i got a suburban and it has no interior heat. I have replaced thermostat, inline valve, and the heater core is getting antifreeze. Yes it is hot!!! i burnt my hand on it! I checked the air doors, and such for the climate control and all work.. i am lost. I have a gm master tech, and my uncle who is a master lexus/nissan tech... we all cant find anything. any input wouould be awesome

 

blower works? if it blows and thhe core is hot you have heat somewhere. ducting all hooked up? had an old bronco and heat defrost door did not work. no heat but you could cook in the glove box. ducting to defrost off and door would not go to floor
Clark

 

well the thing is everything works in the system. the diagnosis at this very point is that the system will build no pressure. If you rev the crap out of the engine, you get heat inside but after 45 seconds you loose heat again.....

 

What year is the Suburban?
Although there is water in the heater core, is it flowing through? Is there any chance someone disconnected the hoses to do some work and put them back on the wrong connections?
See if you can trace the water path from the pump back to the radiator.
Jim

 

Have you checked to see if all the vacume line are hooked up? If one has a leak or is loose the doors won't work right and won't let the air flow were you want it. Just a thought.

CRIS

 

the suburban is a 99 and the heater hoses are properly hooked(they are two sizes so its hard to mess up) and the vaccum has been good. Although the heater doors and mode doors are all hooked to electronic actuators.

On the idea of the flow i dont know how well it is actually flowing. YYou realy cant see it moving throught the cap, but if you have the cap off and rev the motor the coolant moves down and then up when you lt off the throtle. I am amazed at this issue and so are the other techs... itsa bigger issue though because its my mom's car.

 

If the heater core is getting hot and air is coming out of the vents, I would say it has to be the door that switches between heat and cool.
I dont see how the flow volume thru the heater core could prevent the system from blowing warm air if the core is remaining warm.

 

i checked the doors though, and they work fine. The major deal is though if i rev the engine or if i put a pressure terster on it while running it will have heat! then you take off the pressure tester or let off the throttle 30 seconds later its gone.

 

Then have you tried replacing the cap?

 

yah that is the first thing we did, still nothing fixed, it seems as though there is no pressure.... but it hold pressure when it is hot or cold with the pressure tester...