My 81 F250 vacuum canister was rusted out and it had one port. I had an parts truck 86 f150 and the can was good but it has two ports. So I cap one and ran the vacuum line on the nip that said vac (center most one). I started truck and watched the can's ends suck in. Is that normal? Never notice before because it was rusted out. I tried switching them and the can does the same thing. Thanks

 

How far does it suck in? A little bit shouldn't be a problem.

 

Sucks in where you can see it move, then I take the cap off the port and you can hear it release and watch it move. Its just the ends

 

If it is only flexing then that's ok. But, if the can is getting crushed then that's not good.

 

With it plug up motor runs low, when unplug motor runs a little higher. All lines look good and the unused lines are plug. I don't run smog pump the belt has been off for years same as the plugged lines. Is that vacuum line supposed to suck the canister like that? Do want to mess anything up by running it like that. I drove truck around it seemed ok

 

You have not told me how much the canister is getting deformed. I've asked but no answer - other than "sucks in where you can see it move". So, I'll say again: If it is only flexing then that's ok. But, if the can is getting crushed then that's not good.

If you want another answer you'll either have to video it and post it here or measure the deflection. I cannot go on "you can see it move".

 

It should not deform. You are mixing '86 with '81 and are probably missing something. Sending from my phone so I can't research. Think about it though. ...if the can regularly deformed it would fail in no time.

 

What is your definition of "deform"? Do you know that he has the same definition? No, you don't. Nor do I. But, all of the canisters deform to some extent. So, until we know how much his is deforming we cannot answer the question.

 

The ends are flexing in I say about 1/4 to 3/8.

 

The 86 had two ports so I use the port the center one it said vac, and vacuum was being suck in the other one so I cap it off. The 81 canister was a closed one line system. I never got the chance to look at the old one it was leaking and rusted and had white caulk around the edges so I did not see any other lines, I guess to keep it from leaking didn't work.

 

And what does the can do? Does the can just help keep vacuum pressure?

 

That's a lot of flex. However, if they bulge out before the vacuum comes on then the flex is only about half that.

My belief is that you'll be ok with that canister. And, the worst that could happen is that it fails. If it does just plug the line so you don't have a leak. But, you'll have no reserve for your HVAC controls so when you gun it the system will go into Defrost. No problem, just replace the canister with another one.

 

When you say reserve how can that be if the line always pulls. Does it change when driving? Sorry just never put no thought into.

 

Yes. The manifold vacuum goes from something like 24" when coasting to almost 0 at full throttle. So, without the reserve you'd loose the HVAC controls at full throttle.

But, there's supposed to be a check valve where your line T's, with one going to the canister and the other into the cab. I hope it is still there.

 

There is a lot running everyway tomorrow I will look closer at everything. Thank you