Vacuum leaks

[cuisinartvette]

As I was browsing the "Buying a Zr-1" I stumbled across this:
Check for a vacuum leak. Open hood, turn ignition key on but don't start the car. Listen for vacuum pump to come on which is located under front right headlight. It should come on only for a few seconds and turn off. If pump stays on or comes on every few seconds then you have a vacuum leak.

I noticed (with the key on and the engine off) an intermittent noise coming from under the pass.side headlight while waxing the car (90). It would come on a few times per minute, a second or two at a time. Secondaries and lines were replaced before I bought it. Could I have a vacuum leak? Car runs fine, no problems that i can tell.

[Aurora40]

How often is it? I'd think if it were like 30 seconds or more that this might be normalish? That's the secondary vacuum pump, though. Mine comes on for an instant about every 3 seconds... definitely leaking.

[cuisinartvette]

I'll check after work today;hope not, don't want to tear into it just yet.I'll post what I find tonight

[Z Factor]

So did you determine how often it comes on?
As was said it will cycle on now and then, but if you have it going every 15 seconds or so, it has a leak.

:cheers:

[cuisinartvette]

I haven't had a chance to check it, put it back in storage for the time being. I'll check it at some point this weekend, have to go get my stare on :mrgreen:

[Scoob]

I just checked mine...it cycles every 35 seconds with the key on and motor off.

[WB9MCW]

CAV looks like ur ok per scoob's check!!! good to go!!! :o

[cuisinartvette]

I'll check into it Sunday, let you know what I find. Thanks, Scoob!

[Scoob]

I'll check into it Sunday, let you know what I find. Thanks, Scoob!
I think over 25 seconds is good. When I first got mine it was cycling every 10 seconds or so. If you do have a leak it's not a panic situation but should be addressed. Just be sure to get all the parts you need (lines, gaskets)before you pull the plenum.

[Nick]

I replaced all of the vacuum hoses under the plenum of my '94 last year. My pump barely comes on at all, and the car runs great.

[cuisinartvette]

Ok, after coming back from a long drive, I parked it and shut it off. Withthe key in the ON position, I heard from the front pass. side what I'm assuming was the pump ecery 10 seocnds or so. The pump was on for a fraction of a second. Did that twice-Was kind of in a hurry so I didn'y check it with the motor running. I should have a minute or two tomorrow to go play with it some more.

Also, is it common for the doorlock mechanisms to get sticky? Keyless wasn't opening them. You can hear it, but they don't go. Got inside, flipped the lock switch back and forth a 1/2 dozen times and they freed up. Went to lock it with keyless, same thing. Is this an easy fix or am I buying something?

Gotta say, this thing is an animal at sea level. Nice beach cruise today, car performed flawlessly! :thumbsup:

[Nick]

Sounds like you have a small vacuum leak. And yes, these cars LOVE nice, cool, dense sea level air! :cool:

[cuisinartvette]

I don't even know where to start looking! All the vacuum lines and secondary parts (I'm pretty sure) were replaced along with the coils before I bought the car. I'll spend more time on it tomorrow and get back to you guys.

[tomtom72]

Hi Cuisinartvette, There is an article in the "how to" section of the ZR-1 Net Registry. Or you can go to Corvette Action Center.com and look in the C4 / ZR-1 section, it's a sticky I believe. Some useful info there that might help you figure if the leak is under the plenum or the pump is at fault.

Basically there is a vac line on passenger side of plenum that comes out near the IAC motor and has a connector splice. Separate it & put the Vac pump on the end going under the plenum and put some vacuum into the system under the plenum & see what's up. The other part of the spliced line goes to the vac pump @ the overflow tank, just toward the front next to the horn.
I'm not sure what amount of vac the system is supposed to hold, I can look it up for ya if need be. But fighue it should hold at least 17"hg, I would think.

:thumbsup:
Tom

[cuisinartvette]

TomTOm-Thanks for the tip! :thumbsup:

[Patton]

The systems holds 10-12hgs...

Cuisinart, I am going through the SAME problems right now... We should definetly talk and share knowledge. I have found several write ups and walkthroughs on how to diagnos and repair/replace every aspect of the secondary vacuum system. I found all the hard to find parts as well. I am to the point where I have the knowledge and tools I need for the job, now I am just waiting for my parts to arrive before I pop the plenum off and get dirty.

Here are a couple of great links I have found for our problem.
http://www.corvetteactioncenter.com/forums/showthread.php?t=14272
http://www.pnwzr1.net/PNWZR1.htm

I got my vacuum hand pump at sears (50$) at tested my lines, I have a leak under the plenum and my pump is burned out...
go to here http://www.partszoneonline.com/ for your parts needs, checkout my thread "check engine soon" for all the part numbers, also the part numbers are listed in the CAC link i mentioned before... Let me know how you are doing on it and good luck!

[Scoob]

Also, is it common for the doorlock mechanisms to get sticky? Keyless wasn't opening them. You can hear it, but they don't go. Got inside, flipped the lock switch back and forth a 1/2 dozen times and they freed up. Went to lock it with keyless, same thing. Is this an easy fix or am I buying something?
Keyless? Afaik, keyless entry was not an option in '90.

[cuisinartvette]

Has an Ungo alarm with keyless entry. I really don't want to tear into a door panel if I don't have to (If I tough something delicate it breaks), but if I'm there can they be cleaned and lubed or do I have to replace solenoids?

Afaik? :icon_scra