Vacuum reservoir - want to repair but don't understand it

[jeffahart]

I started looking to fix my shelved Vacuum reservoir. I don't get how the manifold was originally attached to the can. I was thinking I would tin it but that red thing looks like a gasket. The manifold spins in place. I was just wondering how it's attached. I want to fix it without breaking it.

Pic below.
Thanks,
j

[tdangle]

I think I would just epoxy or silicone the center piece to seal it. The larger fitting went to the manifold block behind the carb and the smaller fitting goes in the the vacuum switch under the dash. The can just acts like a large reservoir. Think of a water tower with lots of water coming in and a small amount going out.

[jeffahart]

Originally Posted by tdangle

I think I would just epoxy or silicone the center piece to seal it. The larger fitting went to the manifold block behind the carb and the smaller fitting goes in the the vacuum switch under the dash. The can just acts like a large reservoir. Think of a water tower with lots of water coming in and a small amount going out.

Thanks,
I'm calling the piece for in/out vac attached to the can a manifold. Didn't mean to confuse. How was it originally attached to the can? I think I may need to disassemble the can.

thanks again.

j

[jeffahart]

Here's what the manifold/fitting looks like. The red rim you see before disassembly is not a gasket. It's rubber flapper. Looks like it makes the seal from vacuum and allows bleed off.

Now I need to get some thin rubber so I can fix it.

Pics attached for anyone interested

j


Rubber flapper. Now hardened and petrified.





Canister manifold apart.

[jeffahart]

Just did a little digging online; here's a check valve. Any thoughts?

https://www.ecklerscorvette.com/corv...1968-1982.html


j

[saxart]

At the risk of sounding like an idiot, what is this thing? My truck doesn't have one...

[tdangle]

Interesting the replacement is just a plastic ball with 2 connections no valve or bleader

[jeffahart]

Originally Posted by saxart

At the risk of sounding like an idiot, what is this thing? My truck doesn't have one...

It's for the vents on the AC equipped trucks. And the originals are kind of cool, they look like a fruit can painted black.


j

[RichardJ]

It's a one-way check valve. At wide open throttle, manifold vacuum drops to near zero. Without the canister, the AC mix and defrost doors would return to a default position. The canister acts as a reservoir to keep the doors from moving with varying engine loads. The one-way valve keeps the canisters vacuum pressure from bleeding back to the manifold.

I've read that the plastic balls either have a built in valve or a in-line valve is installed somewhere in the line, depending on application.

[vitamin_c95]

This is on my to do list. The vacuum lines to it are brittle and are breaking off Every time I glance at them. I just need to find the routing...someday. focusing on making it roadworthy first.

[jeffahart]

Originally Posted by tdangle

Interesting the replacement is just a plastic ball with 2 connections no valve or bleader

Yeah, I think you are on your own to get the check valve with the replacement. I had no idea and just assumed an empty can. I put on the plastic replacement ball and a check didn't cross my mind. I'm glad I got nosy and tore it apart. I will tin a patch and put in a brass barbed nipple. Then I will use an inline check valve.

I want the goofy fruit can back in action, been saving it till I had some time. I thought I would just solder it up. But now it's turning into a mini project.

Oh, and the check valve pieces is pot metal. Just for the record.


j

[jeffahart]

Originally Posted by RichardJ

It's a one-way check valve. At wide open throttle, manifold vacuum drops to near zero. Without the canister, the AC mix and defrost doors would return to a default position. The canister acts as a reservoir to keep the doors from moving with varying engine loads. The one-way valve keeps the canisters vacuum pressure from bleeding back to the manifold.

Hey Richard. Do you know if the round ball replacements have an internal check valve? I been using one without. I wonder if my recirculating vent is moving open and closed and I'm not noticing. Need to check that out.

Kind of mute for me since I'm fixing my original. But it was pretty lame of me not to realize the need.

j

[jeffahart]

Did a quick fix on the reservoir. So I figured I would wrap up the thread with my fix. Took a couple hours to fix because I had to solder some of the seams around the lid and bottom as well as the patch. But it's a pretty quick fix up. Here's some info on the fix.

I am going to install with an inline check valve. Right now I;m running the round aftermarket reservoir, it has no check valve. There has been no ill effect. I run my AC and the way it is setup my heater control valve stays shut, it is a vacuum close. I fixed my AC this spring and it blows mid to upper 30s on 100+ days now. My recirculating vent stays open also. I think if my heater valve was opening and closing I'd be suffering in the cooling temp.

But, as soon as I shut the engine off, the vent closes. So that means my heater valve is opening also.

I did a test with the check valve inline with the after market reservoir. The vent holds open when engine is shutoff using the check valve. For how long, not sure. I will keep an eye on it and see.

I used a piece of copper sheet for the patch. I had some stainless too, but decided on copper with brass nipples.

A note on the fix. I broke the seams around the rim, I think when putting pressure on the top when I drilled it out. The bottom of the can had a seam leak too.

I soldered the brass nipples and leaking seams. It holds vacuum.

j