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Factory wouldn't waste time and money designing one if it wasnt needed. Your engine at times produces low vacuum and depends on the tank for vacuum reserve for lights and wipers and HVAC.
(but seriously epoxy the outside or you can get some of that gas-tank liner stuff and pour it in and swish it around (I'd do the outside where you can see it)
M
Remember that it is a VACUUM tank. The 'pressure' is on the OUTSIDE. You could use some FLEXTAPE over that crack; or you could use some dum-dum sealant used on air conditioning lines (stays flexible and tacky). Epoxy would work (on the outside), if it is strong enough to resist the flexing of the tank. (That's why the crack formed.) Those methods can be used to seal it without removing the tank.
Obviously, brazing it would be the best fix....but probably not worth the trouble.........
Last edited by 7T1vette; Jun 16, 2020 at 12:50 PM.
Hello Dorian,
You are more than capable to fix that crack in the vacuum reservoir! Welding, brazing or soldering would all work but might be overkill. Like mentioned above with the vacuum sucking the part on it should last a while.
One thing I might try is to drill a small hole at both ends of the crack to keep it from expanding/growing and then seal it up. They taught me to do this on my old Cessna to stop growth of any cracks.
I would epoxy a square patch over the hole. First apply the adhesive to the metal around the hole and then lay the fabric (Like Fiberglass) over it and seal it with another coat. When done paint over the area to prevent any more corrosion.
What caused it to crack in that location? That is something to wonder about as that crack should not have developed there without some strange forces on it.
Good luck and practice those fiberglass skills!
Be well my friend!
Last edited by ctmccloskey; Jun 16, 2020 at 01:51 PM.
Those 'stiffener' indentations were meant to reduce the amount of flexing when vacuum is maximum and when going to ZERO (engine off). Unfortunatley, the bottom of those indentations is the weakest area in the part, with the most flexing!! That is the most common cause of leakage, along with rust-thru pinholes [and larger].
Keep the original tank so you know the support brackets and holes will align properly. I had this same problem on my tank with multiple cracks on different sides. Someone before me used some kind of epoxy to fill the cracks but the epoxy failed. I taped over the vacuum nipples and covered the cracks with tape and then removed the paint and exterior rust with a glass bead blaster. I had the cracks tig welded. A good welder will pick the correct rod and welder setting to keep from burning through the metal. The welds are barely visible. I powder coated it black and then used POR 15 inside the tank. I wrapped the tank in stretch wrap to protect the paint while putting it back in and then cut the stretch wrap away before final tightening.
Worst case scenario you'll have to take it out and fix it later. Not now. You got enough things going on with this car right now.
It was yet another case of “while I’m at it” I needed to drop the brake booster, horn relay and power steering lines to be able to locate a remote reservoir for the hydraulic clutch.
That Loctite product looks pretty good. I’m expecting this to work well.
It was yet another case of “while I’m at it” I needed to drop the brake booster, horn relay and power steering lines to be able to locate a remote reservoir for the hydraulic clutch.
That Loctite product looks pretty good. I’m expecting this to work well.
If in that deep, I would change the booster. Just sayin.......
Fixing a vacuum tank
You could use some FLEXTAPE over that crack; or you could use some dum-dum sealant used on air conditioning lines (stays flexible and tacky). Epoxy would work (on the outside), if it is strong enough to resist the flexing of the tank. (That's why the crack formed.) Those methods can be used to seal it without removing the tank.
I needed to drop the brake booster, horn relay and power steering lines to be able to locate a remote reservoir for the hydraulic clutch. 
