemed to flow out well. Took it for a ride and no heat. The ONLY time I get heat, is if I set the climate control to 90. Anything below that is cooler air.

is there a blockage someplace else in the system maybe?

i have a heater core issue too in my 05, but i get heat, just got sloshing lol gotta to a fancy bleeding lol

Blend door might actuator might not be working correctly, or a bad temp selection switch.

Dunno about temp selection switch. AC works as it should. Had it set to 69 today and it kept things about how they always are. I tried turning the passenger controls on and it doesn't make a difference.

I've seen the blend door mentioned before, but no one has described what I'd actually be looking at. I've worked on lots of cars over the years, but never did much with the HVAC, becuase I've never had an issue, other than changing a few heater cores.

When I got home this afternoon I grabbed the heater core hoses and both were equally hot. I wasn't running the heat so that should indicate that coolant is flowing as it should thru the heater core.

That is unless I am thinking about this the wrong way.

Make sure you bleed the system very good in these cars.. The sloshing sounds like air in the heater core.. does it make the noise when turning or stepping on the gas hard?

^^mine does that occasionally