Spare gallon can o' vacuum?

[BioFarmer93]

Does anybody know why we have the 1 gallon black spray painted tomato can o' vacuum sitting on the drivers side wheel well? I needed some room to mount some goodies and started looking for places and realized that the vacuum line ran into and out of this can- I remember seeing this can on some of my dad's old ford cars growing up- any way I pulled it off and juist joined the two lines together and everything seems to work the same as always.
So the the question is, why would we need a gallon reservoir of vacuum?

 

[icanfixall]

It hold spare vacuum just like a pressure tank holds spare air pressure...

 

[BioFarmer93]

Yes sir, I was able to figure that much out for myself.. and thank you for the response, but the real thrust of the post was 'WHY". No rudeness intended.

 

[maddenji]

You might want to think of what happens when the engine stops. No pump, no vacuum.
A can of vacuum might be welcome at 60 MPH.

 

[timothyr1014]

keep in mind you have the brake booster, heater controls, and cruise control all ran from vaccum...i know on mine if i rest my foot of the brake with the cruise set I can activate the dump valve without disengauging the cruise....just experimenting i did this one for about 2 miles and then hit the brakes....the booster still worked, just not as well.

bottom line, i am about 95% sure it is just to provided reserve pressure if you have a small leak, or need to use the brake booster without the engine running.....bet right now you wont have the extra 1 or 2 pedel presses after the engine stops

the other side is you just came up with a great way to justify hydroboost.

 

[BioFarmer93]

! Good point! -If my engine stops while I'm doing 60 though, I'm probably gonna have bigger problems than mushy brakes, aye?

 

[BioFarmer93]

Yes, hydroboost... I have been reading a lot here, and wondering why folks need it. My brakes are great! Low input toe pressure produces crazy stopping power. Almost too easy to lock 'em up.. Or is it a feature that is primarily for towing?

 

[icanfixall]

The everyday vacuum assist brakes on our trucks will create around 100 to 1100 lbs of hydraulic pressure in the brake system... The hydroboost pressure is around 2100 to 2200 lbs.... So in the simplest message we that run the hydroboost systems have twice the brakeing available. My brake peddle has always been low because the rear brakes just don't "self adjust" like designed. Now with the hydroboost I never have a low peddle and the brakeing starts right at the top of the peddle with very little applied pressure. My thoughts are if we had disc brakes all the way around we could stop a battleship with little pressure but... The rear drums will work for now. Sure would be nice to be able to upgrade to the F450 disc brake calipers...

 

[LCAM-01XA]

The vacuum can will NOT provide any vacuum for brakes application PERIOD! It is there only for the cruise control operation, I'd imagine it makes it operate smoother or something. The HVAC system of these trucks has no vacuum reserve canister, unless you're like me and added one yourself to somewhat alleviate the issues that come with a weak vacuum pump until you find a replacement for the pump. That said, I did move my factory vacuum canister, I needed the space for relays and wiring for my lights - I will take a pic of where I put the can, it works great there.

 

[BioFarmer93]

I just read a post here a couple weeks ago (with pictures!) about someone putting discs on the rear- looked like a BUNCH O' WORK! I just hope it was worth all the effort. I suppose that if you have the facilities and motivation (not to mention knowledgeable friends) and another daily driver at your disposal, it's all good.

 

[SparkandFire]

I'm on the same train of thought as M.L.S.C. in the fact that the Can 'o vacuum is there to support the cruise control, says so in my Ford '86 Light Truck Chassis Service Manual.

 

[timothyr1014]

I may stand corrected (right now I sit corrected)...it all it does is smooth out the cruise I would gladly switch to full electronic servos and free up the space.

I still think we should say it operates the brakes...it gives justification for the wife to let me go to hydroboost....when she hears her life hangs on the reliability of a 20yr old spray painted coffee can I wll get a quick green light =)

 

[SparkandFire]

I still think we should say it operates the brakes...it gives justification for the wife to let me go to hydroboost....when she hears her life hangs on the reliability of a 20yr old spray painted coffee can I wll get a quick green light =)

If I showed my wife the 20yr old coffee can, she wouldn't ride in my truck ever again!

 

[SparkandFire]

I believe the brake booster is it's own vacuum reservoir... I think that 90 degree plastic connector between the vacuum line and the booster is a check valve, if I'm not mistaken... (which I often times am)

 

[LCAM-01XA]

I will take a pic of where I put the can, it works great there.

And here they are - first general location of relocated canister:

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A better view of the bracket I made for it:

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And what lives in its factory location now

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Yeps, them extra-long brake booster studs sure come handy for attaching stuff to them Oh, and BioFarmer, this is actually what the hydroboost looks like installed, this particular one is a Chevy unit but Ford ones are darn near identical - the bracket for the vac can looks like it would clear a factory vacuum booster as well, but you may have to make it a bit longer, I dunno, just get a tape measure and go to town