Tag Archives: tank

How to replace the gas tank on a 1968 C3

I recently had a bit of an issue with some pinholes in my gas tank seeping gas which at first glance didn’t look to bad. But as the tank had been repaired before and my repairs didn’t hold it was time for a new tank. Thought I’d write up the process just in case anyone needs it in the future. It’s up to you whether you jack up and support the rear of the car as the tank can be removed without it. But it will give you a lot more room to work in which you’ll be thankful for later.

 

Try to drive your car to as empty as possible before starting to drain the tank. You can remove it without draining it but damn it will be heavy as you lift it out. You can partially drain it by removing the hose from the sender unit in the base of the tank, but this will still leave 5 – 10L of gas in there.

Best way is to siphon the gas out from running a pipe in through the filler cap as that managed to get most of it out for me.

Once the gas is out you need to remove the fuel hoses where they attach to the tank. Remove the large hose at the sender unit, and on the 68 the return hose is on top of the tank so it’s easier to disconnect the return hose at the hard line on the right hand side rail. On mine the return hose was perished inbetween the two so I didn’t have to remove anything unfortunately.

If you have a later model chances are you’ll have a charcoal vapour canister on the left you’ll need to remove at this point too.

Next I removed the sender unit and fuel outlet from the base of the tank. Although not necessary, it’ll save you from accidentally knocking it around while removing the tank later. It apparently takes a special tool, but I just used a screwdriver and hammer to gently tap/rotate the 3 lugs around until the keeper ring popped out. At this point I found the pickup tube was missing the filter sock which explained some crud in the carb when I bought the car. Unit was nice and clean though.
 
I also removed the rubber splash shield around the filler neck and removed the filler from the tank as well to make for easier manoeuvring later.

If you have mufflers out the back then they will be completely in the way if you try to drop the tank. Easiest thing to do I found was to loosen off the clamps where the pipes are usually joined just in from of where they pass though the crossmember in the middle of the car. Once loosened you can undo the hangers and “gently” rotate the pipes down and towards the outside of the car giving enough clearance later to drop the tank. Remove the spare tyre carrier and especially it’s top shield at this point as well to give you room later.

Once this is done the tank straps need to be loosened off. The bolts for these are on the rear crossmember and need to come completely out so the straps are free. Of course on my tank I found only one of the straps was even bolted down! Looks like they didn’t attach one so it didn’t put pressure on their dodgy tank repair. Once the straps are loose it is handy to try to slide the tank back and to the side so that it is supported by the rear crossmember and side frame rail as it will make removing the support easier.

The support bar runs under the front of the tank to support it. This is held on by 2 bolts/nuts on each side (or only 1 each side on my car). To get this off you need to slide a spanner (1/2” I think) in though the handy gaps in the frame rail to hold the bolt head so you can turn the nut underneath. Loosen off both sides and the support will just be held by the back of the tank straps. Once the support is loose you can rotate it around so you can get the straps out of the slots on the back of it. Once the straps are loose slide them off the side of the tank and remove them as it will be easier when dropping the tank.

Now you can push the tank towards the back of the car to enable you to rotate the front of it down to drop the thing out.

Once I got the tank off I found it had 4 previous repairs along the ridge where it sat on the support bar. Research shows this is common as the spots get a lot of flexing pressure from the support. Also looking inside the tank there was a lot of rust residue along this line as well as the tank being is a dodgy state overall.



Reassembly is the exact reverse of the above process but a few tips will make it easier. At the end you’ll end up with a nice shiny tank in there.

1. New tanks are usually just bare steel. You can either paint it, or do as I did and just spray it with a few coats of clear to give it a bit better protection from the elements.

2. The front support bar and rear crossmember should have an anti/squeak pad across the top of them. I threw away the 40 year old stuff that was barely there and just got some rolls of sticky backed felt from the surface protection aisle at the hardware store. The adhesive makes it simple to stick it to the supports and prevent it moving when you are messing round putting the tank back in. I also used it on the underside of the top of the tank straps to protect the top of the tank slightly. Just make sure you don’t use too thick a felt as it will make the straps a pain to try to do up later (ask me how I know).

3. The bolt on my tank strap was 1 ¾” long. I replaced both sides with 2” bolts which made starting the tightening of the straps a lot easier.

4. While the tank is out take a look at the drains from the rear deck. Like mine they may be jammed up with 40 years of dirt. For a quick fix I just poked around with a screwdriver to clear them a bit and blasted from the top with compressed air to flush it all out.

5. While the tank it out it could pay to take a look at the rails and give them a bit of a cleanup and rust protection treatment while you are at it.

6. Before tightening down the tank straps check to make sure that the filler is lined up on top with the opening in the deck.

7. Don’t put the old gas back into the new tank. Chances are if the tank was rusty there will be rust particles in the gas that you don’t want in your new tank. This is not so much of a problem if you have lined the new tank with a sealer like the POR15 gas tank kit.

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