71406

When the car is running, headlights and wiper door work fine (although the wiper door is slow to open), but when the car sits overnight all vacuum is gone. Is this normal?

Reason for asking is I've been tearing my hair out trying to repair some wiper issues. Turned out I installed a junk aftermarket Wiper Arm Vacuum Switch that was leaking vacuum. Wilcox came to the rescue by selling a Made In American version of the switch that corrected the problem. While I was into the system i replaced the wiper vacuum relay and changed the check valve and filter. Im trying to find out if i still have a vacuum problem. I would guess that the system should hold vacuum overnight. So do i still have problem to chase down or is this normal?

Thanks

4-vettes

My quess is that this is normal. I have never been able to get my vacuum system that tight. l'll be watching this thread, if that is possible, I'd like to learn how.

interpon

My 79 has enough vacuum to close or open headlights for about 5 minutes….once..

i have read anywhere from new owners of an 80 last for a month? To if it holds an hour, it is good after 40 years.

post 9 references park vacuum on earlier years?

https://www.corvetteforum.com/forums...-for-a-c3.html

another reference here
https://www.corvetteforum.com/forums...-shutdown.html

67:72

The dozens of slip-on connections and components in the system(s) makes it unbelievable to me that it would keep overnight. I would be pretty impressed if it lasted 30 minutes!

calwldlife

common yes, normal no.

derekderek

lose vacuum overnight. normal for 40 year old vacuum system. take every vacuum hose off. cut them all about 3/8ths inch shorter. a bunch of tiny leaks add up. worst case scenario, start engine before trying to use wipers or headlights...

bobby70

I replaced every hose and vacuum. parts in my 70 and when I shut the car off I can raise the headlight once and wiper door once thats it all the new parts. from China are all JUNK if every. thing works when running your doing good

Jebbysan

I have personally never seen one hold vacuum for longer than about 30 minutes.......
I will not run the shitty filter and most of the repop check valves are garbage......can't even suck through one side. Good pliable hoses with zero aging or cracking are a must. New relay valves are a 50/50 shot......no matter where they come from.
The filter to me is another restriction and c'mon......what exactly are you going to suck into the engine from that port? It would have to make it past the check valve and it would be too small to cause harm.
Check your check valve first.....

Read this:
http://www.corvette-101.com/vacuum.htm

Jebby

L-46man

There is no real check valves, nor accumulator in the system.

In the later models, there are vacuum cans. (accumulator)...HOWEVER the system will leak down in MINUTES, anyway.

All is good! Carry on!

Unkahal

Rescue Rogers

What year is your car. They all had a vacuum tank and a check valve just after the fitter. That T is a check valve. I wouldnt say its very good. I replaced most of my system and got good seals. I have an in iine vacuum gauge and it holds vacuum a long time but if you cycle the system it used most of it up, but again its gone by morning. Unless you trim back every old bit of hose an inch or so it will probably leak. If the system works I wouldnt mess with it unless you are bored and want to trim the hoses so they hold tight and dont come off easy

bluthundr

That is completely normal. The purpose of the vacuum reservoir is so that if you shut the car off before turn off your headlights or shut your wipers off, you can still close them without having to restart the car. It's not realistic to expect it to last for hours.

71406

Thanks to all who replied to my post. Good to know nothing else is wrong and I’m happy everything is now working properly.

As someone mentioned in an earlier post, the biggest problem related to these vacuum systems is the junk replacement parts on the market. You should never assume these aftermarket parts are working properly just because they’re new. In my car, a recently installed wiper arm vacuum switch failed but I assumed it was good because it was new. In an attempt to solve the problem I purchased a new aftermarket check valve that was also defective. Took me a long time to figure this all out.

Thanks again for your help!