Plain_white_t_tops

The little white vacuum hose on my 79 l-48 that goes through the firewall is brittle and has a hole in it. Can someone tell me what it is for? What is involved replacing it? Thanks in advance.

corvgreg

I'm pretty sure this line is for vacuum to the HVAC control

Street Rat

I think that it is the vacuum supply to the interior ac controls. It hooks to engine vacuum in the engine compartment. It is very common for this hose to break at the firewall.

Plain_white_t_tops

Thank you for the information. Can anyone chime in on what is involved changing this hose? I took the glove box insert out and didn't see where it was.

Z06LMB

I would just follow the tubing back to its source near the intake manifold, carb or perhaps there maybe a a small junction splitter before those parts and just temporarily remove the currently accessible end of this hose. Snip off a small piece of this hose for identifying what you have (if you don’t have any printed information source like a assembly manual). Parts stores like NAPA usually have all the hoses in stock @ about 0.32/ft.

Pre packaged you get about 2 ft. If you don’t know the present length I would get 3 to 4 ft to be safe.

Z06LMB

You will need to identify this vac line under the dash, Checking with an AIM will be your best bet.

SwampeastMike

Judging by the direction that line is headed it may well go to the hot water shut-off valve. The valve is on the passenger side of the engine compartment about half way back. It has two good-sized heater hoses and one tiny vacuum hose attached. If such is the line it's easy to replace as it runs directly between the valve and the switch that you see on top of the HVAC "box" when you remove the glove compartment liner.

Plain_white_t_tops

Thank you Mike, I will be pulling the glovebox liner out and have a look...also a thank you to all that responded.

sparky77

On my 77 with ac that vac line went from the heater hose valve pass side of engine compartment to the vacuum switch mounted to the top of the heater box on the passenger side,when you slide the heater control over to cold it closes the valve to prevent hot water from flowing thru the heater core. I had to replace mine and I also replaced the switch on top of the heater box.