Finding my vacuum leak... - ZR-1 Net Registry Forums

Billy Mild · 03-15-2015

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.

VIDEO:

Any help is appreciated.

mgbrv8 · 03-15-2015

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

https://www.facebook.com/photo.php?f...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?f...type=1&theater

here is the full plenum pull photo Album

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

Billy Mild · 03-15-2015

The reservoir is fine.

http://www.jerrysgaskets.com/valve-v...eck-90-95-8c2/

This is the piece I think is not working correctly.

mgbrv8 · 03-15-2015

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 · 03-15-2015

That maybe my problem too

mgbrv8 · 03-15-2015

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?f...e=3&permPage=1

Dynomite · 03-15-2015

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

Billy Mild · 03-16-2015

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

Billy Mild · 03-16-2015

Could the check valve be backwards?

Mystic ZR-1 · 03-16-2015

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!

03-15-2015	#1
Billy Mild Join Date: Aug 2014 Location: Kansas City, MO Posts: 838	Finding my vacuum leak... 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. VIDEO: Any help is appreciated. __________________ Looking for a ZR-1 1985 Yamaha RZ350-NOT STOCK 1971 Yamaha AT1-Middle of a restoration

03-15-2015	#2
mgbrv8 Join Date: Jul 2009 Location: Texas Posts: 793	Re: Finding my vacuum leak... If you want to see whats inside heres what it looks like https://www.facebook.com/photo.php?f...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?f...type=1&theater here is the full plenum pull photo Album https://www.facebook.com/media/set/?...1&l=8f46fa4533

03-15-2015	#4
mgbrv8 Join Date: Jul 2009 Location: Texas Posts: 793	Re: Finding my vacuum leak... 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

03-15-2015	#5
Kevin Join Date: Jun 2005 Location: pittsburgh Posts: 4,632	Re: Finding my vacuum leak... That maybe my problem too __________________ It's not the car, it's the people - Doug Johnson 90 r/r "KEYS ON" nick named "T.L.B"

03-15-2015	#6
mgbrv8 Join Date: Jul 2009 Location: Texas Posts: 793	Re: Finding my vacuum leak... 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?f...e=3&permPage=1

03-15-2015	#3
Billy Mild Join Date: Aug 2014 Location: Kansas City, MO Posts: 838	Re: Finding my vacuum leak... The reservoir is fine. http://www.jerrysgaskets.com/valve-v...eck-90-95-8c2/ This is the piece I think is not working correctly. __________________ Looking for a ZR-1 1985 Yamaha RZ350-NOT STOCK 1971 Yamaha AT1-Middle of a restoration

03-15-2015	#7
Dynomite Join Date: Aug 2009 Location: South Dakota/California Posts: 3,797	Vacuum Check Valve 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 __________________ Left Clickable links -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 03-15-2015 at 11:44 PM.

03-16-2015	#8
Billy Mild Join Date: Aug 2014 Location: Kansas City, MO Posts: 838	Re: Finding my vacuum leak... Dynomite, thanks for the response. Looks like I need to get a new check valve. This one has failed. __________________ Looking for a ZR-1 1985 Yamaha RZ350-NOT STOCK 1971 Yamaha AT1-Middle of a restoration

03-16-2015	#9
Billy Mild Join Date: Aug 2014 Location: Kansas City, MO Posts: 838	Re: Finding my vacuum leak... Could the check valve be backwards? __________________ Looking for a ZR-1 1985 Yamaha RZ350-NOT STOCK 1971 Yamaha AT1-Middle of a restoration

03-16-2015	#10
Mystic ZR-1 Join Date: Jan 2010 Location: Mystic CT Posts: 2,627	Re: Finding my vacuum leak... 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!