Heater core?

My girlfriends blazer is having trouble heating. It goes in and out of hot and cold temperature. It seems to heat better when we drive on the highway. I checked the engine gage and it is running at a normal temperature making me think it is not the thermastate. There is no anti-freeze in the floor board leading me to believe it is not the heater core. I checked all the hoses I could see visibily and none of them were disconnected. What do you bleieve the problem is?

The problem you describe is kinda strange. Since the problem is isolated to the cooling system that simplifies things a bit. Start with the basics. Inspection of the coolant level and condition, hose for leaks, hoses for mushiness/old, any coolant leaks from the engine, cooling system / radiator cap pressure test, any strange tapping noise from the engine or gurgling noise, and the smell of coolant either under the hood or inside the cab.

Note : You can also have a tech use an IR gun to heat probe the system for restrictions. Also inspection of the heat control valve.

My best guess based on your strange description of the problem. You have a water pump impeller/bearing problem. This could create cooling system flow problems. My next guess is that the thermostat is sticking.

What ever the problem turns out to be. Always remember to have basic cooling system inspections done first. You may find that an old cooling system has more than one problem. Remember to have the cooling system flushed when service is going to take place.

Where is the heater core located the smell is in side

I replaced the heater core in my truck why is the heat still not working?

Anti-freeze was misting out of my air conditioning vents so the heater core in my 2001 Chevrolet Blazer was replaced. The car has 85,000 miles. The anti-freeze smell is still coming out of the vents and is stinking up the car. Does anyone know how to clean the anti-freeze from the vents and from inside the car?

The heater core on our 2001 Chevy Blazer is failing and needs replaced. When replacing the heater core, is it necessary to drain the air conditioner coolant? Purging and recharging the a/c is very expensive if it is not absolutely necessary. Thanks for your advice.

Directions on changing heater core

I have a 2001 Blazer and the heater core started leaking on it last summer. On page 18 of this Blazer forum is a question titled "Accessing the heater core on a 1998 Blazer". That caught my attention since I needed to replace mine. Thanks to the technician I got all the info I needed to do the replacement. I posted some pictures to give you an idea of what you'll be looking at if you do it yourself. It's NOT a project I'd suggest getting into unless you have the time, tools and patients to complete. Something I learned the hard way, three weeks after I replaced the heater core it would only blow out hot air. There's a little gizmo called the blend door actuator that makes the air blow over the A/C evaporator coil or the heater core, or both. Mine died and guess what? You have to pull the dash to get to it too! If/when you have this done have them replace the actuator. They're not expensive and could save you several hundred dollars by not having to pull the dash again just to replace it.

Heater problem
2001 Chevy Blazer 6 cyl Two Wheel Drive Manual

Just replaced the heater core. I have heat and no more leak. Without tuning on anything while driving. Air is coming out of the vents.. Can adjust the temp by just turnig the temp dial? When I do turn on the heat it comes out of all of the vents. Floor and the defrosters. So I have no control on the dials. What is wrong? Just happy for heat.

The door actuater on top of the heater core is that run on electric or vaccuum?