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=yjtZA...ature=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]

Originally Posted by 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=yjtZA...ature=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.

[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]

Originally Posted by 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.

True statement.

[boostedmaxPSI]

Originally Posted by 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

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]

Originally Posted by boostedmaxPSI

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.