CK5
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79 K5 - What is this part?
- Thread starter BARSTOW_JACK
- Start date
Ported Vacuum Switch
Was used to change the source of vacuum to the vacuum advance to the distributor,or deny vacuum ,according to the coolant temperature,they were also used to control when the EGR valve got vacuum ,you do not want it to open until the engine is up to operating temperature..
Those may still be available but I doubt any parts store will have one on the shelf unless they ordered one for someone 30 years ago and they never picked it up..
Rock Auto may be a good place to look online..be ready for sticker shock possibly,those 70's emission devices aren't cheap or plentiful today..
That switch has a brass or metal base so even if the plastic body broke off,coolant wont just gush out...I'd guess 99% of the vehicles that used those switches had pipe plugs put in place of them when they broke or failed ,and the vacuum hoses re-routed like older ones that didn't have any..
Was used to change the source of vacuum to the vacuum advance to the distributor,or deny vacuum ,according to the coolant temperature,they were also used to control when the EGR valve got vacuum ,you do not want it to open until the engine is up to operating temperature..
Those may still be available but I doubt any parts store will have one on the shelf unless they ordered one for someone 30 years ago and they never picked it up..
Rock Auto may be a good place to look online..be ready for sticker shock possibly,those 70's emission devices aren't cheap or plentiful today..
That switch has a brass or metal base so even if the plastic body broke off,coolant wont just gush out...I'd guess 99% of the vehicles that used those switches had pipe plugs put in place of them when they broke or failed ,and the vacuum hoses re-routed like older ones that didn't have any..
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Actually it is a thermal vacuum switch.
Uses a wax pellet to open and close the vacuum passage, with temp swings.
They come with 2, 3 or more ports.
Guessing here, but yours probably controls the distributor vacuum advance. Also was used to delay egr till eng was fully warm.
Uses a wax pellet to open and close the vacuum passage, with temp swings.
They come with 2, 3 or more ports.
Guessing here, but yours probably controls the distributor vacuum advance. Also was used to delay egr till eng was fully warm.
79 in Cali yeah you need to replace.
Does your truck have the vacuum diagram sticker still?
You will need to find which component this tvs controls that component will be part of the name
Napa would be my 1st go to. Them maybe LMC
Does your truck have the vacuum diagram sticker still?
You will need to find which component this tvs controls that component will be part of the name
Napa would be my 1st go to. Them maybe LMC
diesel4me - Thank-you. Several online sources offered the part which, on my vehicle, is a 4-port. I ordered it from Rock Auto for just under $30.
Wes - I found the vacuum diagram sticker, slightly worn, but legible and photographed it. I circled in red what I think is the PVS/TVS and noted in red on the diagram where the hoses are supposed to run. Any further insights into how this operates would be appreciated.
Wes - I found the vacuum diagram sticker, slightly worn, but legible and photographed it. I circled in red what I think is the PVS/TVS and noted in red on the diagram where the hoses are supposed to run. Any further insights into how this operates would be appreciated.
1 hose goes to the efe valve on the passenger side exhaust manifold, you want this to work. You should see a spring loaded counter weight. Up when cold down when hot. These valves rust and don't move to well.
If rust open not big deal, unless smog tech checks it.
Squirt the shaft liberally with a good rust penetrent, liquid wrench kroil oil, or if you can find it the 1st formula of Mopar exhaust valve penetrent.
I hope the vacuum delay valve is there and is in one piece, if rock auto has that you may want order that too.
The ported vacuum source at carb goes through delay valve to tvs. Manifold vacuum from carb to tvs. Last port on delay valve to distributor advance.
The TV's and delay valves will be marked by each port. Sometimes it a letter that might correspond to component. Other times they are numbers that really don't help much.
Originally the vacuum lines had a rubber block that would just plug on the ports of the TVS, but 40 year old vehicles usually have had the vacuum hoses replaced. My advice if block is missing, take detailed pics and hope the hoses are correct.
If you get me the 8th digit of your vin. I will see if my old smog books at work have operation description, this help figuring out when vacuum is required where.
If rust open not big deal, unless smog tech checks it.
Squirt the shaft liberally with a good rust penetrent, liquid wrench kroil oil, or if you can find it the 1st formula of Mopar exhaust valve penetrent.
I hope the vacuum delay valve is there and is in one piece, if rock auto has that you may want order that too.
The ported vacuum source at carb goes through delay valve to tvs. Manifold vacuum from carb to tvs. Last port on delay valve to distributor advance.
The TV's and delay valves will be marked by each port. Sometimes it a letter that might correspond to component. Other times they are numbers that really don't help much.
Originally the vacuum lines had a rubber block that would just plug on the ports of the TVS, but 40 year old vehicles usually have had the vacuum hoses replaced. My advice if block is missing, take detailed pics and hope the hoses are correct.
If you get me the 8th digit of your vin. I will see if my old smog books at work have operation description, this help figuring out when vacuum is required where.
Wes - Thank-you for this additional explanation. I'll take another underhood look in the morning. I do know the 4-port rubber block is still there as I saw it when I removed the broken top of the TVS. I'll look for that 8th digit of the vin.
The 8th digit is "1"
Actually you are both wrong. It is a Thermal Ported Vacuum Switch.
the switch doesn't care or know the vacuum source.
Ok I have been in the Sierras, I return to work tomorrow
I look and see if we have a vacuum map for your application
