1999 chevy blazer is giving me lukewarm heat at 0 degrees. could it still be the heater core?

I couldn't find a heater hose diagram specific to the 1999 Chevrolet Venture with rear heat and air, but I can give you the general location of the heater hoses and how to identify which ones go to the rear heat. The heater hoses on a 1999 Chevy Venture are located on the passenger side of the engine compartment. There are two heater hoses, one that is hot and one that is cold. The hot heater hose will be connected to the heater core, which is located under the dashboard. The cold heater hose will be connected to the engine. To identify which heater hose goes to the rear heat, you can look for the hose that is connected to the heater core outlet that is labeled "Rear Heat." The other heater hose will be connected to the heater core outlet that is labeled "Heating Core Inlet." Once you have identified the heater hoses that go to the rear heat, you can reconnect them to the heater core. Be sure to use new clamps when you reconnect the hoses. Here are the steps on how to replace the heater hoses on a 1999 Chevy Venture with rear heat and air: Disconnect the negative battery cable. Drain the coolant from the radiator. Remove the heater hoses from the engine and heater core. Install the new heater hoses. Fill the cooling system with coolant. Reconnect the battery cable. Start the engine and check for leaks.

are the small hoses to the firewall heating up? ck the heater control valve

under the hood to the far left corner you must cut the plastic cover open to expose the blower motor. remove the screws that hold the blower in place, pull the blower through the hole.

back flush your heater core. find the hoses under the hood that go to and from your core and reverse the flow with a garden hose of plane water. you will notice if your core was plugged by the color of the water comming out. put the hose thats coming out of the core in a bucket to see this.

when you turn on your heater and the windshield fogs up is a leaking heater core

You may have vapour lock in your heater lines. Start engine, put heat lever on high, disconnect one of the lines on your heater core, the one on the flow out side, & see if you have any air coming out. Once antifreese comes out stick line back on & retighten clamp. Make sure your cooling system is topped off. Also your water pump may not be functionihg to it's maximum. Take rad cap off cold & view flow rate. If inadequate you may have to replace the water pump. Good luck!

Check the valve on the upper heater hose and make sure it moves,if it does then you need to have the heater core flushed.You can do it your self by removeing the heater core hoses from the heater core and runnin water through it with a garden hose but a rad shop can do a better job.If you choose to do it yourself pick up a bottle of rad cleaner first and put it in the rad a few days before you flush it.

Your '99 Blazer does not have a water valve. Just a temp. blend door. In other words, hot water should be flowing through the core at all times. Like the other techs said, make sure you are getting the whole system full of coolant. You might even try disconnecting one hose, and pouring water into the heater core itself. On most of these year models, if you listen, you can hear the rush of water through the core when you lightly rev the eng. I have replaced 3 heater cores just last year on '96-'99 Blazers. They clog easily. YOu can blow or flow water through them, but if they don't flow freely, I mean without any restriction whatsoever, they will not get as hot as you want. The thing is tiny!

Here's an easy test: Run engine until temp gauge reaches normal: around 180-200 degrees. Reach back to the firewall and grab both heater core hoses. Are they both about the same temp. and HOT? THey should be. If one is much warmer than the other. You are clogged enough to suffer in the winter. And from what you said: "Brrrrrr" You are getting poor performance out of your heater.

BE sure to check that the blend door is working. Is it cool when you set temp to cool? Blazers go through way more heater cores than they do blend doors, so I'm betting your core is either empty, or clogged. TaterTodd

ther are two small tubes that open and close the valve to let in the hot air' one is from right under the carb intake and goes to the right (looking at the engine) right behind the fuse box. if there's o hole in that tube the heat will not work. just change mine becase the tube dry-rotted

the age of the vehicle does suggest the heater core could be plugged, when the motor has been run awhile where is the temperature gauge (if it has one). ?
If i remember right it's not that bad a job to replace the heater core in those trucks... but it's been awhile for me. I would suggest some cardboard or something in front of the rad to see if it warms up at all. if so it is likely a thermostat that needs to be replaced.

Robert