Vacuum thingee on the firewall
#1
Vacuum thingee on the firewall
Hello,
Can anyone tell me whats the purpose of the black circular part that bolts onto the firewall located right next to the voltage regulator. My car is a 72 Cutlass convertible and its on my 72 cutlass hardtop supreme as well. I think it's some sort of vacuum piece.
What does it do?
Can anyone tell me whats the purpose of the black circular part that bolts onto the firewall located right next to the voltage regulator. My car is a 72 Cutlass convertible and its on my 72 cutlass hardtop supreme as well. I think it's some sort of vacuum piece.
What does it do?
#3
Yes, it stores vacuum to run the A/C vacuum doors and water valve. Without it, the dampers in the heater box will go bonkers when vacuum drops while engine is under high loads.
Inside it is just a diaphragm and spring.
Inside it is just a diaphragm and spring.
#4
I don't think it's necessarily just for A/C cars. My non-A/C '67 Delta 88 has one. It's there to provide a vacuum reservoir regardless of engine speed, etc., and it's needed if anything is vacuum-operated in the heating or A/C system. Even with no A/C, the various vent doors are vacuum-operated.
Mine's circled in yellow below.
Mine's circled in yellow below.
Last edited by jaunty75; September 11th, 2011 at 08:02 AM.
#5
My '68 4-4-2 doesn't have any of those vacuum cannisters on the firewall. They served a number of purposes, depending upon what options are on your car. The '68s that had a remote trunk release (vacuum operated at that time) had a cannister in that position on the firewall. If you had other options, such as A/C, power door locks, and cruise control, there could be as many as 3 of those cannisters mounted at other places under the hood. My car has none of those options; thus, no cannister -just the dimples in the firewall where it/they are supposed to go if the options were present.
Randy C.
Randy C.
#6
Not true for Cutlii. The heater-only system is cable operated, no vacuum. I cannot speak for the full size cars. Of course, this vacuum canister is used for any vacuum actuated accessory such as power trunk or door locks. There isn't a lot of vacuum to pop the trunk when the engine's not running, thus the need for the reservoir. I'm pretty sure there is nothing inside the cannister, by the way. The later cars have an external check valve that is in line with the canister, but the older ones may have the valve built in.
#8
#9
#10
Which is why I specified Cutlii in my first post. I guess the completely unambiguous way to phrase it might have been "Full size cars without A/C also used vacuum actuated doors." I know this is really beating a dead horse, but inexperienced people are sometimes easily confused by phraseology that is not completely unambiguous.
#16
Hate to gravedig, but...
My canister has had one of the vac lines cut too short (black w/ white stripe?), do I just buy a coupling and a bit of hose? Or does it need to have a tee for manifold vacuum?
My canister has had one of the vac lines cut too short (black w/ white stripe?), do I just buy a coupling and a bit of hose? Or does it need to have a tee for manifold vacuum?
#17
Wow! I didnt know these things were worth anything? I removed the one from my car when i made it "heater delete" and just tossed it into the trash can!! LOL. I've probably done that with a lot of 'sellable" parts over the years! Ought to know by now that everything has a "price" -eh? LOL
#18
The only diagrams I find in the manual (attached) refer to the 455 engine (I have a 350). And on everybody's lovely photo of their engine compartments that is always right behind the air filter (just out of view).
#20
let me know if you run across definitive info on what i should do with my 350 hoses...
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