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Opti vent harness check

3K views 14 replies 6 participants last post by  1slow96 
#1 ·
Im curious if there is a good way to check the opti vent harness more than just visually. My main concern being the one with the check valves. Check valve orientation is one way, allowing vaccum into the opti right or wrong?
Was going to replace put appear fine but figure id make sure everything flowing to right way. Gm replacement is pricy, but if i could make my own that would be cool. Just not fully understanding how the harness works.
 
#2 ·
I know I saw a recent thread on this. Did you try a search on the Forum?
 
#5 ·
on mine the blue part is on the opti side
 
#6 ·
The "blue" side of both valves faces the manifold (away from opti) I cannot overstate the importance of these valves pointing in the right direction. Verify proper ventilation. Either with a vacuum gauge (the best way) proper ventilation is indicated by the gauge slowly raising until manifold vacuum is reached,or with a piece of paper (common,but crude). Many cases of opti failure can be directly linked to ventilation,or lack thereof.
 
#7 ·
Verify proper ventilation. Either with a vacuum gauge (the best way) proper ventilation is indicated by the gauge slowly raising until manifold vacuum is reached,or with a piece of paper (common,but crude). Many cases of opti failure can be directly linked to ventilation,or lack thereof.
are you saying Opti vacumn should read what the manifold vacumn is (18-19 in HG) at the blue nipple that goes into the rubber intake elbow?

Mine reads 4 at that point. It reads 18-19 on the hose that has the blue valves that plugs into bottom of Opti
 
#8 ·
Yes,or at least close to it. I've heard of cleaning the check valves with alcohol (not on the car) you may have a vacuum leak in the check valve,or more likely where the hose meets nipple. Check hose snugness at the opti itself. New lines aren't that expensive,get "fuel injection" line if possible. It holds up much better. At least cut 1/2" off each end of the existing lines,for more secure connections if you aren't prepared to swap out the lines.
 
#9 · (Edited)
The blue nipple on vent hose does not have check valves. It runs straight to Opti. That line reads 4 in vac. The line with the check valves reads 18

This is a brand new vent harness, GM

The line that goes to the blue nipple fits the metal nipple on Opti and the line that goes to manifold has 2 check valves and goes to the larger "plastic" nipple on the Opti.

also this is a comment from Rocko about opti vent vacumn

"The disc looking thing in the opti harness is a vacuum limiter. designed to limit the vacuum to around 4inches i believe. It does need to be able to hold a small piece of paper. "
 
#10 ·
All this is in the FSM. I want to help,but I'm weary of the endless debating about every little thing that this forum has become. If the vacuum was limited,then how could you have 18in. at the opti ,but the line with nothing on somehow reads 4in. If you've checked that line for a leak,then the only thing that occurs to me is that the opti itself is no longer sealed.
 
#11 · (Edited)
1Slow..

appreciate your comments and yes if the vacumn reading at bottom of line with blue valves is 18 and if only 4 on the nipple at intake elbow that suggests the "Opti" itself is not sealing

I will search my FSM to see wtf it has to say about checking and if 18 in of vacumn is what we should be reading from the blue nipple and not 4.


Also it appears the blue/white valves are not "restrictors" but directional meaning they only allow fow one direction, right?

maybe you or someone who has a vacumn gauge can check wtf their vacumn is at blue nipple with hole in intake elbow plugged??
 
#14 ·
I will search my FSM to see wtf it has to say about checking and if 18 in of vacumn is what we should be reading from the blue nipple and not 4.


??
FWIW I did look in the FSM "Distributor Ventalation System" 6D4-7 &8. While it does not give specific vacumn" specs it states vacumn at blue nipple on "duck, air intake" should slowly build and = manifold vacumn.

Mine does not as it goes to 4" not 18"-19".

It would appear the brand new Delphi Opti does not seal very well. I did remove cap to put loc-tite on rotor screws and replaced. Maybe it needs some form of "sealant"

or is there opinions that 4" is enough vacumn to purge moisture and gasses?

I do know a non functioning vent harness will kill Optis in as few as 500 miles as the dealer replaced 3 in a row back when my car was under warrenty....I later discovered a blue/white valve was reversed by Mr Goodwrench. I bought the car back to the dealer, they removed Opti and green crud flowed out. Have not had the problem since check valves are in correct position

I am chasing a stumble under load problem and after replacing opti, vent harness, plugs, wires, ICM, coil, injectors, MAF, MAP, EGR & solonoid the problem still persists......wondering if the possible 'leaking" vacumn through Opti is the culpret??

Either case I will have to pull Opti just to seal it to hold vacumn before crud builds up in it.
 
#12 ·
My understanding about the blue/white valves is they control direction,and rate of flow. They also control how quickly the vacuum inside the opti goes up,and down as compared to vacuum inside the intake manifold itself. They are both important,the most common problem seems to be putting one of them in backwards.This will ultimately lead to an opti failure.
 
#15 ·
Seems to me the vent. harness pulls the same amount of air into the intake regardless if the opti leaks or not. I wouldn't open up a new opti just to put loc-tite on the rotor screws,but that's me. I will do that if I've got one apart. Some like using RTV, dielectric grease seem just as effective to me. A little bit on the seals should do the trick.
 
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