Finding my vacuum leak...

[Billy Mild]

I have made a few threads about my intermittent vacuum leak. It seems to be almost 100% temperature related. I pulled the plenum today to replace my coil packs(dealing with a random misfire), while I was in there I decided to take a look at the vacuum leak. I got my mityvac out and started pulling some vacuum. I think I have tracked it down to a failed vacuum switch.

Below is the picture of the piece and where its located.

http://i856.photobucket.com/albums/ab123/billymild/zr1/IMG_20150315_163653_zpszvhfbhes.jpg

http://i856.photobucket.com/albums/ab123/billymild/zr1/IMG_20150315_163702_zpsiuigajzk.jpg


VIDEO:
http://i856.photobucket.com/albums/ab123/billymild/zr1/th_VID_20150315_163837_zpsritu5yq9.mp4 (http://i856.photobucket.com/albums/ab123/billymild/zr1/VID_20150315_163837_zpsritu5yq9.mp4)

Any help is appreciated.

[mgbrv8]

If you want to see whats inside heres what it looks like

https://www.facebook.com/photo.php?fbid=10201127223849592&set=a.10201021415884459.2217036.1439230280&type=3&theater

I found these parts way cheaper by researching the part numbers and finding their other applications Ex. the VACUUM AMPLIFIER RESERVOIR is from a 77 f150 ford and for the truck its only $16 at orillys

https://www.facebook.com/photo.php?fbid=10205967051362255&set=p.10205967051362255&type=1&theater

here is the full plenum pull photo Album

https://www.facebook.com/media/set/?set=a.10201021415884459.2217036.1439230280&type=1&l=8f46fa4533

[Billy Mild]

The reservoir is fine.

http://www.jerrysgaskets.com/valve-vacuum-in-line-check-90-95-8c2/

This is the piece I think is not working correctly.

[mgbrv8]

Thats the neat thing the check valve in the lid looks just like the gm one. I couldn't get over how much dirt was in there. Makes u wonder if that dirt over time will damage any valve installed in line?? Hmm

Dave Hetrick

[Kevin]

That maybe my problem too

[mgbrv8]

Maybe Kevin this is how much dirt that was in the after 70k miles. The car was pampered all its life Im the first owner to drive it in the rain .

Here is a pic of the crud in the container

https://www.facebook.com/photo.php?fbid=10201127224689613&set=a.10201021415884459.2217036.1439230280&type=3&permPage=1

[Dynomite]

The Vacuum Check Valve isolates Vacuum Pump vacuum when Plenum Vacuum is low (WOT for example or when engine is not running but key is on). The check valve closes such that the Drivers side Plenum Vacuum source between the two Plenum Runners is closed when Plenum Vacuum is low.

When the engine is not running but ignition switch is on (Vacuum Pump running) the Plenum Vacuum is Zero (similar to WOT). A failed Vacuum Check Valve fails to close such that the vacuum pump keeps cycling sucking air from the plenum having no vacuum.

The test of that Vacuum Check Valve is a simple test without removing the Plenum. Just disconnect the Plenum Vacuum line on the drivers side and hold thumb over end of disconnected line. With the Ignition Switch on the Vacuum Pump will keep cycling until you plug the end of that vacuum line fitting. The Vacuum Pump will then stop cycling indicating no Vacuum leaks unless of course you have additional Vacuum leaks in the Secondary Vacuum System. If disconnecting that Vacuum line results in the Vacuum Pump not Cycling without blocking with finger, the Vacuum Check Valve is operating correctly. The Plenum has to be removed to replace that check valve.

See Item #3 Finding A Vacuum Leak (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-7.html#post1584987830)

[Billy Mild]

Dynomite, thanks for the response. Looks like I need to get a new check valve. This one has failed.

[Billy Mild]

Could the check valve be backwards?

[Mystic ZR-1]

PN for the check valve?
PN for the secondary port throttle valve solenoid too?
GM, NAPA, Advanced Auto Parts etc. to locally source.
These parts must have lots of different applications?
Thanks!

[Billy Mild]

Check Valve: 14047619

[cvette98pacecar]

Could the check valve be backwards?

Your secondaries wouldnt open if it was backwards.

[Billy Mild]

Do I have the check valve in the right direction?

[Billy Mild]

Wrapping up my final plenum pull, I have fixed all the vacuum leaks. The check valve was my intermittent vacuum leak. When warm occasionally it would seal up otherwise it wouldn't. I cleaned the IAC, TB, and plenum. I tried to lubricate the TB plates and shaft with lithium grease. This didn't help the issue either.

I still have a hanging idle issue occasionally. If i stab the throttle idle goes back to normal every time.

Does that mean something is wrong with TB itself?

[Paul Workman]

Wrapping up my final plenum pull, I have fixed all the vacuum leaks. The check valve was my intermittent vacuum leak. When warm occasionally it would seal up otherwise it wouldn't. I cleaned the IAC, TB, and plenum. I tried to lubricate the TB plates and shaft with lithium grease. This didn't help the issue either.

There is some "DAG" compound in the TB bores that aids in sealing the main throttle plates. If you cleaned that out, you may well have the source of your high idle issue! Did you clean out the TB bores - most especially the location where the main tB plates rest against the TB at idle?


I still have a hanging idle issue occasionally. If i when the throttle idle goes back to normal. Does that mean something is wrong with TB itself?

Well... I dunno whatcha are trying ta "axe" here?:confused:

[Billy Mild]

Edited my last post. Thats what happens after a few adult beverages and auto correct...