Leaky Clear Overflow Tank Lid - 1970 GS

Discussion in 'Wrenchin' Secrets' started by Brett Slater, Oct 9, 2017.

  1. Brett Slater

    Brett Slater Super Moderator Staff Member

    I've noticed the last few times out there's been some coolant on the upper part part of the inner fender. Deductive reasoning has led me to believe this is caused by the lid I currently have not fitting snugly to the tank body and seeping/leaking out while driving, going over bumps & hills, etc..
  2. BYoung

    BYoung Stage me

    Is your current top missing the thin rubber gasket that is supposed to be there? That could be the issue.
  3. Brett Slater

    Brett Slater Super Moderator Staff Member

    Most likely, yes.

    The car is about 5 minutes from my house so I can't check to be 100% sure but that's probably the issue.
  4. BadBrad

    BadBrad Got 4-speed?

    I've found that over-tightening the tank to the fender can cause the tank to misshapen, ever so slightly, and then the lid doesn't really fit so well. Then you get yourself a leak - at least one cause of same.
  5. Brett Slater

    Brett Slater Super Moderator Staff Member

    Duly noted.
  6. Richie

    Richie Well-Known Member

    On mine I took the gasket off because it was so bad and put a bead of clear silicone in the groove (where the gasket was) and then put it back on the tank. It solved all my leaking problems.
    Dwayne B and Brett Slater like this.
  7. Brett Slater

    Brett Slater Super Moderator Staff Member

    Are you able to take the cover off if you need to?
  8. gstewart

    gstewart Well-Known Member

    I had to do the same thing with a repop unit that I purchased from a member several years ago. I also had to trim a couple sharp edges from the casting.
    Brett Slater likes this.
  9. Richie

    Richie Well-Known Member

    I have never had to remove it but I don't see why you couldn't. It may take a little more work. I knew I would never find the right gasket and silicone certainly is not permanent.
    Brett Slater likes this.
  10. TorqueMonster1

    TorqueMonster1 Making My GS Great Again!

    Make sure you use 100% silicone. Get a tube of it that can be used in a caulk gun. Cut the tip so that you can make a bead that will seal it. A bead too small may not seal it, too big will make a mess. You can practice making a bead on a sheet of paper before you put it on the lid. Make sure it's just good ole plain 100% CLEAR Silicone. Using a tube in a caulk gun should be easier to work with than using one of the smaller tubes you squeeze like toothpaste. Let it fully dry/cure before you start the engine. You won't be able to seal the tube so it can be saved to use in the future, at least not for long. It should come apart fairly easily in the future if you need it to. Didn't mean to get into such detail but some people have little to no experience with silicone, unfortunately I have more than I care to remember. Hope this helps.
    Last edited: Oct 10, 2017
    Brett Slater likes this.
  11. Brett Slater

    Brett Slater Super Moderator Staff Member

    Looks like I'm going to have to try this process in the very near future.

    Last few times out, I've (again) noticed coolant on the inner fender. I attributed it to the upper overflow hose (possibly) being too short. That was until I gently pried at the part of the lid closest to the firewall and it seems to have come a bit detached from the tank body.

    This is one of buicfrank's repro that snapped on very snugly last year when I purchased it. I also noticed the lid had a bit of a bow in it when I had it off today.

    Either way, I don't recall using any silicone last year because the fitment was so good. That said, any particular type recommended? Wiping down my inner fender every time out is becoming a real pain.

    Thanks in advance!

Share This Page