Great, snap off
Thread Starter
5th Gear
Joined: Oct 2012
Posts: 5
Likes: 0
From: Mobile Al
Great, snap off
Hey guys and gals,
so on the ongoing project which is my '84 C4, I found that I was getting a lot of water in my fuel. We pulled the rear fuel cover and found the sending unit had rusted just about 3/4 of the way around. I then started to try to get the bolts out. "bink" Well crap, bolt broke the head off. start the soak using everything I had, Deep Kreep, Kriloil, Penetrating oil. I kept applying for 3 days. tried to remove using light rocking, "bink", "bink". Ok S*&ew it, get he Makita Impact and just snap them all off.
So now here we are. Has anyone done anything like this or info on how to get the rusted remnants of bolts out of the tank so I can replace the sending unit.
Thanks in advance
so on the ongoing project which is my '84 C4, I found that I was getting a lot of water in my fuel. We pulled the rear fuel cover and found the sending unit had rusted just about 3/4 of the way around. I then started to try to get the bolts out. "bink" Well crap, bolt broke the head off. start the soak using everything I had, Deep Kreep, Kriloil, Penetrating oil. I kept applying for 3 days. tried to remove using light rocking, "bink", "bink". Ok S*&ew it, get he Makita Impact and just snap them all off.
So now here we are. Has anyone done anything like this or info on how to get the rusted remnants of bolts out of the tank so I can replace the sending unit.
Thanks in advance
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Displace all of the fuel and fuel vapors with something; water, inert gas...whatever you have handy.
I assume they broke off flush with the top of tank? If there is some sticking out, grab 'em w/Vise grips, then heat the nut w/a torch, thread 'em out.
If broken flush or in the hole, I'd drill out the old nuts entirely, weld in new ones.
I assume they broke off flush with the top of tank? If there is some sticking out, grab 'em w/Vise grips, then heat the nut w/a torch, thread 'em out.
If broken flush or in the hole, I'd drill out the old nuts entirely, weld in new ones.
Melting Slicks
Joined: May 2019
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From: Mid-Atlantic
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A lot of folks have said that you can get to the other end of them from inside, but I found that not to be the case on my '90.
Ended up replacing the fuel tank last year. That area was all rusted anyway.
The only other thing would be empty the fuel from the tank and drill em out.
Even with the tank empty, I'd still just use a manual hand drill.
Ended up replacing the fuel tank last year. That area was all rusted anyway.
The only other thing would be empty the fuel from the tank and drill em out.
Even with the tank empty, I'd still just use a manual hand drill.
Melting Slicks
Joined: Feb 2003
Posts: 2,699
Likes: 815
From: Saskatoon Sask.
Melting Slicks
Joined: May 2019
Posts: 3,292
Likes: 1,431
From: Mid-Atlantic
2025 C4 of the Year Finalist - Unmodified
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2021 C4 of the Year - Unmodified Finalist
Tom's way probably is the best way to go about it, absent replacing the tank itself.
For anyone who does decide to replace their tank for whatever reason, I will say that it took me almost two weeks to do it. But it was also my first attempt at doing it, so it was kind of on and off job.
After the first time doing it, I'd say you could probably do it in a day/day and a half with a helper where needed if you start early. Just be sure to have new hardware and straps before jumping on it.
Like most every other pain in the rear end job it's usually much, much smoother going the second time around. Though I don't foresee having to ever do it again in my lifetime.
For anyone who does decide to replace their tank for whatever reason, I will say that it took me almost two weeks to do it. But it was also my first attempt at doing it, so it was kind of on and off job.
After the first time doing it, I'd say you could probably do it in a day/day and a half with a helper where needed if you start early. Just be sure to have new hardware and straps before jumping on it.
Like most every other pain in the rear end job it's usually much, much smoother going the second time around. Though I don't foresee having to ever do it again in my lifetime.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I had not thought about this but it's an excellent point. And you can't heat those nuts. 
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I haven't looked at a C4 tank for years. I may be wrong. The 'threads' may be blind inserts welded to a metal ring that is secured inside the tank, probably with spot welds, possibly with rivets that are under the perimeter of the sender flange. The threaded holes are going to be blind to prevent a leak path for both liquid and vapor by the threads.
Could it be possible to find and drill out the spot welds (rivets) remove the ring and renew the threaded bungs? Or go to nuts, Or something. It would be worth a cleaning of the flange surface to inspect for the attachment method, and conduct a close visual inspection regarding feasibility of implementing this idea. If the interior of the tank is serviceable, this could save a lot of work by not having to do a tank R&R.
Could it be possible to find and drill out the spot welds (rivets) remove the ring and renew the threaded bungs? Or go to nuts, Or something. It would be worth a cleaning of the flange surface to inspect for the attachment method, and conduct a close visual inspection regarding feasibility of implementing this idea. If the interior of the tank is serviceable, this could save a lot of work by not having to do a tank R&R.
The OP having an '84 it's certainly advisable to attempt something other than tank replacement if practical I'd think!
Last edited by WVZR-1; Jan 18, 2022 at 11:11 PM.
Instructor
Joined: Nov 2020
Posts: 135
Likes: 22
From: Detroit Michigan
I haven't looked at a C4 tank for years. I may be wrong. The 'threads' may be blind inserts welded to a metal ring that is secured inside the tank, probably with spot welds, possibly with rivets that are under the perimeter of the sender flange. The threaded holes are going to be blind to prevent a leak path for both liquid and vapor by the threads.
Could it be possible to find and drill out the spot welds (rivets) remove the ring and renew the threaded bungs? Or go to nuts, Or something. It would be worth a cleaning of the flange surface to inspect for the attachment method, and conduct a close visual inspection regarding feasibility of implementing this idea. If the interior of the tank is serviceable, this could save a lot of work by not having to do a tank R&R.
Could it be possible to find and drill out the spot welds (rivets) remove the ring and renew the threaded bungs? Or go to nuts, Or something. It would be worth a cleaning of the flange surface to inspect for the attachment method, and conduct a close visual inspection regarding feasibility of implementing this idea. If the interior of the tank is serviceable, this could save a lot of work by not having to do a tank R&R.