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Pulling Intake Manifold - What maintenance items should I do?
So, over the Christmas break I am going to pull the intake manifold off to change the PCV lines and to change the oil pressure sensor (along with a relocation kit). I see that it is a good idea to also replace the passenger side air check valve while the manifold is off.
What else should I do while the manifold is off? The wiring harness seems awfully brittle during the little bit of poking around I've been doing - can/should that be done?
I've got the PCV hardlines setup (with PCV valve), the DPE oil pressure sensor relocation kit (pricey but very high quality), manifold gaskets, the air check valve, and, of course, a bunch of new tools - clamp pliers, fuel line removal tool, an inch-pounds torque wrench, hose loosening tools. I do need to check to see if I have a 1-1/16 socket but it's cold in the garage and I don't want to get out of my chair right now (so, later). Anything else I need to have on hand or will wish I had when I am elbows deep in engine grime?
First, use a paint brush and vacuum to remove any sand and dirt around the manifold. When you pull the manifold it drops right into the intake ports of the heads. Once the manifold is off, stick the smallest vacuum tool you have into each port to pull out any particles that might have dropped in there.
Look over the knock sensor. GM did have a bulletin on using RTV to set up a dam around the sensor to prevent water intrusion. Only certain years were affected but might be worth investigating to see if your car is affected by the bulletin.
Look over the vacuum hoses behind the manifold and block. Age cracking may have started and this is a good time to replace if they are brittle.
I would also replace the intake gaskets if you haven't already bought them as you will likely find them well compressed and full of grit.
Not sure how often you plan to pull the manifold, but while its off you can bypass the throttle body coolant line. Doesn't provide any more power, but does make future removals easier.
Last edited by vettenuts; Dec 14, 2017 at 08:05 AM.
I replaced the knock sensor harness while I had my intake off. The wiring seemed OK but the rubber seals were hard and loose in the holes. I think it was around $25.00 for the whole harness. I also put the silicone dams around the rubber seals.
In addition to all the above comments a good thing to replace is the o-ring between the throttle body and intake manifold. Sometimes they become flat with age.
When reinstalling the manifold be sure to reattach the very small black vacuum line into the connection at the rear of the manifold.
Originally Posted by oelarse
Below is the vacuum point on the rear part of the intake.
Big port goes to the brakebooster and the smallere port below the MAP sensor goes to the lower point under the vacuumtank shown on the last photo .
Hope this help
Originally Posted by zachaeous
The vacuum supply tube that goes from the back of the intake to the vacuum tank at the bottom of the passenger fender runs inside a wiring harness behind the intake manifold:
I replaced the knock sensor harness while I had my intake off. The wiring seemed OK but the rubber seals were hard and loose in the holes. I think it was around $25.00 for the whole harness. I also put the silicone dams around the rubber seals.
Yep, bit the bullet on this as well - ordered a new harness and two new sensors - might as well do it when I have it all apart. Thanks for the suggestion.
I did this couple months ago when I went with the Dorman LS6
Intake Manifold.. I can't really tell you if I gained anything since
I did headers, rockers & the intake at the same time.
I doubt that it's worth 20hp ever.. But if it keeps the heat
out of the intake, it's doing something.
2020 Corvette of the Year Finalist (performance mods)
C5 of Year Winner (performance mods) 2019
I highly doubt that shield will give you any hp at all... once the air is in the intake manifold there isn't much more distance for it to travel to get to the combustion chambers and at wot that air is moving so fast that any reduction in heat from that shield may not effectively remove any heat from the intake air charge... then again I could be completely wrong
That's a lot of rwhp noted on the chart - most likely a turbo or s/c application. In that case any reduction in intake charge temperature would be beneficial. Most n/a engines here make a lot less power, so any benefit would be much smaller. Not saying that the heat shield noted has no merit or that it is useless - just trying to put it into perspective.
The next time I have the intake off I will relocate the passenger side auxiliary check valve to the right bank and remove the piping for it behind the manifold so that the valve is easily replaced or serviced in the future. You will need some parts as shown here:
If your car is earlier, it will have the rear "steam ports" (coolant air bleed ports) on the heads connected to the front ports. If not, connecting them to the front ports will make getting the air out of the heads easier on coolant changes and maybe reduce the chances of rear cylinders running hot. Bill Curlee used a front coolant air bleed pipe from a 2001 or later C5 on the rear ports and ran 1/4" heater hose around to the front. In my case I ran the 1/4" hose past the right valve cover and teed into the front coolant air bleed hose. I also found that for my 2001 car, the 2001 or later front coolant air bleed pipe put in back was too close to the hard auxiliary air pipe behind the manifold, so I cut and partially flared the cut ends and put a 1/4" tee in the rear, then ran the 1/4" heater hose to the front. If you remove that pipe as noted above, that will not be a problem.
Here is a front 2001- later C5 coolant air bleed pipe from EBay:
The next time I have the intake off I will relocate the passenger side auxiliary check valve to the right bank and remove the piping for it behind the manifold so that the valve is easily replaced or serviced in the future. You will need some parts as shown here:
If your car is earlier, it will have the rear "steam ports" (coolant air bleed ports) on the heads connected to the front ports. If not, connecting them to the front ports will make getting the air out of the heads easier on coolant changes and maybe reduce the chances of rear cylinders running hot. Bill Curlee used a front coolant air bleed pipe from a 2001 or later C5 on the rear ports and ran 1/4" heater hose around to the front. In my case I ran the 1/4" hose past the right valve cover and teed into the front coolant air bleed hose. I also found that for my 2001 car, the 2001 or later front coolant air bleed pipe put in back was too close to the hard auxiliary air pipe behind the manifold, so I cut and partially flared the cut ends and put a 1/4" tee in the rear, then ran the 1/4" heater hose to the front. If you remove that pipe as noted above, that will not be a problem.
Here is a front 2001- later C5 coolant air bleed pipe from EBay:
You can also use the rear Vortec truck cross over tube.
The next time I have the intake off I will relocate the passenger side auxiliary check valve to the right bank and remove the piping for it behind the manifold so that the valve is easily replaced or serviced in the future. You will need some parts as shown here:
If your car is earlier, it will have the rear "steam ports" (coolant air bleed ports) on the heads connected to the front ports. If not, connecting them to the front ports will make getting the air out of the heads easier on coolant changes and maybe reduce the chances of rear cylinders running hot. Bill Curlee used a front coolant air bleed pipe from a 2001 or later C5 on the rear ports and ran 1/4" heater hose around to the front. In my case I ran the 1/4" hose past the right valve cover and teed into the front coolant air bleed hose. I also found that for my 2001 car, the 2001 or later front coolant air bleed pipe put in back was too close to the hard auxiliary air pipe behind the manifold, so I cut and partially flared the cut ends and put a 1/4" tee in the rear, then ran the 1/4" heater hose to the front. If you remove that pipe as noted above, that will not be a problem.
Here is a front 2001- later C5 coolant air bleed pipe from EBay:
There is a great YouTube video on the relocation that I used to do the relocation or the check valve.
Pulling Intake Manifold - What maintenance items should I do?
