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Old 03-29-2011, 07:59 PM   #1
Athens GA
 
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1995 28' Excella
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Vacuum hose help on my motorhome.

Not sure what you call this. My 87 345 needs a new one. Think it has to do with the emissions. It is a block of vacuum hoses connected together. This set is coming off where my thermostat is connected. We think we found it after looking through old books for over an hour at the GMC dealer. What we found was a discontinued part. Anyone know anything about this? Thank you so much for any help.
Dan
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Old 03-29-2011, 09:10 PM   #2
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The part those connect to is called a ported vacuum switch. It allows vacuum to go from the intake manifold to different things on your engine based on temperature. Some of the things that may go to is the vacuum advance on the distributor, heat riser on the exhaust manifold, even the flap valve on the air cleaner snorkel. You might get lucky and find a vacuum hose diagram on the air cleaner housing.
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Old 03-29-2011, 09:21 PM   #3
Athens GA
 
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1995 28' Excella
1989 34' Excella
1986 31' Sovereign
1987 34.5' Airstream 345
Athens , Georgia
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The vacuum hoses are fine as far as I have been replacing one by one. I got to that porter vacuum switch and it is all disintegrated and needs to be replaced. What I need to know is where to get another one. Thank you for what it is called. I can start calling other dealers and if need to part stores. I am a big fan of dealer parts. Unless like car quests puts their name on gates belts. Etc... Thank you again. Oh do you think there is an alternative to not using it. Just negating that whole part?
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Old 03-29-2011, 10:18 PM   #4
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A PVS (Ported Vacuum Switch) has many different uses depending on application. If this were a Ford engine there would be a calibration code for the engine and all of the emission parts could be looked up including the vaccuum hose routing. I assume GM has a similar system. Then you will have to find some one that would have a book for a 24 year old GM engine listings.

OR you could follow the vacuum lines to the devise or devises this switch controls. 2 of the lines will likely pick up vacuum signals from different sources. One line goes to a devise that is to be controlled or operated. The 4th line ..... not sure. Once you find what it controls the switch can be searched for using that description. Meaning the devise controls a xxxxxx. So you would be looking for a PVS that controls a xxxxx for a 1987 GMC with a xxx engine size.

>>>>>>Action
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Old 03-29-2011, 10:58 PM   #5
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Pvs

eBay is a great source of some of these hard to get items.

STANDARD MOTOR PRODUCTS PVS4 Ported Vacuum Switch - eBay (item 220754422701 end time Apr-13-11 06:56:06 PDT)



http://cgi.ebay.com/ACDELCO-212-636-...item3365ffa945

If you can't find one up for bid contact some of the sellers for unlisted inventory.
Good Luck
Dave




Quote:
Originally Posted by Myrtle lynn View Post
Not sure what you call this. My 87 345 needs a new one. Think it has to do with the emissions. It is a block of vacuum hoses connected together. This set is coming off where my thermostat is connected. We think we found it after looking through old books for over an hour at the GMC dealer. What we found was a discontinued part. Anyone know anything about this? Thank you so much for any help.
Dan
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Old 03-30-2011, 12:18 AM   #6
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RockAuto.com shows a 1987 CHEVROLET P30 VAN 7.4L 454cid V8 4BBL (W) OHV : Emission : Vacuum Control Valve that may be what your looking for.
Bill
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Old 03-30-2011, 09:59 AM   #7
Athens GA
 
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1995 28' Excella
1989 34' Excella
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1987 34.5' Airstream 345
Athens , Georgia
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THANK YOU!! I will contact a few of these sources.
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Old 03-30-2011, 07:44 PM   #8
Athens GA
 
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1995 28' Excella
1989 34' Excella
1986 31' Sovereign
1987 34.5' Airstream 345
Athens , Georgia
Join Date: Dec 2007
Posts: 578
Images: 4
So what I did is remove the old dry rotted harness. I just ran new hoses from the PVS to the locations on the engine. Started it up and runs great again. Wow! The new hoses made all the difference on the way it runs. Must have had a leak somewhere. One happy camper. Thank you again for all the help.
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