Secondary Port Throttle Actuator vacuum leak

[boostedmaxPSI]

Guys,

Something had been gnawing on me about the condition of the secondaries and how well they were working. I had addressed the vacuum leaks but I always felt something was fully opening/working.

So.... off comes the plenum again, for additional testing for peace of mind.

This time I hooked up a vacuum gage inline so I could see how much vacuum was being lost when I backprobed pin C17 to activate the secondaries.

First thing I noticed was the driver side secondary ports were fully open and the passenger side ports were only opening part way. In addition to the passenger ports not opening all the way, my vacuum gauge would drop below 5" and the driver side actuator would start to close partly.

I isolated the problem to the passenger actuator itself. Please see the attached video:

http://www.youtube.com/watch?v=yjtZAtr3fF4&feature=youtu.be

Notice how the vacuum starts to bleed off almost instantly. This does not happen to the driver side actuator however, the passenger side actuator will hold vacuum when you go above 15" vacuum. I assume this is because the internal diaphragm is laying over itself and sealing the internal leak.

Another observation is how the diaphragm pulls in at an odd angle. Seems like something is not centered internally to the actuator.

Thoughts?

I plan on purchasing two new GM units tomorrow. Who do you recommend that I source these parts from?

thanks
Frank

[Z51JEFF]

Guys,

Something had been gnawing on me about the condition of the secondaries and how well they were working. I had addressed the vacuum leaks but I always felt something was fully opening/working.

So.... off comes the plenum again, for additional testing for peace of mind.

This time I hooked up a vacuum gage inline so I could see how much vacuum was being lost when I backprobed pin C17 to activate the secondaries.

First thing I noticed was the driver side secondary ports were fully open and the passenger side ports were only opening part way. In addition to the passenger ports not opening all the way, my vacuum gauge would drop below 5" and the driver side actuator would start to close partly.

I isolated the problem to the passenger actuator itself. Please see the attached video:

http://www.youtube.com/watch?v=yjtZAtr3fF4&feature=youtu.be

Notice how the vacuum starts to bleed off almost instantly. This does not happen to the driver side actuator however, the passenger side actuator will hold vacuum when you go above 15" vacuum. I assume this is because the internal diaphragm is laying over itself and sealing the internal leak.

Another observation is how the diaphragm pulls in at an odd angle. Seems like something is not centered internally to the actuator.

Thoughts?
I plan on purchasing two new GM units tomorrow. Who do you recommend that I source these parts from?

thanks
Frank

Id check with Jerrys Gaskets first.

[GOLDCYLON]

I have a used pair of vaccum actuators that I no longer need they were purchased from Tom Henry Chevrolet in early 2011. Hows $100 for the pair plus shipping sound? I paid $125 each for these but they are one year used. Lmk. GC

[GOLDCYLON]

These pull at an unnatural angle as designed by GM. If they lengthed and centered the rod it would have been a better design. I am sending you a pic of mine attached to the actuator rod when we pulled them out of the car.


http://i1120.photobucket.com/albums/l498/goldcylon/ACT2.jpg?t=1335128824

http://i1120.photobucket.com/albums/l498/goldcylon/ACT1.jpg?t=1335128969

[A26B]

The actuator actually pulls straight with the "angled linkage" installation. If you turn it over & make the linkage "straight", the diaphram will pull at an angle, resulting in binding. FOr best operation, leave the actuator angled, the way it originally & intentionally came from MerCruiser.

Good pictures Daryll.

[GOLDCYLON]

The actuator actually pulls straight with the "angled linkage" installation. If you turn it over & make the linkage "straight", the diaphram will pull at an angle, resulting in binding. FOr best operation, leave the actuator angled, the way it originally & intentionally came from MerCruiser.

Good pictures Daryll.


True statement.

[boostedmaxPSI]

I have a used pair of vaccum actuators that I no longer need they were purchased from Tom Henry Chevrolet in early 2011. Hows $100 for the pair plus shipping sound? I paid $125 each for these but they are one year used. Lmk. GC

When you apply vacuum to these units how does the center rod get pulled in? Did you notice in the video that I posted how the rod will make contact to the housing? I assume there is something off internally.

[GOLDCYLON]

When you apply vacuum to these units how does the center rod get pulled in? Did you notice in the video that I posted how the rod will make contact to the housing? I assume there is something off internally.

Correct it should not slap the housing as demonstrated in your video. They will slightly graze the edges somewhat center and hold vaccum. All these are are vaccum diaphrams when they age and wear they leak and set a CODE 61. We have all been there and done that.

[XfireZ51]

I got an idea! Pull the throttle plates on the secondaries and we'll throw in a chip that has secondary injectors turn on at anything above idle. You can unplug the secondary MAP sensor and air pump.

[Z51JEFF]

Daryll,Ill take these if the OP passes.

[GOLDCYLON]

Daryll,Ill take these if the OP passes.


Jeff I shipped them already. I have another pair but they are not almost new like these were.

[Paul Workman]

I got an idea! Pull the throttle plates on the secondaries and we'll throw in a chip that has secondary injectors turn on at anything above idle. You can unplug the secondary MAP sensor and air pump.

Yep! Parts not used seldom fail, and they don't cost anything to replace!

OP: Like most of us that have pulled the secondaries, they haven't given me a lick of trouble since. AND, I like the crisp throttle response, and the clean intake valves!:thumbsup:

P.

[boostedmaxPSI]

Took apart the Secondary Actuator to see if my suspicion was correct and it was. The internal spring was not centered causing some binding. the point where the smaller end of the spring that meets the center point of the base was not opened up enought to fully seat around the base point.

I opened the spring up just a bit to see what would happen and the spring stays where it should be, centered.

I'm going to attempt to put this one back together to see if the condition improves. I have nothing to loose given two are on the way.

Base of the spring too small (before modifing the spring)

http://inlinethumb29.webshots.com/50460/2719854790081718910S500x500Q85.jpg


Spring not centered. This is how the spring was situated when I pulled actuator apart.

http://inlinethumb18.webshots.com/49617/2580142310081718910S500x500Q85.jpg


This is with the spring opened up a bit more so it could fully seat around the base and stay centered.

http://inlinethumb64.webshots.com/2623/2430923250081718910S500x500Q85.jpg

[scottfab]

Frank I applaud your decision to stay with the stock setup.
Long term value could well be in how close you stay stock.
(or returnable to stock)
Remembering back I think it was Mark H. that found a lot
of actuators coming from the GM dealership that were defective
in the same way you're seeing.

About 10yrs ago I developed a replacement idea using electrically operated solenoids. I have them still and the brackets for mounting. All that remained was working out where to tie into the electronics which will be trivial once the need arises.
And there in lies the catch. My secondaries have not failed since I worked on them in 99. Once they do begin to act up again I intend to swap out the actuators. This will be reversible and will not require a chip mod which in itself is a potential maintenance issue. (replacement parts)

Good luck with the new parts.

[GOLDCYLON]

Took apart the Secondary Actuator to see if my suspicion was correct and it was. The internal spring was not centered causing some binding. the point where the smaller end of the spring that meets the center point of the base was not opened up enought to fully seat around the base point.

I opened the spring up just a bit to see what would happen and the spring stays where it should be, centered.

I'm going to attempt to put this one back together to see if the condition improves. I have nothing to loose given two are on the way.

Base of the spring too small (before modifing the spring)

http://inlinethumb29.webshots.com/50460/2719854790081718910S500x500Q85.jpg


Spring not centered. This is how the spring was situated when I pulled actuator apart.

http://inlinethumb18.webshots.com/49617/2580142310081718910S500x500Q85.jpg


This is with the spring opened up a bit more so it could fully seat around the base and stay centered.

http://inlinethumb64.webshots.com/2623/2430923250081718910S500x500Q85.jpg


Never seen one of these apart before. Cool pics.

[boostedmaxPSI]

UPDATE:

So with nothing to loose, I was able to correct the spring location by widening the spring base a bit and track down a very small pin hole leak. Sealed the leak and put it back together.

IT WORKS. check the video out. The actuator will now hold vacuum with as little as one pump on the vacuum gun.

http://www.youtube.com/watch?v=MlkNWBNtaYo


Question:

What is the correct orientation for the actuator arm. Notice the slight angle. Does the angle point to the center of the engine or to the IH?

http://inlinethumb29.webshots.com/18524/2867630300081718910S600x600Q85.jpg

[scottfab]

I looked at my photo archives and can't find what I'm looking for.
However this was the source of a lot of exchanges on the ZR1Net mail list
years ago. There were many actuators that were mounted upside down.
Thing is without the pics I can't tell which way it should be.

[boostedmaxPSI]

I looked at my photo archives and can't find what I'm looking for.
However this was the source of a lot of exchanges on the ZR1Net mail list
years ago. There were many actuators that were mounted upside down.
Thing is without the pics I can't tell which way it should be.

Thanks for looking Scott. The actuator arm with the slight angle, is mounted with the angle towards the IH.

Frank