# Vacuum troubles



## dimitri (May 16, 2008)

Here is the pic of my setup, hopefully you can make it out. I had to use several brass connectors to get all my connections in place. I used plumber's tape on each threaded connection and made it very tight.


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## Greenflight (Sep 13, 2007)

Make sure the range on the switch is wide enough. IIRC I set my pump to shut off at a little over 20 and turn on at about 15-16. If you have it set to too small of a range even a tiny leak will cause it to constantly cycle.

Other than that just check for leaks...


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## Jimdear2 (Oct 12, 2008)

dimitri said:


> I just hooked up my Thomas vac pump to a master cylinder, same way I done it on my first EV build. This time I also have the vacuum meter that came with the pump and I can adjust the screw on the vacuum switch to whatever level its triggered on.
> 
> My question is what is the typical vacuum level I should maintain for proper brakes operation? I checked the car workshop manual and can't find vacuum level numbers. Current level which is default switch position it came with is -20 in Hg. Is that high or low or normal?
> 
> ...


dimitri,

Pump up the system, then isolate the pump and lines fromn the booster and check valve. plug the line and start the pump if it stll cycles fast then find the leak and fix it.

The booster should hold vacuum for at least a couple of minutes. If after a couple on minutes you step on the pedal and there is no assist the problem is check valve (easy fix) or internal booster valve (bring money).

Good luck


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## tj4fa (May 25, 2008)

dimitri said:


> My question is what is the typical vacuum level I should maintain for proper brakes operation? I checked the car workshop manual and can't find vacuum level numbers. Current level which is default switch position it came with is -20 in Hg. Is that high or low or normal?


In Tampa you are at sea level and the pump should pump up to about 25Hg. For each 1000' of elevation above sea level, the vacuum will lose a 1Hg. Elevation compensation is also why it may not show up in shop manuals.

Around 25Hg could be your high and you could set your cut in at 20Hg or a little lower.



dimitri said:


> The biggest issue is that its not holding the vaccum level, it drops within 15-20 seconds to the point of triggering the pump again, which is very annoying. On my first EV built it was holding for several minutes before tripping the switch again, without touching the brake pedal.


Do you have another auxiliary vaccuum tank or just relying on the original brake booster of the car?

One thing to check is the check valve on the brake booster and the grommet that its plugged into. The grommet could be cracked and leaking or the check valve bad. 

You can suck/blow into the check valve and it should restrict in one direction and allow the pressure to flow in the other.

My brake booster diaphram was bad on my Ranger so I replaced it with a new one that included a new check valve and grommet.

An auxiliary brake booster reservoir in combination with the original brake booster will give you more brake vacuum reserve and the pump won't run as often. 

On the other side of that, is that the more reserve you have the longer the pump will take to fully vacuum the system down.


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## petty (Jan 24, 2009)

dimitri said:


> I just hooked up my Thomas vac pump to a master cylinder, same way I done it on my first EV build. This time I also have the vacuum meter that came with the pump and I can adjust the screw on the vacuum switch to whatever level its triggered on.
> 
> My question is what is the typical vacuum level I should maintain for proper brakes operation? I checked the performance auto parts car workshop manual and can't find vacuum level numbers. Current level which is default switch position it came with is -20 in Hg. Is that high or low or normal?
> 
> The biggest issue is that its not holding the vacuum level, it drops within 15-20 seconds to the point of triggering the pump again, which is very annoying. On my first EV built it was holding for several minutes before tripping the switch again, without touching the brake pedal.


In a typical car, the power brakes work off of a vacuum level of about 16 inches of mercury, so a similar level of vacuum must be provided by the pump. Take your car to the nearest mechanic to troubleshoot it.


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## tj4fa (May 25, 2008)

petty said:


> In a typical car, the power brakes work off of a vacuum level of about 16 inches of mercury, so a similar level of vacuum must be provided by the pump. Take your car to the nearest mechanic to troubleshoot it.


Sounds like a leak somewhere that he should be able to track down.

Below is a procedure to check for a vacuum booster leak. There's many more out there on Google that might help as well.

I remember one (I can't find at the moment) where you take another car's vacuum line from it's engine that would go to it's booster (while it's running) and plug it into the suspected vacuum booster on the other car to test it.
http://books.google.com/books?id=mN...rIn4Dw&sa=X&oi=book_result&resnum=1&ct=result


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## dimitri (May 16, 2008)

Thanks everyone for feedback, except the one that advised to take the car to mechanic , are you kidding me? I haven't taken my cars to mechanics in years. 

After reading up on your responses and searching old threads on the subject I decided its easier to start over and redesign my vacuum setup. I think the pump itself is not holding vacuum and I had no check valve anywhere, apparently check valve was integrated inside of OEM vacuum hose that I didn't use. Luckily I found that hose in the pile of old crap that I took out of the car, indeed there is a little bulge in the middle, check valve. I will use this hose between the pump and the rest of the rig now, so hopefully it'll hold better. I also have not planned on vacuum tank, but now I want it, so I made one today, 4" diameter, 15" long, that's as big as I can go in the space allowed.

I still have some work to do, but it's coming along nicely, I'd have to wait for rubber mounts I got off Ebay today, to minimize pump vibration.

Thanks again!


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## tj4fa (May 25, 2008)

dimitri said:


> ...I also have not planned on vacuum tank, but now I want it, so I made one today, 4" diameter, 15" long, that's as big as I can go in the space allowed.
> 
> I still have some work to do, but it's coming along nicely, I'd have to wait for rubber mounts I got off Ebay today, to minimize pump vibration...


I put mine in the back of my truck buried under the tool tray in the rear of my battery box.

It's actually floating on top of a piece of 2" foam to soak up any vibration but it's not going anywhere contained in the battery box.

I can't hear it when it's running unless I open the back window and strain a bit. I plan to run a light on the dash to tell me when it's running just for fun.

_Note: Edited to remove photos with suspected bad check valve location._


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## dimitri (May 16, 2008)

I see a potential problem with your setup. Your switch is on the other side of the check valve from the tank. So its not measuring vacuum in the tank, its measuring vacuum in the hose between the pump and the valve. If vaccum leaks faster on this side, but still good in the tank, the pump will turn on for no reason. I think it would be more efficient to have the valve right after the pump, and have switch and tank on same side. Does it make sense? This is how I hooked up my new rig today and its working great.


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## tj4fa (May 25, 2008)

dimitri said:


> I see a potential problem with your setup. Your switch is on the other side of the check valve from the tank. So its not measuring vacuum in the tank, its measuring vacuum in the hose between the pump and the valve. If vaccum leaks faster on this side, but still good in the tank, the pump will turn on for no reason. I think it would be more efficient to have the valve right after the pump, and have switch and tank on same side. Does it make sense? This is how I hooked up my new rig today and its working great.


Hmmm....I don't see what you're saying here and haven't had any problems at all. 

I'll have to dwell on this a bit...


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## cdtomlinson (Apr 3, 2009)

I hope this is a good thread to post this, because I am just starting a conversion and just found out there is a need for a vacuum pump. Is there a standard pump that I can scrounge or mod to do what is needed? How do you control turn on/turn off points? The picture looks like a well pressure switch and I have one of those. Does the base ICE car have enough vacuum storage, or do I need something extra to store more capacity? Thanks for any guidance.


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## tj4fa (May 25, 2008)

cdtomlinson said:


> I hope this is a good thread to post this, because I am just starting a conversion and just found out there is a need for a vacuum pump.


If you removed the ICE engine which supplies vacuum to a vacuum assist hydraulic brake system and you want to keep vac assist brakes, then you will need a vaccum pump.

You can also use standard hydraulic brakes without vaccum assist as long as you have strong leg muscles.



cdtomlinson said:


> Is there a standard pump that I can scrounge or mod to do what is needed?


There are a couple different store-bought types and you might also be able to slavage a vacuum pump from some vehicles in an auto salvage yard or from RVs. Here is a link to some that can be found in specific year autos that you might be able to salvage from older GM cars: http://www.evdl.org/pages/gmvac.html

My pump is a GAST 12VDC vacuum pump I bought through Electric Vehicles of America (EVA) and some others here talk about a Thomas pump.



cdtomlinson said:


> How do you control turn on/turn off points?


The Square D pressure switch I have turns the pump on and shuts it off when the vac pressure reaches a set value. The Square D switch has both settings and are like 5Hg apart.

One thing about vacuum settings is that at sea level the Hg can be around 25Hg and for every 1000' of elevation, the Hg drops 1lb so the settings are different depening on elevation.

My settings at sea level are 25Hg shut off/20Hg pump on give or take an Hg or two. 



cdtomlinson said:


> The picture looks like a well pressure switch and I have one of those.


Yours may work. This is thebrochure that came with my pressure switch. http://ecatalog.squared.com/pubs/Machine%20Control/Condition%20Sensors/Vacuum%20Switches/65013-101-25D.pdf



cdtomlinson said:


> Does the base ICE car have enough vacuum storage, or do I need something extra to store more capacity? Thanks for any guidance.


Most people who use vac assist brakes seem to add another reservoir to the system. I used 3" diameter X 18" long Sch 40 PVC pipe with caps glued to the ends and then drilled and installed brass barbed air fittings.

I used 5/16" fuel/vacuum line and bought a one way check valve as you can probably see in the photos I posted earlier in this thread. I have a little extra capacity in the lines from the rear of the truck to the Vaccum assist canister on the firewall.

One thing with the original vacuum system is that the check valve and the grommet on the ICE vacuum cannister needs to be good or it may leak out quickly and cause your pump to run more than necessary.

Hope some of this info helps.


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## cdtomlinson (Apr 3, 2009)

Sounds good. I am on a budget (I'm a teacher in my other world), so I will probably look for what I can get at the salvage yard. I have a really good mechanic to assist me, so he can test used pumps to verify they work. I have lots of PVC here on the farm, so no problem building the extra reservoir.


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## tj4fa (May 25, 2008)

The 12VDC GAST pump I have is model MOA-V111-JH and as you can see this pump is rated at 1/16HP and pulls .8CFM of vacuum.

http://www.wainbee.com/suppliers/Gast/diaphragm/pdf/moa.pdfhttp://jaxed.com/cgi-bin/sd.cgi?cat=pts&fil=vacuum+pump&state=&submit=go


You can check this Jaxed.com link for vacuum pumps on Craigslist and it looks like there is one out there from a GM for $30- and others you might check into.

http://jaxed.com/cgi-bin/sd.cgi?cat=pts&fil=vacuum+pump&state=&submit=go

I would imagine other types of vacuum pumps (like Air Conditioning work pumps?) might work provided they are DC or can be inverted to DC.


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## tj4fa (May 25, 2008)

dimitri said:


> I see a potential problem with your setup. Your switch is on the other side of the check valve from the tank. So its not measuring vacuum in the tank, its measuring vacuum in the hose between the pump and the valve. If vaccum leaks faster on this side, but still good in the tank, the pump will turn on for no reason. I think it would be more efficient to have the valve right after the pump, and have switch and tank on same side. Does it make sense? This is how I hooked up my new rig today and its working great.


I think I see your point and today I reconfigured the check valve even though I had no vacuum problems with the brake (but maybe could have if a leak presented itself downstream to the main vaccum reservoir on the firewall (not shown here).

Here is the new configuration and I will drive it around and see if I notice any difference.


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## mvest (Jan 22, 2009)

I have a question? I have a Thomas pump to start with. This did not come with any cut in/cut off switch. Now I'm pretty sure the old ICM had a vaccum/sucking. The Thomas pump has arrows pointing out the flow of air and after I hooked up, I noticed it's actually 'blowing' air out of it. Could someone tell me if this is correct or should it be in a vaccum? Also is there any other cut in/ cut off switch other then the 'big gray box'? Thanks


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