[ac427]

Hi Guys,

I have just bought my first Pontiac, a 75 Lemans Coupe. It just jumped out at me one day browsing classifieds and had to go and get it.

Low mile, rust free, old lady southern Sunday church car. Has some mechanical issues, but I've almost got them sorted. It's an emissions car, but they are all removed. Edelbrock intake & 4 BRL and 2.5" flowmaster system.

I need some help with all of the Vac lines and where they go to. I could pull the dash apart and work it out, but being out in the cold doing that does not sound appealing right now.

There are 3 hoses coming through the bulkhead. 1 of them is black and goes into a "T" as soon as it enters the engine bay. the long side runs to a "round thing?" mounted by the heater fan blower motor, and the other side from the "T" is just hanging there. another one runs to a different connection on the "round thing", and the last one just hangs in the open close to the bulkhead. Where are these supposed to go?

I have 2 vac lines to my carb. One to the transmission valve, and the other to the vac advance can - both using the full manifold vac point.

I have messed with it a little. Found that there is a valve on the heater matrix water hose that closes with Vac applied to it - shutting off the hot water and heat. Connecting the 2 open ends on the other lines to a vac source creates a hissing inside behind the dash - hose split or something i imagine.

The A/C system has been completely removed - I'm assuming it will play a part in connecting it all. I can't seem to find information on this. I have been on Autozone's website and looked at their technical diagrams for the vac system but it wasn't much help, really need help from someone who really knows, or can look at theirs and tell me where they go?

I can upload pictures tomorrow if i need to, I know my descriptions may be somewhat lacking!

Thanks

John

[castongu]

Sounds like those lines coming out of the firewall are for your AC system. I only have a '73 service manual to go by, but if the '75 models use the same color codes, Black Plastic line goes to Manifold Vacuum at the rear of the carb, the Grey Plastic line goes to the Hot Water Valve on the heater hose, and the Violet line goes to the Vacuum Reserve Tank ("round thing"). If your hearing a hissing sound under the dash you might have a hose disconnected on one of the Vacuum Actuators for the air blend doors on the heater box, or a spit hose. Could also be the connection at the rear of the Heater Control panel. There's a Rotary Dial on the rear that moves with the position of the lever. Post a few pic's when you have a chance.

[ac427]

Thanks, that nailed it. The hissing behind the dash was from applying vac to the grey line. I'm assuming the a/c system applies vacuum to this when it is turned on and prevents hot water from circulating inside. I guess if the a/c is not turned on using the dash slider then this connection may be open and that's why i was hearing it as it is designed to work in the opposite direction. Now it's all connected as you describe, all is good.

Thank you

[Kbars CanAm]

Anyone got the diagram of the vacuum lines with A/C? I need it for the Can Am even if it is for 73-75 years. Thanks, Kbars

[Alvin]

Originally Posted by Kbars CanAm

Anyone got the diagram of the vacuum lines with A/C? I need it for the Can Am even if it is for 73-75 years. Thanks, Kbars

Here you go, try this for Vacuum Diagrams page link

http://www.autozone.com/autozone/rep...00c152800b13f2

See Fig. 9: for 1977 Pontiac 350, 400