Thread: vacuum canister

Tweet

can anybody tell me what exactly the vacuum canister does? i've searched, but can't seem to find it. even i asked a few fairly knowlegeable people i know, no one seems to know. i feel like i'm asking a dumb question, but i'm really curious

Keeps the engine vacuum for the power brakes if you run a fairly radical cam with a car equiped with power brakes.

well if this is that case, why would they put one on a stock vehicle?

Actually, the vacuum canister has a bladder that is connected to the engine vacuum. When you press on the brake pedal, it opens a one way valve that allows air pressure to assist your pedal imput. Air pressure is applying more force than you are imputting to the brake pedal. Power brakes!!!

ahh, i appreciate the info. my brakes work great, but there's a hose off of the canister that is not hooked up, should it be? or would it be ok like that? sorry to keep pestering

Well, with the hose hooked up you would have power assist brakes. Without it hooked up, you have manual brakes.

ahh, i'll have to check that out, appreciate the help, it's been itchin at me.

I just replaced my brakes on a '92 Lincoln that I have rebuilt and I could have sworn that prior to this, all the lights were working. NOW, my brake lights are not working at all.

I checked the fuses and then I checked my brake light switch and there is absolutely no vacumn getting to it. I traced the line back to the vacumn canister and one of the lines going in is suckin' fine, but the others are not.

Any ideas? Is it time to replace my vacumn canister or could it be something else???javascript:smilie('')
confused

I have owned Mustangs all my life ('65 / '66 / '68 / '95 / '00) and since my back surgery I want to drive something that is big enough to protect me and not so low on the ground - but geesh! I would rather go back to the Ponys than deal with all the garbage I have dealt with on this thing!!!

Thanks for any assistance in this matter...javascript:smilie('')
smile

Sounds like a brake line leak to me.

bdewbre, there are two types of brake light switchs. One, that would more than likely be just a switch that contacts your brake pedal, or a pressure switch that is in a brake line. The brake light switch would have nothing to do with vacuum.

Originally posted by pfcjal
well if this is that case, why would they put one on a stock vehicle?

Your stock vehicle does have one, it's the power brake booster. There should be a check valve between the manifold and brake booster. This is there because the booster has some open space which allows it to store some vacuum, that way when your engine dies you have power brakes for 2 or 3 more stops. If you don't have a check valve, put one in, it is a great safety feature. So, if a vehicle with power brakes already has a vacuum canister, brake booster, then why would you add another? Because more volume to store vacuum means more stops before you lose vacuum. These really radical cams only provide vacuum when cruising at high rpm, so if that doesn't happen very often, you will need a large canister in order to provide you with sufficient vacuum to operate the power brakes for more than a few stops.

Well, I misread what you said even though I quoted you, but what I said holds true for stock cammed vehicles too. You only get 2 or 3 stops on the vacuum in a power brake booster, so the canister adds more.

i appreciate it man, i knew there had to be more to it, see i have one line running from my canister that is connected to somethign, haven't followed it, not sure what, and two more hoses that aren't connected to anything, so wasn't sure if they were supposed to be hooked up, or to what if so, thanks for the reply

Originally posted by pfcjal

...had to be more to it, see i have one line running from my canister that is connected to somethign, ...and two more hoses that aren't connected to anything, so wasn't sure if they were supposed to be hooked up, or to what if so

Hey pfcjal, it seems to me that you are referring to the charcoal cannister and not a vacuum can. If you had two lines attached to a vacuum canister plus the brakes, you would have no brakes, as in nada, zippo, zilsch!

My guess is that you are looking at a charcoal cannister and it's purpose is to take the fumes from the gas tank and send them into the carb. This is achieved via venturi vaccum and not manifold vacuum, sort of like a venting pipe off of a valve cover which goes to the air cleaner.

Manifld vacuum runs 11 to 17 inches whereas the air cleaner has no real measurable vacuum.