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Discussion Starter #1
I was looking at my service manual to check for the proper order to
bleed my breaks and I noticed the manual specifies 27.56 inHg or more
with the engine running at 1,000 rpm.

My Thomas vacuum pump has a max vacuum of 22.9 inHg.

Is this a problem?

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Discussion Starter #2
For bleeding brakes, a separated tool is use to do maintenance on brake
lines. You can get or see one at a auto parts store. The brake booster
should start working any vacuum of 12 in.hg. or more. Best if the vacuum is
held at or above 15 in.hg.

If the 27.56 in.hg. refers to the brake booster, than it may be a print
error, it may be 17.56 in.hg. for the brake booster.

Roland


----- Original Message -----
From: "John" <[email protected]>
To: "Electric List Vehicle Discussion" <[email protected]>
Sent: Tuesday, September 04, 2007 8:17 PM
Subject: [EVDL] brake booster vacuum levels


> I was looking at my service manual to check for the proper order to
> bleed my breaks and I noticed the manual specifies 27.56 inHg or more
> with the engine running at 1,000 rpm.
>
> My Thomas vacuum pump has a max vacuum of 22.9 inHg.
>
> Is this a problem?
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 

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Discussion Starter #3
Thanks Roland,

I was just using the brake bleeding as a reason why I was looking at
the service manual. I was previously under the assumption that the
Thomas would give the the right vacuum levels.

In the breaks section of the Factory Service Manual,

Under the Vacuum Piping section there is a bit about the vacuum
warning switch:
(0 ohm) vacuum level of 26.7 kPa(200mmHg, 7.87) or less
Infinity ohm vacuum level 33.3kPa (250 mmHg, 9.84 inHg) or more.


Then under Vacuum Pump is says, and I quote:
1. Install vacuum gage.
2. Run engine at 1,000 RPM
3 Check vacuum. Specified vacuum: 93.3 kPa (700 mmHg, 27.56 in Hg) or
more.

In the picture the gauge is connected between the check valve and the
engine.

Assuming its not a misprint:
1)Is have a different vacuum level that what is specified in the
manual a safety issue or does it just make it harder to push the
pedal when I need to stop (I suppose it could be both)?
2) Is there some other vacuum pump available that will get me the
vacuum level specified in the manual?

Thanks.

John



Roland Wiench wrote:

> For bleeding brakes, a separated tool is use to do maintenance on
> brake
> lines. You can get or see one at a auto parts store. The brake
> booster
> should start working any vacuum of 12 in.hg. or more. Best if the
> vacuum is
> held at or above 15 in.hg.
>
> If the 27.56 in.hg. refers to the brake booster, than it may be a
> print
> error, it may be 17.56 in.hg. for the brake booster.
>
> Roland
>
>
> ----- Original Message -----
> From: "John" <[email protected]>
> To: "Electric List Vehicle Discussion" <[email protected]>
> Sent: Tuesday, September 04, 2007 8:17 PM
> Subject: [EVDL] brake booster vacuum levels
>
>
>> I was looking at my service manual to check for the proper order to
>> bleed my breaks and I noticed the manual specifies 27.56 inHg or more
>> with the engine running at 1,000 rpm.
>>
>> My Thomas vacuum pump has a max vacuum of 22.9 inHg.
>>
>> Is this a problem?
>>
>> _______________________________________________
>> For subscription options, see
>> http://lists.sjsu.edu/mailman/listinfo/ev
>>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 

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Registered
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70 Posts
Discussion Starter #5
Hello John,

If that's the vacuum requirement for the brake booster it self, then I would
use the manufacturers vacuum pump and canister design for your braking
system. That's what I did. I use a GMC vacuum pump that is belt driven
that can hold 22 in.hg. for my braking system.

It does not click click either when you are above 18 in.hg. Its only clicks
at the low in.hg. because the check value is closing and opening at the low
rpm startup which you do not hear in a engine vehicle until its reaches
idle.

Roland


----- Original Message -----
From: "John" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Wednesday, September 05, 2007 5:55 AM
Subject: Re: [EVDL] brake booster vacuum levels


> Thanks Roland,
>
> I was just using the brake bleeding as a reason why I was looking at
> the service manual. I was previously under the assumption that the
> Thomas would give the the right vacuum levels.
>
> In the breaks section of the Factory Service Manual,
>
> Under the Vacuum Piping section there is a bit about the vacuum
> warning switch:
> (0 ohm) vacuum level of 26.7 kPa(200mmHg, 7.87) or less
> Infinity ohm vacuum level 33.3kPa (250 mmHg, 9.84 inHg) or more.
>
>
> Then under Vacuum Pump is says, and I quote:
> 1. Install vacuum gage.
> 2. Run engine at 1,000 RPM
> 3 Check vacuum. Specified vacuum: 93.3 kPa (700 mmHg, 27.56 in Hg) or
> more.
>
> In the picture the gauge is connected between the check valve and the
> engine.
>
> Assuming its not a misprint:
> 1)Is have a different vacuum level that what is specified in the
> manual a safety issue or does it just make it harder to push the
> pedal when I need to stop (I suppose it could be both)?
> 2) Is there some other vacuum pump available that will get me the
> vacuum level specified in the manual?
>
> Thanks.
>
> John
>
>
>
>
Roland Wiench wrote:
>
> > For bleeding brakes, a separated tool is use to do maintenance on
> > brake
> > lines. You can get or see one at a auto parts store. The brake
> > booster
> > should start working any vacuum of 12 in.hg. or more. Best if the
> > vacuum is
> > held at or above 15 in.hg.
> >
> > If the 27.56 in.hg. refers to the brake booster, than it may be a
> > print
> > error, it may be 17.56 in.hg. for the brake booster.
> >
> > Roland
> >
> >
> > ----- Original Message -----
> > From: "John" <[email protected]>
> > To: "Electric List Vehicle Discussion" <[email protected]>
> > Sent: Tuesday, September 04, 2007 8:17 PM
> > Subject: [EVDL] brake booster vacuum levels
> >
> >
> >> I was looking at my service manual to check for the proper order to
> >> bleed my breaks and I noticed the manual specifies 27.56 inHg or more
> >> with the engine running at 1,000 rpm.
> >>
> >> My Thomas vacuum pump has a max vacuum of 22.9 inHg.
> >>
> >> Is this a problem?
> >>
> >> _______________________________________________
> >> For subscription options, see
> >> http://lists.sjsu.edu/mailman/listinfo/ev
> >>
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 
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