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Hi all, doing work on my 86 Cadillac Fleetwood Brougham and I just replaced my intake gasket and now I’m trying to replace all my vacuum hoses. The only modification I’ve made is that the vacuum hoses for all the AIR equipment has been bypassed since I removed my AIR pump. So far I have most of everything hooked up but there’s a few things that are missing from the diagram under hood. I seemingly have 2 vac tanks and 2 manifold vac ports. One vac tank has 2 fittings for vac lines that’s near the HVAC box and the other next to the charcoal canister that only has one fitting for a single vac line. So going off both the diagrams under hood and a diagram I found off the caddy forums I understand that one of the manifold vacuum ports is supposed to go into a branch off into the cruise control servo and a vac tank then from the vac tank into the anti dieseling solenoid. But that leaves at least one of the manifold ports and vac tanks unused. I also found what I believe is a vacuum check valve amongst the old vacuum tubing. So I was wondering where does the extra manifold port, extra vac tank and the vacuum check valve plug into all this? Or should I just cap the manifold vac port and call it a day?
Minor updates
found a piece of hose running straight from the firewall, no idea if it’s for the heater water valve or the ecc vacuum harness. Anybody have any ideas?
Last edited by Scuffed98; December 19th, 2023 at 09:03 PM.
One of our members; Kuseetha, has a 307 in an 80s Oldsmobile. He provides a link in the following thread with some suggestions on removing CCC carburetor components from 307s.
I suggest you keep all of the vacuum fittings and lines as they were from the factory. This means you'll need an Oldsmobile (Cadillac) service manual for your car to make sure you are using the correct vacuum diagram. Either that, or remove ALL of the smog equipment from your car and install an aftermarket carburetor and distributor. BTW, do cars require smog testing where you live?
No smog testing required where I live.
I did read up on that post from kuseetha but it doesn’t really cover anything relating to the vacuum lines for cruise control and hvac. Tried doing some reading from the service manual and it doesn’t really tell me anything useful other than saying that the hvac and cruise control should be connected to vacuum while providing no diagrams or descriptions on how it should be connected to vacuum. You’d think GM would’ve documented this stuff better than providing a generic diagram under hood lol.
More updates, did some more digging and found a black hose coming out of the firewall under the brake booster. I traced it to ending to a T connection next to the cruise control release switch. Can anyone confirm or deny whether or not this is the vacuum hose for the HVAC programmer?
I thought the HVAC vacuum lines had colored stripes on them?
Probably time to perform some acrobatics, get under the dash and ensure the other end of that vacuum line goes to the HVAC controls. Make sure you stretch first.
Hi all, one last update. Turns out that hose coming out of the firewall is the HVAC hose. Plugged it into the manifold vacuum and my HVAC pretty much works as intended. So right now I have the HVAC and the CC connected to its own manifold vacuum port instead of having the CC connected to the emissions stuff like in the diagram above. I might make an updated vacuum diagram to include the extra vac tank, HVAC and CC.
December 19th, 2023, 05:28 PM
