****Updated info*****

Just got back fromy mechanic...discussing the proposed rebuild this winter.

He said he spoke with old time Corvette mechanic who has seen this problem 1 time in 40 years (this being the second time. Their is a relay between the headlight switch and the actuators that is intermittently sticky. When it gets stuck the can gets crumpled.

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My headlights had issues and were operating on original parts from factory.

I had the mechanic at my friend's gas station install a replacement can and new hoses.

headlights went up and down until I left the lot then the replacement can crushed like a beer can.

That was last year.

I bought another vacuum can and new actuators and took it to a real Corvette mechanic who installed them, cleaned up the right headlight mechanism and put a brand new left mechanism in the car.

lights went up and down great when I picked it up today. Went for a drive....then sun went down and I pulled light switch out....headlights stayed down!

popped hood and saw the brand new damn can was crushed again.

I noticed a hose popped loose from the vacuum can when it crushed (pulled away from the hose.)

I hooked the hose back up, pulled the headlight **** out, and the headlights went up together. Pushed **** back in and right headlight went down and left headlight went down 1 second later.

Obviously the crushed can is affecting the lights retracting together.

Of note....original vacuum can was a thick tin coffee style can. Replacements are thin walled aluminum coffee style cans.

My question is...anybody know why my can keeps getting crushed? Everything from the horses to the actuators to the mechanisms are new or cleaned up to new condition.

Anyone else experience this or similar problem?

 

vacuum is vacuum. actually reduced air pressure. your car can't make any more than anybody else's car. there is no pressure regulator to reduce the vacuum going to the headlight system. they crushed like beer cans cuz they ARE beer cans.

 

This is your problem-






AKA "Chinese Junk"

I went with and upgraded-faster-reliable-21 century design that uses electricity.

If interested -shoot me an email richard454 at comcast dot net and I'll send you a PDF on how to do it!!!

Thread- https://www.corvetteforum.com/forums...c-new-way.html

 

strange ...people usually don't complain about c3s making too much vacuum.

 

Not knowing where you bought it from. That can be part of the problem due to many Corvette suppliers get parts from other sources.

I know the 3 new ones I have that I bought long time ago are steel...and are not for sale. I will use them when needed on jobs I work on at my shop.

So..unless you plan on doing a conversion like Richard has offered. Or you can not get a straight answer from a Corvette supplier on what their vacuum storage cans are made out of.

I have made them out of schedule 40 PVC pipe and put fittings in them and stop the problem.

DUB

 

Does it say.."MADE IN CHINA" on the bottom? its gotta be paper thin for engine vacuum to collapse it in minutes

 

WOW! I have never heard of that happening before. How much vacuum does your motor make? Is the "CAN" made out of Chinese rice paper? Like mentioned, "too much vacuum" is usually not an issue that owners complain about with a C3. Good luck and maybe have custom CAN made if issue continues.

 

I am willing to bet that you have a cheaply made china can ,but I would like to know just how much vacuume your car is making.

 

Repop junk. Look for an original.

 

I've seen aux vacuum cans by Comp and Mr Gasket. Check out Speedway or Summit. Maybe one of those would work. I think you could tee the vacuum line to the relays and ditch the can. Run the engine when you want to open the lights.

 

One big reply for everyone. I purchased the new cans from the regular suppliers (one from Corvette Central and the other from Corverte America.)

8 am going to call Bairs tomorrow....wish I had kept the original can as now it appears it may have been fine and it was the actuators and hoses not the can.

I have no idea how much vacuum I am making.

The aftermarket cans are thicker than a soda can guys....the originals were definitely thicker....just like coffee cans back then....this one is thinner walled and most likely aluminum like today's big coffee cans

 

The vacuum can is just a reservoir to allow you to open and close your headlights a few time without the engine running of course that depends on how tight your system is. It's not needed and could be eliminated. If it is eliminated it may effect the open and close times though.
I like the PVC idea suggested by DUB!

 

I like the PVC idea, too. I thought the can in my 80 was some coffee can Bubba fix at first. I'll be sure to keep it, though.

Even if you had a vacuum pump that could get every air molecule out of your can, the pressure difference is only 1 ATM (~30"). Stock vacuum can be 2/3 of that. I can't imagine that the engineering margin is that narrow by design. Junk replacement parts are at fault.

 

Do you have a standard transmission you downshift when stopping? The system maintenance or plumbing won't affect this. It's simply your engine vacuum doing it. It's probably happening on the first coasting you do when the engine is making the most vacuum. So, you just need a stronger tank.

If you don't want to find an original C3 tank, then you could go to Ebay and look at aluminum surge tanks or vacuum reservoir tanks there. There are also some coolant overflow tanks that could be suitable for this. Lots of them are <$50.

After messing with the headlight system, I found the vacuum reservoir basically held enough vacuum for 1 open or close cycle. I found the lights only worked fast and equally if the engine was left to idle between operations long enough to build full vacuum in the reservoir. Only starting at full vacuum would they would snap open and closed. So, my guess is that the tank is there just so the lights would quickly and equally open or close. Losing the reservoir isn't the end of the world, it just means the lights will operate slowly and unequally.

 

The can on my 81 was disconnected when I got it and a second vacuum line run from a tee up near the engine. Made no obvious difference to how things worked other than I could raise or lower the headlights after switching the engine off.

Thing that I never understood was the can wasn't leaking, everything else was.

 

Hi ernie,
Can you post a pic of one of these crushed cans please? Even for Chinese junk, it seems incredible that they would do this. Under ideal circumstances your car will only produce 18-21 inches of vacuum.
Greg

 

I think this is your car's way of telling you that you need a bigger cam.

 

Hahaha; I love this thread, guys!

1. Just the idea that vacuum could implode one of these cans is great
2. Richard's "Chinese Junk" photo/post - priceless!
3. Fredtoo's post above

Why are people on CF so much nicer and funnier than most of the other Perf Internet Forums?

Adam

 

Because we are bad-***

 

A stock (base engine) 350 engine will pull about 21"Hg maximum. The more wear in the engine, the less vacuum it will make.

21" Hg is equivalent to about 10 psi. So, at max vacuum (ie, coasting down a steep hill at speed), there would be 10 pounds of force on every square inch of that coffee can. With a simple estimate, that would be several hundred pounds of force distributed over that whole can!

The late 70's 'coffee can' reservoir was made of STEEL with decent thickness. Why? Well, coffee was put into that can and the air was vacuumed out! Maybe not to 10 psi level, but it still had to withstand compression forces from atmospheric pressure.

Today's coffee cans?? Or, should I say, Chinese replicas of US coffee cans? Not so much. Junk is junk. If these repo cans can't withstand normal engine vacuum, THEY ARE JUNK!!!!

Ask for your money back...