Hello,

I have a 95 5.2l 1500 with no heat in the cab. Truck gets up to operating temp fairly quickly but only throws cold air in cab. I changed the water pump on it about 10,000 miles ago, but the thing never really has had warm air. Now I cant even defrost my windshield.

I have read something about air being in the heater core. Whats the process of fixing that? Also if that doesnt work what is my next step?

Thank you!

 

Try backflushing the heater core first. Once done, try and keep as much fluid in the core as possible when you put the hoses back together.

 

check the vacume lines that go thru the fire wall on the passenger side of the engine compartment they get brittle and break the heat controls are operated by vacume if these lines break it will not work properly also a sign of the vac lined broken is if you fan only blows to the defrost

 

A 95 should have a cable operated blend door. You might want to see if it broke or came off. Even with no vac you should get heat out the defrost vents.

 

You remove air by burping the cooling system. Put the front on ramps or pointing uphill, turn heat to full hot, remove radiator cap and run truck for fifteen minutes. Probably doesn't matter if heater is turned to full hot, as there is no heater valve on these trucks, but I'd do it anyway.

I'd run some radiator flush through the system, then pull off the heater hoses where they attach to engine block (not at the firewall, too easy to deform the pipes going in). Flush and back flush with hose, make sure pressure is low at spigot.

Before you do all this, run truck to normal temp and feel heater hoses going into firewall...if they are both hot, your heater core is good and you need to start looking elsewhere, such as airflow and duct issues.

 

If you haven't selected "heat" in a long time, the deteriorating foam seal on the blend door may have it stuck shut.

 

Thanks for all the quick responses. I will check all of that out.

So for the dial on the dash that turns cold to hot....how does that work on my 95? There is a cable from what I understand and do I have to take the dash apart to feel behind there and does that cable run down to the heater core?

 

Cable. Yup. And it goes to the TOP of the heater box... so, unless your dash has already fallen apart, the only way to get to it, is pull the dash. The axle for the blend door DOES stick out the bottom of the heater box a little bit though, enough that you can put your finger on it, turn the ****, and see if the axle moves. Should be able to hear the door "thump" shut from one extreme to the other as well.

If ya look under there, the axle protrudes just a bit, just to the passenger side of the trans tunnel.

 

Well I pulled the lines from the heater core and flushed them both ways with a garden hose. Then I filled the lines and heater core with antifreeze and connected the lines trying to keep as much air out as possible (which seemed to be impossible). Then I started the truck and ran it for 20 minutes with the radiator cap off. I had a crazy amount of heat. So much for the first 150 miles I had to turn the thermostat down on a cold day for the first time ever. Now, I have marginal heat once again. More air in the system? How do I get that out?

Thanks

 

On the passenger side of the engine, the heater hose should have a splice right about the middle of the valve cover, disconnect it there, clamp off the engine side, so it doesn't dribble.

Pull the other hose off the steel pipe that goes into the water pump on the drivers side, and plug the steel line. (I used a small cork)

Put both hoses up as high as you can, and fill the longer hose with the liquid of your choice. (those being water, or coolant, nothing else. )

Reconnect the hoses, keeping as much fluid in them as possible. That should make a difference.

Another alternative would be to buy a flush kit, and install one of the hose unions on the outlet side of the heater core, right under the cowl. (nice and close to the heater core.) Start the engine, radiator cap off..... and crack the union open a bit so air can escape. When coolant starts flowing out, screw it back tight. This might actually work better, but, don't know for certain. (something I really need to try.....)