I have a 2001 Blazer LT 4x4 and I'm having issues with the cooling system. To keep it short I've replaced the radiator , water pump, fan , thermostat, and clutch assembly recently and I've bled the cooling system. Since then my heater randomly blows warm or cold air. The temperature guage shows it's at operating temperature but the water in the radiator is barely warm. Same with the hose going to the heater core. Vents all work normally. Any idea why it won't actually get warm? I've put 3 thermostats in it during the last year.

 

First thought is that you might have air trapped in the heater core.

When filling the cooling system it can help to remove one of the heater hoses to make sure the heater core has coolant in it.

The blend door actuator that controls the heat can break too.

 

Thanks. I'll check to make sure the heater core has fluid. The actuator appears to be working fine. First time I've had this issue since I got the car. I change antifreeze evey year and never had a problem.

 

My thoughts as well on the air trapped in the heater core. It can often be a chore to get all of the air out of the core when refilling the system. The best advice I can give short of using a vac system is to position the truck on a slope with the front end of the truck higher than the back end and the cap side of the radiator at the highest point. As much slope as you can have back to front, the better off you'll be. You don't need a whole lot side to side.

 

Thanks. I tried that for about 20 minutes but got no bubbles. I'll try to find a steeper incline and I'll pull the hose off the heater core and see how much flow of antifreeze I have going through it.

 

Last time I refilled my cooling system, I left the front end on jack stands and filled it with one of the heater hoses removed at the firewall. I might have also back filled the hose I removed. Only after I started seeing water come out of the heater core pipe while refilling did I reconnect the hose.

 

Thanks. I'll try that.

 

Thanks for the help. Backflushed the heater core. Hose out was barely a trickle. Got a lot of junk out of it. Car warms up faster and the heater is working alot better even though the engine hasn't warmed up all the way yet. Bled the system again but got no air bubbles so hopefully it's fixed. No leaks anywhere that I can see.