No heat from heater..

[TorK]

Gentlemen, I have a problem with the heater in my '88 Monte SS. To get heat inside the car I have to disconnect the vacuum hose from the valve on the heater hose. If I connect it I have noe heat, butt a hissing sound from the dashboard. Probably a leak, any suggestions on where to start looking??

Tor

 

[pagrunt]

You will have to check the gray vacuum line on the heater control for leaks. Follow it to the firewall then to the water valve by the heater core. Then check the violet/purple supply line from the engine vacuum source back to the heater control. So you know what vacuum line is what, red is heater, yellow is A/C, dark blue is defroster, orange is out side air (OSA), white connects the temp lever valve.

 

[Texas82GP]

Find the hiss and you've found your problem. I've read that the vacuum valve on the back of the HVAC control is available. Otherwise it would likely be just a broken or loose vacuum line.