Need help with vacuum leak

[detch]

Need help with a vacuum leak, when I turn on the car but not start it the pump keep running, when I pull the one hose off the driver side of the plenum and plug it the pump stops. I tried to pull a vacuum on the plenum's connector but it won't hold a vacuum. any ideas?

thanks
Mike :icon_scra

[LGAFF]

Are you testing vac off the P/S that is running from near the coolant overflow into the plenum? You should be able to hold vac if you plug your vac tester into the line running to the plenum. It should hold with slow leakdown at least.

If not there is a good chance you have a leak under the plenum.

LGAFF
92 ZR1
#234

[tomtom72]

If you can't hold any vacuum on the plenum side of the line you could see if you can find a vacuum check valve that fits the connector. Plug it into the line going under the plenum and re-do the vac test. If you hold vacuum upon the retest then you have solved the issue. There is a vacuum check valve in the hose network under the plenum that could have given up the ghost.

If that new check valve does not help, then the 2* control solenoid, reserve storage tank, maybe even the actuators or a leak in the actual hose are likely suspects. Unless you are setting a DTC61, I would say that the actuators are okay. To get an eyeball on what is under the plenum use this link.

http://www.corvetteactioncenter.com/forums/showthread.php?t=14272

some great stuff that gives a great explaination.

:cheers:

[detch]

the vacuum is from the electric vacuum pump in the fron passanger side of the car. I check the hose from the check valve to the pump and they are fine, I wanted to check the connections on the outside of the plenum, when I remove the hose from the manifold vacuum (6e3-c2-6 fig c2-7 block #2) in service manual and pluged it, the moter stops, so I think the leak is between this connector on the plenum and where ever it goes, I just don't know where it goes.
I not talking from the connector to the check valve under the plenum I talking the other way from the connector on the plenum into the plenum

:dontknow:

Mike

[Jeffvette]

the vacuum is from the electric vacuum pump in the fron passanger side of the car. I check the hose from the check valve to the pump and they are fine, I wanted to check the connections on the outside of the plenum, when I remove the hose from the manifold vacuum (6e3-c2-6 fig c2-7 block #2) in service manual and pluged it, the moter stops, so I think the leak is between this connector on the plenum and where ever it goes, I just don't know where it goes.
I not talking from the connector to the check valve under the plenum I talking the other way from the connector on the plenum into the plenum

:dontknow:

Mike

From the driver side port, the line goes into a check valve, then from there goes directly into a "T" port on the line. The two other sections of the "T", 1 goes to the vacuum pump, the other goes to the vacuum reservoir.

[rhipsher]

Check valves don't give up the ghost. They just get dirty and clogged. There are actually two check valves under the plenum. One in the front and one in the back. Easy way to check it is to unhook it and block the single perpendicullar outlet with your finger and blow through the other two ends. It should only allow air flow in one direction. If you are able to blow air through in both directions then its got dirt in it. All there is is a little bee bee ball inside of it. Just take some carburator cleaner and spray it in all the outlets. Then blow it dry. Then take some WD40 and also spray it in all the outlets. Check valve will be as good as new. But hell what do I know. Also when it comes to secondary port throttle failure be suspicious of the secondary vacume solenoid. It has a little cheesy air filter on it and over the years will evetually get old and turn to dust allowing contaminents to get sucked up into it and cause it to fail giving you that "Run out of breath at 4000rpm''s old man caugh under hard acceleration (SES light)error code 61 BS".

[Jeffvette]

Check valves don't give up the ghost. They just get dirty and clogged. There are actually two check valves under the plenum.


Two check valves, only one is causing an issue with the secondary operation. One for the cruise and one for the secondary system.

[rhipsher]

Just stating the fact that there are two check valves under there. I never said they both affected the secondary vacum operation. But while he's under there he might as well clean both of them. Unless you never use cruise control. But since you are more of a ZR-1 genius than me you can help him out. I'll just stay out of it. Why should I care, as long as mine runs fine. Right!:bootyshak Sorry detch I hope you figure it out soon. Jeffvette should be able to get you all fixed up and running. I'll just mind my own business next time somebody needs help.

[Jeffvette]

Just stating the fact that there are two check valves under there. I never said they both affected the secondary vacum operation. But while he's under there he might as well clean both of them. Unless you never use cruise control. But since you are more of a ZR-1 genius than me you can help him out. I'll just stay out of it. Why should I care, as long as mine runs fine. Right!:bootyshak Sorry detch I hope you figure it out soon. Jeffvette should be able to get you all fixed up and running. I'll just mind my own business next time somebody needs help.


Whoa....... I just didn't want him poking around looking for a second check valve on the secondary system. I've seen people mention problems on a 90, which has a few different systems and people with later cars suggesting to check this piece, which the 90 doesn't have. The more info the better. :thumbsup:

[65ZR1]

Wow, I think someone needs more sleep!

[rhipsher]

Sorry Jeff. Just had a lousy day at work yesterday. Didn't mean to snap at you. My apologies.:handshak:

[Jeffvette]

Sorry Jeff. Just had a lousy day at work yesterday. Didn't mean to snap at you. My apologies.:handshak:


No worries dude

[detch]

Well, I puilled the plenum and cheched the connections and found a loose one connection at the T. I put it all back together and the vac pump keeps running.
I pulled the the connector off at the plenum on the driver side and plug it and the vacuume pump stopped. I put it back on plenum and it started running again. :censored:
any ideas?
Will this prevent the secondaries from operating (no full power)?
What would happen if I just plugged the connector and did not connect it to the connector on the plenum?

thanks
Mike

[tccrab]

Well, I puilled the plenum and cheched the connections and found a loose one connection at the T. I put it all back together and the vac pump keeps running.
I pulled the the connector off at the plenum on the driver side and plug it and the vacuume pump stopped. I put it back on plenum and it started running again. :censored:
any ideas?
Will this prevent the secondaries from operating (no full power)?
What would happen if I just plugged the connector and did not connect it to the connector on the plenum?

thanks
Mike

Mike:

A bad check valve?
Hmmm..
Gonna go dig out my FSM...

Your '95 is a little different under the plenum than my '90, but they work the same. There is a check valve (item #15 pg 6A2A-33 LT5 Service Manual Supplement) located inline with that hose which is connected to the plenum. If that check valve is breached, it will allow the vacuum pump to suck air past the valve and cause the vacuum pump to run continuously.
If I read the diagram correctly, the check valve allows the vacuum pump to pull a vacuum on the secondary system until the engine starts producing suitable vacuum. When the magic pressure is reached, the check valve opens and the ECM directs the vacuum pump to stop.

I'm just guessing, but if you were to plug this line it's possible that the secondaries might not have enough vacuum to:
A: open the secondaries completely, or;
B: hold them open for any appreciable lenght of time.

TomC
'Crabs"

[detch]

Bad check valve was it, all fixed.
thanks all for the help

Mike

!:cheers:

[tomtom72]

:thumbsup: Good deal Mike! Now go play with the toy!:mrgreen:

[RJC061500]

This is my first post on this site, and first I would like to thank everyone for the great information posted. I am in the process of changing injectors on my 90. I have everything ready to go, however, I’m chasing a vacuum leak. On the passenger side I can plug the pump and it will shut off. Also have vacuum up to the Vacuum Solenoid, which I just replaced. I made a filter out of hose and wax applicator (As I learned on this site.) I also blew into the vacuum line near the check valve and it one side did not allow air to pass (Also learned from this site.) Now when I test the pump, it cycles on and off every few seconds. I can block the vacuum line on the drier side, mid plenum and the pump stops. My questions are:
1: Could the check valve be clogged even though I could only blow air through one side?
2. If the check valve is the cause of the problem, is it better to clean the check valve with carb cleaner or replace it with an aftermarket one?
3: And finally, if I should replace the check valve, how to I get the factory one disconnected from the vacuum lines?
Sorry for so many questions, but I’m afraid to cause damage to the vacuum lines trying to replace the valve.

Thanks in advance for any replies to this post.

[Hammer]

If you pulled the hose off the driver's side of the plenum (about the middle) and the pump stopped, it's the check valve...you can still get them from the dealer. But, I replaced one under both cars and they both ahve since failed. BS.

I rigged up a little loop for outside. After market check valve from any auto parts store that has them, two rubber lines, different sizes and a reducer fitting and both are fine now. The only check valves I have seen available are different sizes in and out.

I don't know why these valves last for 18-20 years and then you replace them and they go kapoot in two months. But mine did.

[rhipsher]

If you pulled the hose off the driver's side of the plenum (about the middle) and the pump stopped, it's the check valve...you can still get them from the dealer. But, I replaced one under both cars and they both ahve since failed. BS.

I rigged up a little loop for outside. After market check valve from any auto parts store that has them, two rubber lines, different sizes and a reducer fitting and both are fine now. The only check valves I have seen available are different sizes in and out.

I don't know why these valves last for 18-20 years and then you replace them and they go kapoot in two months. But mine did. Just like I said way back when this thread was started Just clean it with carb cleaner or break clean and blow out with air and spray WD40 in it. It will be good as new and last another 18 years. Trust me on this. All it takes is a little dirt to get on that little bee bee ball inside of it.

[secondchance]

This is my first post on this site, and first I would like to thank everyone for the great information posted. I am in the process of changing injectors on my 90. I have everything ready to go, however, I’m chasing a vacuum leak. On the passenger side I can plug the pump and it will shut off. Also have vacuum up to the Vacuum Solenoid, which I just replaced. I made a filter out of hose and wax applicator (As I learned on this site.) I also blew into the vacuum line near the check valve and it one side did not allow air to pass (Also learned from this site.) Now when I test the pump, it cycles on and off every few seconds. I can block the vacuum line on the drier side, mid plenum and the pump stops. My questions are:
1: Could the check valve be clogged even though I could only blow air through one side?
2. If the check valve is the cause of the problem, is it better to clean the check valve with carb cleaner or replace it with an aftermarket one?
3: And finally, if I should replace the check valve, how to I get the factory one disconnected from the vacuum lines?
Sorry for so many questions, but I’m afraid to cause damage to the vacuum lines trying to replace the valve.

Thanks in advance for any replies to this post.

Welcome to the Forum!

Answers:
1. No. These are 3 way check valve. You should not be able to blow into single large side. 2 smaller side, closing one or the other, you should be able to blow through it.
2. Replace. Less than $5 at dealership. On 94 there are 2 check valves (pretty sure 90 have 2 also).
3. They pull of from vacuum lines (twist first since time and heat may have sort of fused them).

If you get some leak, check all rubber fittings to hard vacuum lines. You may find some loose connections. If you do, use high temp sealant and small zip-ties to seal them.

Hand held vacuum pump is helpful in tracking fitting to fitting and locating leaks.

Good luck!:hello:

[secondchance]

If you pulled the hose off the driver's side of the plenum (about the middle) and the pump stopped, it's the check valve...you can still get them from the dealer. But, I replaced one under both cars and they both ahve since failed. BS.

I rigged up a little loop for outside. After market check valve from any auto parts store that has them, two rubber lines, different sizes and a reducer fitting and both are fine now. The only check valves I have seen available are different sizes in and out.

I don't know why these valves last for 18-20 years and then you replace them and they go kapoot in two months. But mine did.

Last time i pulled the plenum I replaced both check valves, confirmed vacuum pump was holding, buttoned everything up and ran the motor for a while. The next morning, dreaded vacuum pump keeps running syndrom came back. So, pulled the plenum, found check valve blowing both ways, replace, button up and same thing!
Playing with what I thought was a defective check valve, I got it to function properly again!
I realized there must have been small debris somewhere in the system. So, I went out and drove the car like a mad man for a while until engine vacuum sucked and cleared all debris. Since then I have no more vacuum issues.
I am not saying you have the same situation but just in case...:cheers:

[Paul Workman]

Just take some carburator cleaner and spray it in all the outlets. Then blow it dry. Then take some WD40...

I wuz with ya up to the "WD40" part. "WD" is some great stuff, but I can assure ya it will get gummy in time (accelerated by heat) - tries to become varnish(?), I guess. And! It attracts dust.

I've had good luck on other small metal parts using silicone spray, after a good cleaning with a degreaser to first remove the oil. But, I'm not a chemist, and perhaps one that is can make a suggestion?

Just a personal observation; I would definitely stay away from the tri or tetra-chloride type brake cleaners tho. It is great stuff, but I can tell ya that stuff will attack certain types of plastic with a vengeance - becoming a gooey mess! The carb cleaner may be fine, but again I ain't no chemist!

P.

[rhipsher]

I wuz with ya up to the "WD40" part. "WD" is some great stuff, but I can assure ya it will get gummy in time (accelerated by heat) - tries to become varnish(?), I guess. And! It attracts dust.

I've had good luck on other small metal parts using silicone spray, after a good cleaning with a degreaser to first remove the oil. But, I'm not a chemist, and perhaps one that is can make a suggestion?

Just a personal observation; I would definitely stay away from the tri or tetra-chloride type brake cleaners tho. It is great stuff, but I can tell ya that stuff will attack certain types of plastic with a vengeance - becoming a gooey mess! The carb cleaner may be fine, but again I ain't no chemist!

P.
I made sure when I did it that I blew most of the WD40 out with compressed air. Its been 2 1/2 years since and have had no problems.
Acrylic type plastics are what you don't want to use acetone or break clean on cuz they will melt. The check valves are made of black delrin so it's safe to use on them. I learned this lesson the hard way on time. I was machining some parts out of acrylic with tolorences of +.0005 -.0000. I filled a little tub with acetone to throw the parts in after they came off the machine and I was humming right along. Then I turned around to blow the parts off I had spent all morning making and they were gone. I thought where did my parts go? I stuck my finger down in the tub of acetone and there was a sludge down in the bottom. The parts had completely melted into a clear sludge. Lexan, black or white delrin and teflon is not affected. But fiberglass or acrylic is.

[RJC061500]

Just finished with the injector replacement and finding the vacuum leak. I also had to adjust one of the secondary throttle blades. Turned out the rubber fitting going into the secondary actuator valve could not hold vacuum and I had to replace with aftermarket ones for pep boys. Thanks to everyone who replied to my post I could not have fixed the problem with your assistance. The knowledge of the members of this forum is terrific.

[XfireZ51]

Just get rid of the secondaries. :-D :wave:

[Z51JEFF]

See anything in here that helps?http://i10.photobucket.com/albums/a136/FLYTYM/IMG_0023-2.jpg