Had a jack slip off a rear, central jacking point and onto the (plastic) fuel tank (Saab). Tank is not ruptured but is caved in somewhat. How would you pop this back out? Can I use compressed air? I'd rather not drop the whole thing if I can help it, but it looks like I could do this, then maybe pop it out with a board or something via the hole for the top-mounted fuel pump. A used tank is tough because the yards puncture them to drain fuel.
Thanks for your sage advice.
Don't use compressed air. You'll also be compressing and heating fuel vapor. Bad idea.
drop the tank (sorry)
How badly is it caved in? Plastic tends to fail the more it is "worked" so if it's not leaking, I'd leave it for now and start looking for a replacement. If you try to pop it back, the chances of it leaking are fairly high.
What are the consequences of doing nothing?
My guess is that it is still holding fuel, just in a slightly different shape. Is it leaking or at risk of leaking?
Go fill up the tank and head down a bumpy road. At 6.04lbs per gallon slamming the bottom should push it out even better if its hot where you are.
Congratulations. Its the perfect time to switch over to a lightweight fuel cell!
As long as you didn't damage the fuel module, I'd not worry about it.
Is the area near the dent smooth enough for a suction cup? HF sells cheepie versions of the lever action suction cups that glass workers use. Or, as someone else already said, if its working normally just leave it alone.
a pound or few of air pressure max should pop it back, don't get nutso w/ the pressure, remember it's lbs/ sq. inch of surface area, don't wanna damage pump or lines
I agree with the "leave it be" crowd. you probably lost a gallon of capacity, tops. Saabs have huge tanks anyway, so I doubt you are going to miss it.
Consider it a fuel savings device
Thanks for the responses. I think I'll let it be for now, and see if some fuel (and warmer weather) don't pop it out.
Just run it, who cares!
Can you get under there with a propane torch and just soften up the dent? What could go wrong?
Actually, just cut out the piece with a pilot arc plasma cutter and stick weld in a new section.
Have you ever seen a tire seated on a rim by spraying in starting fluid and lighting a match???
Wait until the tank is almost empty, it will have lots of vapor. Toss in a match and that dent will no longer be bothering you...
Taiden wrote:Actually, just cut out the piece with a pilot arc plasma cutter and stick weld in a new section.
hard to do with plastic
I don't know how the fuel gauge works in your car, but when I dented the gas tank on my old Monte Carlo the gas gauge would never read below half a tank. I thought I was getting amazing mileage until I ran out of gas.
mad_machine wrote:Taiden wrote:Actually, just cut out the piece with a pilot arc plasma cutter and stick weld in a new section.
hard to do with plastic
Shall I respectfully remind you which forum you are on? 
I would pay money to see somebody stick weld plastic.. and I am not talking melting plastic sticks to weld
I bet if you made some weird material out of iron filings and plastic you could figure out how to make it work. Would probably cost millions to develop though.
My e30's fuel tank has a nice big dent in it not far from the rear jacking point. Either someone went over a curb, or someone didn't put the lift arms in the right spot, lol...
Taiden wrote:I bet if you made some weird material out of iron filings and plastic you could figure out how to make it work. Would probably cost millions to develop though.
I vaguely recall 3m or some such company offering conductive polymers with stranded steel added to them. Not sure how you would adapt it to welding, but I'm also not willing to say it can't be done.
Hot glue something into the middle of the dent that you can get a grip on to pull it out. Razor knife your "handle" off when done, metal L bracket to clamp vice grips onto works well.
Although I agree that it may be best to leave it alone as it could fatigue and create a leak pulling it out.
