Vacuum pump

C

chuck botts

New member
Oct 2, 1997
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Bought Leigh Harrison new Vacuum pump kit [$265]. Changed its mounting to
rubber shock mounted studs - it is very noisy as is. If the coach has not
been run for some time, the vacuum pump comes on with the ignition switch.
If the coach has been run and there is vacuum left in the brake system, a
push on the brake will dump the vacuum and when you lift your foot the
vacuum pump starts.

I had one experience with loss of vacuum booster and did not want to repeat
it. I didn't think my wife would be able to slow the coach down without the
vacuum booster let alone stop it.

To test the difference, go slowly on the level and kill the engine and pump
the brake to dump the vacuum. Then try to pull the coach down without the
vacuum booster. Then imagine a long down hill grade in traffic with a dead
engine where you had to apply the brakes a lot of times to keep from
running into someone. If you can continually break it without the vacuum
booster, then you don't need a safety backup.

 
Wow $265 for a vacuum pump. I was going to suggest the one that Joe
Mondello sells for $165 but was embarrassed to do so because of the price.
Looks good now.

>Bought Leigh Harrison new Vacuum pump kit [$265]. Changed its mounting to
>rubber shock mounted studs - it is very noisy as is. If the coach has not
>been run for some time, the vacuum pump comes on with the ignition switch.
>If the coach has been run and there is vacuum left in the brake system, a
>push on the brake will dump the vacuum and when you lift your foot the
>vacuum pump starts.
>
>I had one experience with loss of vacuum booster and did not want to repeat
>it. I didn't think my wife would be able to slow the coach down without the
>vacuum booster let alone stop it.
>
>To test the difference, go slowly on the level and kill the engine and pump
>the brake to dump the vacuum. Then try to pull the coach down without the
>vacuum booster. Then imagine a long down hill grade in traffic with a dead
>engine where you had to apply the brakes a lot of times to keep from
>running into someone. If you can continually break it without the vacuum
>booster, then you don't need a safety backup.
>
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
"The beautiful Mohawk Vally"
 
Emery,
You touched on something that has sort of been bothering me. Whenever
I have my A/C on and I am climbing a hill, something inside the unit
(a door I suspect) either closes or opens and changes the flow of air
from the A/C. After cresting a hill the flow of air returns. I have to
admit I never notice it stopping. Now it appears that it could be related
to lack of vacuum as you describe. Another good reason for
a vacuum pump. Am I correct in this assumption?
Richard Waters

>
> ............................................................................ I
> used to have a
> problem with the cold air duct opening when I was going up steep grades (low
> vacuum) but now the pump keeps the vacuum to the heater/ A/C servos.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
 
> Whenever I have my A/C on and I am climbing a hill, {snip}
> After cresting a hill the flow of air returns. {snip}

> Another good reason for a vacuum pump. Am I correct in this
> assumption? {snip}

Uh -- I'm thinking that properly installed, the vacuum pump supplies only
the power brake booster. Am I missing something?

I could see that if you had a bad booster you might have a vacuum leak that
would affect the A/C damper doors, but there must be something I'm missing
here.

Mark
 
Emery --

You are correct sir!
I wasn't paying attention in class!

I was daydreaming about something else. It won't happen again.

Mark

_/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/

>
> Uh -- I'm thinking that properly installed,
> the vacuum pump supplies only the power brake
> booster. Am I missing something?

_/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/

> Mark - you must not have read the posting I made at 11:47 today.
>

Emery wrote in part:

> Also, the pump I got at the
> junkyard for
> $10 included another "T" in the line that was the perfect size
> for drawing a
> vacuum on the 1/8" vacuum line going to the little black plastic vacuum
> tank. I eliminated the small line from the manifold. I used to have a
> problem with the cold air duct opening when I was going up steep
> grades (low
> vacuum) but now the pump keeps the vacuum to the heater/ A/C servos.

And that would solve this problem.
You could also use a one way valve to prevent vacuum loss from the storage
tank.

Mark, going back to sleep...

ZzZzZzZzZzZzZzZzZzZzZzZzZzZz
 
Another option to the secondary vacuum pump is a large vacuum tank. I find
greater peace of mind with a totally passive, non-mechanical supplementary
system

We can kill the engine and then get at least 10 brake applications before
running out of vacuum. I can't envision a circumstance where we couldn't
find a place to "light" with that many pumps available.

We have a 5 gallon tank mounted almost vertically on the driver's side of
the engine compartment. It's tee'd into the line from the manifold to the
booster with check valves to make sure vacuum only flows one way. We were
going to mount it horizontally behind the front cross member, but the tank
we had available is just fat enough that I thought it might reduce air flow
to the radiator. A better choice would probably have been a 3' length of 5"
pvc with end caps and fittings. That would tuck/ in to the space behind the
cross member very nicely.

Just another option.

___________
Dave (& Dege), '76 Royale /_][__] [_] | "SR JAMES"
Santa Barbara, CA *-0------OO--* (our hobby)
 
Hi Dave,
I'm going to be replacing the vacuum line to the
intake manifold. Are You saying I could just
make a tank out of PVC put it inline on the
vacuum line with a check valve...and that would
help. Where would I get the check valve? I
have a autozone right up the road. Do you have
a part number?
Thanks,
Rob Teed 74 Painted Desert
( Leaving for the Keys in 6 days! )

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailto:owner-gmcmotorhome]On Behalf Of Dave Lowry
> Sent: Friday, May 07, 1999 9:09 PM
> To: gmcmotorhome
> Subject: GMC: Vacuum Pump
>
>
> Another option to the secondary vacuum pump is a large vacuum tank. I find
> greater peace of mind with a totally passive, non-mechanical supplementary
> system
>
> We can kill the engine and then get at least 10 brake applications before
> running out of vacuum. I can't envision a circumstance where we couldn't
> find a place to "light" with that many pumps available.
>
> We have a 5 gallon tank mounted almost vertically on the driver's side of
> the engine compartment. It's tee'd into the line from the manifold to the
> booster with check valves to make sure vacuum only flows one way. We were
> going to mount it horizontally behind the front cross member, but the tank
> we had available is just fat enough that I thought it might
> reduce air flow
> to the radiator. A better choice would probably have been a 3'
> length of 5"
> pvc with end caps and fittings. That would tuck/ in to the space
> behind the
> cross member very nicely.
>
> Just another option.
>
> ___________
> Dave (& Dege), '76 Royale /_][__] [_] | "SR JAMES"
> Santa Barbara, CA *-0------OO--* (our hobby)
>
>
>
 
Thanks Dave,
I'm going to make a " Vacuum Tube " out of
PVC and try it out. I don't have time to go
to the salvage yard to look for a booster
before my trip. Thanks for the idea.
Rob Teed 74 Painted Desert

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailto:owner-gmcmotorhome]On Behalf Of Dave Lowry
> Sent: Saturday, May 08, 1999 10:10 PM
> To: gmcmotorhome
> Subject: GMC: Vacuum pump
>
>
> Date: Sat, 8 May 1999 11:27:46 -0400
> From: "Rob Teed"
> Subject: RE: GMC: Vacuum Pump
>
> Hi Dave,
> I'm going to be replacing the vacuum line to the
> intake manifold. Are You saying I could just
> make a tank out of PVC put it inline on the
> vacuum line with a check valve...and that would
> help. Where would I get the check valve? I
> have a autozone right up the road. Do you have
> a part number?
> Thanks,
> Rob Teed 74 Painted Desert
> ( Leaving for the Keys in 6 days! )
>
> Rob:
>
> No I don't. The one in my coach came with the tank, but I understand
> they're really common. Keep in mind that I didn't do the actual install. I
> merely watched, advised and wrote the check. (Same story with just about
> every thing done to our coach.)
>
> IIRC, the valve is at the tank where the vacuum line comes from
> he manifold
> (source), and prevents loss of your vacuum supply if there is a failure
> from the supply side.
>
> In lieu of a steel tank, fittings could easily be added to the end caps of
> a length of PVC pipe (get the higher pressure kind to be safe). The pvc
> "tank" could then be held to the crossmember with either metal band clamps
> or heavy duty tie-wraps.
>
> Others more knowledgeable will hopefully jump in if I've misstated the
> vacuum routing.
>
> HTH
>
>
>
 
Date: Sat, 8 May 1999 11:27:46 -0400
From: "Rob Teed"
Subject: RE: GMC: Vacuum Pump

Hi Dave,
I'm going to be replacing the vacuum line to the
intake manifold. Are You saying I could just
make a tank out of PVC put it inline on the
vacuum line with a check valve...and that would
help. Where would I get the check valve? I
have a autozone right up the road. Do you have
a part number?
Thanks,
Rob Teed 74 Painted Desert
( Leaving for the Keys in 6 days! )

Rob:

No I don't. The one in my coach came with the tank, but I understand
they're really common. Keep in mind that I didn't do the actual install. I
merely watched, advised and wrote the check. (Same story with just about
every thing done to our coach.)

IIRC, the valve is at the tank where the vacuum line comes from he manifold
(source), and prevents loss of your vacuum supply if there is a failure
from the supply side.

In lieu of a steel tank, fittings could easily be added to the end caps of
a length of PVC pipe (get the higher pressure kind to be safe). The pvc
"tank" could then be held to the crossmember with either metal band clamps
or heavy duty tie-wraps.

Others more knowledgeable will hopefully jump in if I've misstated the
vacuum routing.

HTH
 
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