# Vacuum Pump with No Reservoir?



## Ace_bridger (Nov 22, 2011)

I have found a Volvo 12V UP28 vacuum pump and the seller states that it can be connected directly to the brake servo without the need for a reservoir.

I am sceptical about this and would welcome any commenst or suggestions as to whether this is true or complete poppycock, as we say in the UK 

Ace


----------



## EVfun (Mar 14, 2010)

It is likely true, because the brake booster functions as a reservoir. It has vacuum on both sides of the diaphragm until the brake pedal is pressed, which vents the back side. So without a reservoir you should get 1 brake actuation with full vacuum assist without the pump turning on. If the pump failed to turn on after releasing the brakes you should have at least one more brake actuation with partial assist.


----------



## Ace_bridger (Nov 22, 2011)

If it's true then that's a real bonus. No reservoir, no switch, no associatted work and reduced reliability...I'm sold!!!


----------



## O'Zeeke (Mar 9, 2008)

I've been thinking about this for some time when I Had 2 reservoirs in the Mustang. Removed 1 and made no differences, still 2 pumps till pump went on). Removed the other so no reservoir at all, no difference, still 2 pumps and the pump ran the same amount of time in all 3 scenerios to achieve -15 inches. I will have to study up on volumetrics to get some evidence but in my case it made no difference. I plan on no reservoir in my Boxster 0.0


----------



## O'Zeeke (Mar 9, 2008)

Ace_bridger said:


> If it's true then that's a real bonus. No reservoir, no switch, no associatted work and reduced reliability...I'm sold!!!


Ace you still need a pressure switch or your pump will run continuous


----------



## Ace_bridger (Nov 22, 2011)

Thanks for the input OZ. The seller states that the pump should be wired through a relay which is activated by the brake switch.

I think this has got to be a 'suck it and see' thing...try it and see if it works.

I think it's got to be worth a try, hasn't it?


----------



## O'Zeeke (Mar 9, 2008)

sounds like that may work as long as the pump drawdown is quick


----------



## Ace_bridger (Nov 22, 2011)

What the seller says, an amazingly technical and educated answer...

"95% of all the people who bought this pump, switch it just on the brake switch and claim it is much better then the original (land Rover 2.25 diesel). A few people who want to make it more perfect mount an extra (adjustable) vacuumswitch in the system. So when you switch on contact, the pump starts to let's say, 0,3 bar vacuum. Then with the brake switch take it to 0,6-0,7 bar vacuum. 
This is also mentioned in the mounting instructions.
But you also have to think about a non-return valve which is normally mounted in the inlet of the brake servo. So vacuum stays in for a longer time, if the brake servo is in a normal healty condition."


----------



## jackbauer (Jan 12, 2008)

Just had a look at it. I would say its a rebadged vw/audi pump like what i use. Very effective. Only takes about 3 secs to reach 15in Hg. i use it with a vac switch.


----------



## Ace_bridger (Nov 22, 2011)

jackbauer said:


> Just had a look at it. I would say its a rebadged vw/audi pump like what i use. Very effective. Only takes about 3 secs to reach 15in Hg. i use it with a vac switch.


Hey Jack. So you don't use a reservoir then?


----------



## jackbauer (Jan 12, 2008)

No reservoir but do have a non return valve. its important to put the non return valve between the pump and the vac switch so that the switch senses vacuum in the servo and not the pump else it will just cycle on and off continuously.


----------



## piotrsko (Dec 9, 2007)

It is also important to have a non-leaking booster, otherwise the pump never turns off.

Pump noise does tend to alert little old ladies crossing streets.


----------



## [email protected] (Jun 14, 2011)

I do not have a reservoir with my vacuum brake system and the brakes work fine. The pump comes on every other time I break. 
I let the pressure switch turn the pump on and off.
The switch is fused and wired to the existing fuel pump relay. (don't need that anymore, do we?) Turn the key on; and, on comes the pump until the demand is met. It took a little adjustment to set the switch without gages. (not a big deal) Be sure your connections are tight with no leaks and use a good quality check valve. Car Quest has them for $20.00. Its application is for back brakes on an eighteen wheeler.

Conversion: 1987 Nissan 24 (6v) lead acid. Range 40 miles with 20% remaining battery. 
Heavy conversion and brakes work fine.

Good Luck


----------



## Woodsmith (Jun 5, 2008)

If you need a reserviour I still have the one I made for my aborted MR2 conversion.








It is made from an aluminium fire extinguisher and seems to be quite happy holding vacuum powered from the AC compressor.

I also have the vacuum pressure switch that jackbauer kindly sent to me that I will not be needing for my trike project.

I had installed an off the shelf vacuum guage in the dash to monitor the amount of vacuum in the system as I felt it was prudent to know if the pump wasn't working. Whether it is necessary or not I don't know but it filled the hole in the dash where the fuel guage was.


----------



## PTCruisin (Nov 19, 2009)

I don't use a reservoir either. The pump is plumbed to a check valve first, with the output of the check valve plumbed to a 3-port T-connector with one port plumbed to the brake booster and the other port plumbed to a vacuum switch set to 20 inches of Hg. The vacuum switch actuates a 12V automotive relay that switches on the pump. I also plumbed in a cheap vacuum gauge to an existing vacuum port on the booster so I could set the switch. The pump kicks on for about 4 seconds with each press of the pedal. The braking is actually better than the original system.

I was able to reuse the original vacuum tubing and check valve so the total cost was around $160, with $100 of that being the vacuum pump. Here is a pic of the pump and the 12V relay used to switch it.


----------



## Ace_bridger (Nov 22, 2011)

Thanks for all info and the pics, much appreciated. I will try and replecate what you guys have done.

Woodsmith? Is your pressure switch for sale? 

Just need to do two hours tutoring and I'll have the cash to buy the vacuum pump


----------



## Woodsmith (Jun 5, 2008)

Ace_bridger said:


> Woodsmith? Is your pressure switch for sale?


You can have it for the same as jackbauer wanted for it.

PM me your details and I'll stick it in the post for you.


----------

