My 4 wheel drive went out last week still working on that and NOW i have NO fricken heat!

1996 gmc jimmy

The thermostat has been changed, whole system blown out by air and heat still is bad. Cold air is blowing out, but pressure of air is slow. There is not too much different between med and hi. Got any other suggestions? I really don't want to replace heater core.....

 

I would check your vacuum hose (black and about the diameter of a pencil) from the engine to the vacuum resevoire and from the resevoire to the firewall. My sons 95 had that problem. His 95 had a vacuum resevoire mounted under the drivers side of the hood, back by the hinge. Looks like a big black ball. The vacuum line on his was very soft and was leaking badly. If you don't have good vacuum to the firewall, your heater controls will not function properly. The vacuum hose is very easy to replace and should not cost more than a few dollars.

Your heater core would not need to be replaced unless it is leaking or plugged up. If it is leaking, you will smell antifreeze in the vehicle and if it is leaking very much, it will fog up the windows and look like smoke coming out of the vents. As long as your heater hoses that flow out of the core (at the cowl) are BOTH hot, and you don't smell antifreeze in the car, the core should be OK.

 

One line is hot and one cold. Guessing i got a blockage ? ? ? ? Any other suggestions without removing the heater core?

 

Remove the heater hoses from the engine or the heater core. Take a garden hose and use the water pressure to try to flush out any crud that is in the core. Blast one side then the other. Also check where the heater hoses attach to the engine, that the fitting is not plugged. You should be able to stick you little finger in there. Hopefully you will be able to get the crud out of the core.

There has been a lot of discussion about antifreeze on the forum. Some people have had good luck with GM coolant, others not. If there is any question as to what coolant is in the system, drain it and replace the coolant.

Hate to say it, but once the heater core is cleaned out, if you later start to smell antifreeze, get ready to replace it......

 

I had this problem with my 91 and found out that where the heater hose connects to the engine block was corroded so bad that it was blocking the coolant from going into the heater core. I ended up pulling the aluminum piece from the intake it broke so i had to use a pipe ezout to remove the remainder and i replaced it with a straight nipple use a regular piece of heater hose and Bingo instant heat