Vacuum Stuff

[WhiskeyBottle2]

Howdy Everybody,

Well I've been working on my 86 6.9l n/a vacuum system. Some of you know I asked a few questions earlier. The coffee can on drivers side appears to do nothing...it's not even hooked up...The little tuna can on the passenger side that has a vacuum line and 3 wires hooked up to it appears to do nothing. Unhooked the vacuum to it and no lights, alarms, or anything happened...so I don't know what it is or does....and finally there is a black plastic softball sized ball that has a vacuum line to it...I unhooked it and plugged the line and I swear my Max A/C seemed to work much better, but again I don't have a clue what the plastic ball is for...

I used to have cruise control, but it was broke so I just took it off cuz I don't use it anyway...Ok, this is a long post, and I can't find a vacuum diagram anywhere so I was hoping someone could steer me to one or if someone in the know could school me about all this vacuum stuff...

I'm not worried about losing vacuum and needing an alarm or light to tell me as I have a vacuum gauge. But again it would be nice to know what these vacuum things are so I can decide if I can get rid of them or not..

Thanks alot...

 

[smokinpipes]

Hi there:

A quick answer to your question(s)
The coffee can is simply a vacuum reservoir with a check valve for the cruise control servo as this servo can consume a bit of vacuum, it has it's own supply if you will.
The other side of the truck is your round ball. That is for aiding in removing the pulses from the vacuum pump as it is operating and there is a vacuum load on it. It simply helps keep the vacuum at a constant as opposed to the pulsing from operation for the next three things:
The transmission modulator.. if you have bad vacuum you will have very rough shifts,
The Environmental controls (if you have the factory A/C).. when moving the controls and dampers the air valves can use a bit of vacuum and the ball will supply some of it in low speed engine operation... and lastly:
Your tuna can with three wire plug in it. That is a low vacuum warning indicator. If you have a low vacuum situation, it will illuminate your 'BRAKE' light on your dash to warn you there is a problem, no vacuum, no power brakes.

If you have no A/C, no cruise, and a manual transmission, you could pretty much remove the vacuum system all together if you have the hydro boost from an F450.

 

[WhiskeyBottle2]

Vacuum System

Hi there:

A quick answer to your question(s)
The coffee can is simply a vacuum reservoir with a check valve for the cruise control servo as this servo can consume a bit of vacuum, it has it's own supply if you will.
The other side of the truck is your round ball. That is for aiding in removing the pulses from the vacuum pump as it is operating and there is a vacuum load on it. It simply helps keep the vacuum at a constant as opposed to the pulsing from operation for the next three things:
The transmission modulator.. if you have bad vacuum you will have very rough shifts,
The Environmental controls (if you have the factory A/C).. when moving the controls and dampers the air valves can use a bit of vacuum and the ball will supply some of it in low speed engine operation... and lastly:
Your tuna can with three wire plug in it. That is a low vacuum warning indicator. If you have a low vacuum situation, it will illuminate your 'BRAKE' light on your dash to warn you there is a problem, no vacuum, no power brakes.

If you have no A/C, no cruise, and a manual transmission, you could pretty much remove the vacuum system all together if you have the hydro boost from an F450.

Thanks...that's what I needed to know

 

[franklin2]

I would imagine the one on the pass side is standard issue on all the trucks, and is definitely needed on a gas truck, since as you pull a hill, a gas engine loses vacuum. They have a check valve over there to let the HVAC system use the vacuum from the storage unit when the engine doesn't have any vacuum. If you didn't have this, each time you pull a hill, your heat/air would go to the defrost vents at the windhshield, and the when you got to the top and vacuum was restored, it would switch back.

Since a diesel has a separate pump, I would not think it would be needed as much, but if you ended up pumping the brakes and using a lot of vacuum to the booster, I don't know if you would starve the system enough to make the HVAC controls switch to defrost, but I think that would be the least of your worries if you are using the booster that much.

I believe you still need vacuum to the system, even if you only have heat and no A/C.

 

[smokinpipes]

On the trucks with no A/C installed, there is only three settings.. "Off - Heat - Defrost" and it is cable driven. No vacuum needed. That's how my 84 is setup.

 

[WhiskeyBottle2]

Needing Vacuum

I would imagine the one on the pass side is standard issue on all the trucks, and is definitely needed on a gas truck, since as you pull a hill, a gas engine loses vacuum. They have a check valve over there to let the HVAC system use the vacuum from the storage unit when the engine doesn't have any vacuum. If you didn't have this, each time you pull a hill, your heat/air would go to the defrost vents at the windhshield, and the when you got to the top and vacuum was restored, it would switch back.

Since a diesel has a separate pump, I would not think it would be needed as much, but if you ended up pumping the brakes and using a lot of vacuum to the booster, I don't know if you would starve the system enough to make the HVAC controls switch to defrost, but I think that would be the least of your worries if you are using the booster that much.

I believe you still need vacuum to the system, even if you only have heat and no A/C.

I agree that even a diesel needs vacuum. Now that I pretty much know the functions of the various parts to the vacuum system, thanks to the help from everyone...I can figure out how to get the low vacuum part working even tho I have a gauge. My next question is since I don't have cruise control anymore...I wonder if I can use the "coffee can" for another backup reservoir for the power brakes. The can is in good shape and does hold a vacuum, but I am not sure if the internals will allow it to work with brakes...

 

[rhkcommander]

As far as i know the reservoir is just a big hollow cylinder meant to give you a couple stops worth. Dont quote me though, just doesnt make sense why it would be much else. If your real worried about losing vac run dual vac pumps like the ambulances.
Wouldnt be too hard to rig.

 

[Leeland]

I thought the check valve at the grommet on the vacuum booster is meant for "the couple stops worth" by not letting the stored vacuum in the booster to escape back out.

I'm curious what that 'tuna can' is as well. Does the vacuum line on yours run to the vacuum line tree? After pulling my engine I spotted mine on my drivers side fender well below and slightly behind my DS battery and next to it was a appropriate sized vac line running up to the vac line tree. Mine also has no warning lights on.

 

[rhkcommander]

Could be. Wouldnt make sense for what i said if there was a vacuum leak. Just throwing out my WAGs.

Maybe it is there to smooth out transitions between sudden loads such as slamming the brakes - a can has more area for a vacuum than the hose. Perhaps without it the vacuum heater controls could go into defrost. Just guessing

 

[WhiskeyBottle2]

Well guys after taking the coffee can out and hooking it up to the vacuum tree I found that the one hose barb named vac will pull vacuum thru the can and sucks air in thru the other barbed hose hook up. Reverse it and the can wiil hold a vacuum so there must be a check valve inside.

What this means is...if you cap the side not marked the whole can can be used as a reservoir. If you use the other hookup where you hook up to the unmarked side you would only have half a can reservoir and you can leave the side marked vac uncapped.

So...I am going to cap the one side and use the whole can as a reservoir along with the round ball and I should have plenty of reserve vacuum. I don't know why, but it seems like extra insurance if the vacuum pump goes out while going down a mountain.

 

[smokinpipes]

In reply to the couple inquiries about the the tuna can, I will restate, it is meant to turn on the brake light on the dash under a loss of vacuum situation. At the age of these vehicles by now they work intermittently at best.
I am fortunant to have a working unit in my truck, and when my vac pump went out, I would let off my brake peddle and the brake light would come on for several seconds. You can test the tuna can by smply disconnecting the vacuum line going to it and turn your ignition on. Your brake llight should come on aafter several seconds. If it doesn't, consider it inop, and can be tossed.
I plan on installing a vacuum guage to have an in depth view of my vac system.
Just yesterday I lost my vac pump belt and the brake light only came on breifly then extunguished itself. I had the hardest shifts and. Try stopping a 1ton dually with no power brakes. I think I bent my seat brackets a little bit. Lol

 

[Leeland]

Hey whiskeybottle, have you tested out the new canister routing to see if you get a extra assisted brake application?

Smokingpipes, I must have missed it the first time, thank you. That explains the random brake light a while back.

 

[WhiskeyBottle2]

Extra...Extra...Extra...Braking Assist

Hey whiskeybottle, have you tested out the new canister routing to see if you get a extra assisted brake application?

Smokingpipes, I must have missed it the first time, thank you. That explains the random brake light a while back.

Yes I did test it...What I did after hooking the "black ball" and the "coffee can" together I unhooked the vacuum pump vacuum line from the vacuum tree on the firewall and quickly capped the port on the tree that the vacuum line was hooked to. I did this while the truck was still running. I then drove the truck down to the end of the street and back. I used the brakes 4 times and the truck stopped normally. The fifth time the brakes were hard to stop the truck. Now, I was only going about 10 mph, but I am confident I would have enough reserve vacuum to stop easily if I lost the pump. I wouldn't know about towing and going downhill tho...This is why trailer brakes should be in good shape.

Anyway, I hooked the 2 cans together using a "Y"...and I think I would like a check valve somewhere between the vacuum pump and its hookup at the tree just in case the pump went out and the reserve vacuum don't leak back thru the pump...


Well there ya go...it worked for me at 10 mph, but I think it works....

 

[smokinpipes]

Philosophical question, but if your vacuum pump went out, and even with extra reserve on hand, wouldn't you still find out 'all of a sudden' unless you have some sort of indicator / gauge?
For instance, I lost my van pump belt going down the freeway and didn't realize it until I was merging into traffic after getting off. Truck didn't want to shift into third until 40MPH; but that was my clue, that I had one power assisted brake press left. The point is, I didn't know I lost it until, well, I had almost no brakes. lol

 

[WhiskeyBottle2]

Knowing If I Lost Vacuum?

Philosophical question, but if your vacuum pump went out, and even with extra reserve on hand, wouldn't you still find out 'all of a sudden' unless you have some sort of indicator / gauge?
For instance, I lost my van pump belt going down the freeway and didn't realize it until I was merging into traffic after getting off. Truck didn't want to shift into third until 40MPH; but that was my clue, that I had one power assisted brake press left. The point is, I didn't know I lost it until, well, I had almost no brakes. lol

Yeah I hear you! And not to be disrespectful...but I think I did mention somewhere in this thread that I have a vacuum gauge!...You are right to say...what good is the reserve vacuum if you can't know if you lost a vacuum belt or pump...

I would say...you must have a vacuum gauge...period...I really don't know why our trucks didn't come with one considering the nature of the vacuum system...Some may say a vacuum gauge is overkill, but I am a firm believer that "real" gauges are a must to really monitor every aspect of the truck...particularly the engine...

But yes I do have a vacuum gauge and it gets scanned with the eyeballs just as I scan the tach, speed-o-meter, oil temp, coolant temp...& such, as well as my mirrors...Kewl!!!