Home » Public Forums » GMCnet » Re: [GMCnet] air cleaner sensor leaks
Re: [GMCnet] air cleaner sensor leaks [message #324712] |
Sun, 08 October 2017 16:06 |
James Hupy
Messages: 6806 Registered: May 2010
Karma: -62
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If it were me, I would render the thermactor inactive in the wide open
position and eliminate the vacuum line and potential leak. We use these
coaches pretty much in the summer season, so that air cleaner flap is of
little value. Jwiwd.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Oct 8, 2017 2:01 PM, "Jack Christensen" wrote:
I'm tracking down vacuum leaks on my 455.
The flap that allows warm air from the manifold to get to the carb and help
during startup is controlled by a sensor mounted in the air cleaner assy.
I found that the sensor seems to work properly in that when the engine is
cold, vacuum passes to the flap controller and operates it causing warm air
to enter the engine. What I also found was that when the sensor warms up
it does cause the flap to release as it should, but the sensor then leaks
vacuum when it's warm. It's not a whole lot, but more than I would have
expected. I would expect it seal off the vacuum. Is this usual or is the
sensor bad?
--
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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Re: [GMCnet] air cleaner sensor leaks [message #324713 is a reply to message #324712] |
Sun, 08 October 2017 17:30 |
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pjburt
Messages: 436 Registered: February 2016 Location: Fresno, California
Karma: 1
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Jim, he's in Cal. and has a 76. It needs to work (at least look like it) every 2 years for our bi-annual emissions check.
Wish I could have made it to Paso to meet all of y'all.
James Hupy wrote on Sun, 08 October 2017 14:06If it were me, I would render the thermactor inactive in the wide open
position and eliminate the vacuum line and potential leak. We use these
coaches pretty much in the summer season, so that air cleaner flap is of
little value. Jwiwd.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Oct 8, 2017 2:01 PM, "Jack Christensen" wrote:
I'm tracking down vacuum leaks on my 455.
The flap that allows warm air from the manifold to get to the carb and help
during startup is controlled by a sensor mounted in the air cleaner assy.
I found that the sensor seems to work properly in that when the engine is
cold, vacuum passes to the flap controller and operates it causing warm air
to enter the engine. What I also found was that when the sensor warms up
it does cause the flap to release as it should, but the sensor then leaks
vacuum when it's warm. It's not a whole lot, but more than I would have
expected. I would expect it seal off the vacuum. Is this usual or is the
sensor bad?
--
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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Jerry Burt Fresno, CA.
73 Gmc 26' Canyon Lands
Members: FMCA - GMCMI - GMCWS
A truly happy person is one who can enjoy the scenery on a detour.
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Re: [GMCnet] air cleaner sensor leaks [message #324718 is a reply to message #324712] |
Sun, 08 October 2017 17:40 |
James Hupy
Messages: 6806 Registered: May 2010
Karma: -62
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Sorry you live in California. I didn't think about emissions testing there.
If it was so equipped and sold as a California vehicle, then it has to be
in place and functional when emissions testing is performed. DON'T KNOW
ABOUT FIVE MINUTES LATER. 'EH'. I've been hanging out with some Canadians
lately.
Jim Hupy
Salem, Or ( we don't have emissions testing in this airshed, but, do in
Portland and Medford)
On Oct 8, 2017 3:31 PM, "Jerry Burt" wrote:
Jim, he's in Cal. and has a 76. It needs to work (at least look like it)
every 2 years for our bi-annual emissions check.
Wish I could have made it to Paso to meet all of y'all.
James Hupy wrote on Sun, 08 October 2017 14:06
> If it were me, I would render the thermactor inactive in the wide open
> position and eliminate the vacuum line and potential leak. We use these
> coaches pretty much in the summer season, so that air cleaner flap is of
> little value. Jwiwd.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>
> On Oct 8, 2017 2:01 PM, "Jack Christensen" wrote:
>
> I'm tracking down vacuum leaks on my 455.
>
> The flap that allows warm air from the manifold to get to the carb and
help
> during startup is controlled by a sensor mounted in the air cleaner assy.
>
>
> I found that the sensor seems to work properly in that when the engine is
> cold, vacuum passes to the flap controller and operates it causing warm
air
> to enter the engine. What I also found was that when the sensor warms up
> it does cause the flap to release as it should, but the sensor then leaks
> vacuum when it's warm. It's not a whole lot, but more than I would have
> expected. I would expect it seal off the vacuum. Is this usual or is
the
> sensor bad?
> --
> Jack Christensen - K6ROW,
> '76 Glenbrook/Clasco - "The Silver Bullet",
> Sebastopol, CA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
Patti & Jerry Burt
73 Gmc 26' Canyon Lands -
77 Palm Beach
Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers
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Re: [GMCnet] air cleaner sensor leaks [message #324721 is a reply to message #324712] |
Sun, 08 October 2017 18:18 |
captjack
Messages: 271 Registered: February 2010 Location: Sebastopol, California
Karma: 1
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Senior Member |
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Thanks all,
I like Jim's suggestion. I've never had anyone during the smog check do more than look to see if the hose to the manifold was present. No test of the device. I'm devious enough to make it look like everything is OK.
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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Re: [GMCnet] air cleaner sensor leaks [message #324723 is a reply to message #324722] |
Sun, 08 October 2017 19:08 |
Ken Henderson
Messages: 8726 Registered: March 2004 Location: Americus, GA
Karma: 9
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Senior Member |
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You mean a fix about the size of a BB? :-)
Ken H.
On Sun, Oct 8, 2017 at 7:45 PM, Jerry Burt wrote:
> The stove defaults to no vacuum - closed. A simple fix.
>
>
> captjack wrote on Sun, 08 October 2017 16:18
>> Thanks all,
>> I like Jim's suggestion. I've never had anyone during the smog check do
> more than look to see if the hose to the manifold was present. No test
>> of the device. I'm devious enough to make it look like everything is OK.
>
>
> --
> Patti & Jerry Burt
> 73 Gmc 26' Canyon Lands -
> 77 Palm Beach
> Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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Re: [GMCnet] air cleaner sensor leaks [message #324725 is a reply to message #324712] |
Sun, 08 October 2017 19:55 |
JohnL455
Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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Senior Member |
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Wrong. No vacuum signal is open by return spring (cold air)
Vacuum moves the door against spring tension to closed (hot air from manifold stove)
John Lebetski
Woodstock, IL
77 Eleganza II
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Re: [GMCnet] air cleaner sensor leaks [message #324795 is a reply to message #324712] |
Tue, 10 October 2017 11:50 |
drdonaldg
Messages: 35 Registered: June 2013 Location: San Rafael, CA
Karma: 1
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Member |
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Jack, for the CA smog test the vacuum motor and temp sensor is just a visual inspection. My vacuum motor leaked so I blocked the vacuum source so that there was always cold air to the intake. On our trip to Alaska there were some cold mornings where it would take awhile to warm up so I decided to repair the system. I replaced the vacuum motor and the temp sensor so it works as designed. When the temp sensor is warm and the vacuum motor is in cold air intake position the temp sensor does leak a small amount of air into the vacuum source. There is a restriction in temp sensor to limit the air flow and because the sensor is in an area of lower pressure the amount of vacuum loss is insignificant.
1977 Palm Beach
TZE167V100274
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