So I bought the pump from Scotty and installed it. It works great, makes a fair amount of noise, though, but that is ok.

Problem is..EVERY TIME I PUSH THE BRAKE PEDAL THE DAMN THING KICKS ON!!!

I can put in a vacuum can to help out with cycle time, but was wondering if there is a way to plumb the engine vacuum, through a check valve to the canister and the pump to the other port so they help one another.

The canister I am looking at has two threaded ports for vacuum and one fitting to go to the booster. Has anyone set up something like this and if you did where did yo get the check valve for the line from the motor vacuum.

I have found one valve online but they want $24 for it and I don't even know if my idea will work.
http://www.vaccon.com/PDFs/Check_Valve_Tech_Sheet.pdf

anybody got any experience with this dilemma???

Mike

I get my electric vacuum pumps from mid-80's Volvos in the local boneyard. They have a large check valve included with the system that isolates the manifold from the reservoir. We also use a large reservior to keep the pump from cycling too often. If your manifold vacuum is less than the trigger point of the pump, you will be running entirely off the pump.
You can also use a regular check valve from a BMW standard booster setup or from an early Camaro/Nova.

How have you got the pump mounted?
Is it mounted in rubber?
I found if you put a hose on the outlet port it quiets the pump a little?
I just bought one of these, although mine doesnt have the built in switch.
I read in the service manual for mine that it is a continous run pump, so it is meant to run all the time and not burn up.
I ordered the mounting bracket for mine, so I havent hooked it up yet, but I plan to use it only for brakes and A/C vacume.
I really dont think I will gain anything from hooking it up to the motor, as I have only 7" vac.at idle.
I will be getting a switch that is on @17" and off@22" so the only time the vac. motor will run is when I use the brakes, that should save the vac. motor a little.
I allready have a vac. can on the car, was thinking of getting ridd of it, but to hear you guys talk I may keep it?
please keep us posted as to how you get it quiet and how it works.
T.C.

I really dont think I will gain anything from hooking it up to the motor, as I have only 7" vac.at idle.

Your vacuum will go significantly higher at your cruising speed and even higher on decceleration.

My pump has isolation bushings but still "rumbles" when it is on. That really is not the problem. When I am at a stop light and "creep" ahead the pump is "on" and "off" about every time I hit the brakes.

Oneofakind...

Can you be more specific on the "check valve" yo uare referring to in your post. I read it as there is a "BMW" part used in a Camaro brake system????
Can this part be purchased at the local AutoZone??

thanks

Mike

From GM:

http://www.drclassic.com/images/parts/55/27255.jpg

http://www.drclassic.com/catalog/Camaro/Brake/M00003-B.html


From BMW:

http://www.bavauto.com/assets/product_images/hardpart/34331151532.jpg

Brake Booster Check Valve - For Vacuum Type Booster
Fits BMW : 2002 / 2002tii / 2500 / 2800 / 2800cs / 3.0 CS / 3.0/Bavaria / 3.0si / 320/6 / 320i / 323i / 528e / 528i / 530i / 630csi / 633csi
Part #: 34 33 1 151 532 ( 34331151532 ) $13.95

Volvo also has a nice inline one.

That one from BMW looks exactly like what I want. I have an import car store right up the road and I am going ot see if they have it if not probably have to go to the dealer.

Oh, and thank you for the info...I will let you guys know how this works out. I might even install a little vacuum gauge to monitor the canister. Can't have too many doo-dad's...

I have 3 vacuum gauges in my car, manifold vacuum, reservoir vacuum and crankcase vacuum.

"Your vacuum will go significantly higher at your cruising speed and even higher on decceleration."

Yea it does 15" at cruise, spikes to 25" at decceleration and drops to 4" durring acceleration and thats where ya get that first good brake pump from.
After that you will still have lousy brakes, no vacume for the second pump.
My vacume can really didnt help that much, and thats why I question if the can attached to the pump will keep the pump from coming on as often, I would think you need a constant source of vacume?
A motor with a big cam is'nt a constant/good source or we wouldnt be talking about this.
I can see a can helping A/C doors, or other small accerories.

I would think the pump will turn off at cruise, and will come on at a stop lite, a can isnt going to hold enough to compensate for a 1-2 min. stop.
Unless the brake vacume system doesnt bleed off any vacume during a stop?
Once the system goes under the "on" setting, the pump will run untill it reaches the "off" setting.
That would mean the pump will be turning on-off while you are at a traffic lite, can or no can.
If I am wrong please tell me, just alot of time and money if it doesnt make any difference.
T.C.

The booster shouldn't leak while you have the brakes depressed, so one pump during a stop should suffice. How big is your reservoir?

I have a Comp Cams vacume canaster w/ guage.
I think Sumitt,Comp, Crane are all about the same size, 7" long x5" O.D..
Im not saying my booster leaks during a stop, I just think under normal driving conditions the pump will be on/off all the time.
Lets say I stop at a lite, let off the brakes enough to role a little, then reaply the brakes, dont ya think the pump will come on?
Or is that where the can would come into play?
I was also thinking of not hooking it to the motor, if ya dont hook it to the motor there is no need for the oneway valve.
But.......is that a good idea? I dont know?
T.C.

That is the problem I have right now. The pump comes on each and every time you depress the pedal even a little bit. The can shoudl help in that it should hold enough volume to get 1 or 2 pumps out of it. My thoughts on attaching engine vacuum is that it might shorten the time that it takes the pump to recover. The check valve is required so that when engine vacuum is below the cut in point of the pump, the pump does not try to suck vacuum from the manifold.

I just noticed this posted by onovakind67:
"If your manifold vacuum is less than the trigger point of the pump, you will be running entirely off the pump."
So if you have 4-7" at idle (big cam)dont bother with hooking into to the manifold.
I know at cruise ya will get 15" but at cruise ya wont be using the brakes and the pump will turn itself off.

Also I can say the vacume can I added to my system did "not" get me another good pump.
I was lucky if it added 1/2 pump if any?
I could also let the car set over nite and still have the same vacume reading in the morning, so it was not leaking.
I did rigg the pump to my brake system today w/o the can and it works great, now all I need is a on/off switch and mabe one of those oneway valves? (I waiting to see what happens here)
Oh yea, I cant hear it over the motor, so noise isnt a problem. LOL
T.C.