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  #1  
Old 05-05-2003, 11:16 PM
Claire
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Collapsed gas tank

2 years ago, I purchased a 1984 300D Mercedes. It really had been driven once a week by a little old lady. Was running fine, and got better the more I drove it. I would go to about 700 km, and then fill up. About one year later, on a long trip, the car odometer read 443 km, and the car stopped running. CAA came and "towed" it to a service station where we put gas (yes, I've always put diesel in it) in the car, and it started up, no problem. Since then, it runs out of gas at about 440 kms. Also, when I look in the trunk, I can see that there's a large indentation in the gasoline tank. Why did it suddenly collapse, and is there a way in which I can have it repaired?

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  #2  
Old 05-05-2003, 11:51 PM
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Join Date: Jul 2001
Location: Woolwich, Maine
Posts: 3,598
Claire,

You most likely have a problem with the vent system. When it gets old, and especially if you tend to overfill the tank, the Diesel foam that moves through the vent lines can soften the rubber fittings (small strips of rubber hose that connect the harder vent tubing to a small separator tank in the trunk, and then to another hard line that goes to a vent fitting behind the bumper covering that wraps around the passenger rear corner of the car). As you use fuel, air is drawn in through this system, and if the rubber tube connectors are soft and gooey they will get glued shut. As you use fuel you will create a vacuum in the tank. This more of a problem on long trips after just having filled up. The little venting vessel is behind the passsenger side plastic sheet covering the inside of the fender in the trunk.

This happened to my father-in-law and he noted the gas guage did some odd things, like have the reserve light come on when he had half a tank full of fuel, the engine shut off like he was out of fuel, and the fuel filler cap was hard to get off. When he got the cap off he heard a whooosh of air. Given that these cars have a vented tank, there should not be a major whooosh sound when the cap comes off.

The solution is to have the rubber parts of these lines replaced. It cost my father-in-law under $40 for the job at the dealership.

Good luck and I hope this helps. Jim
__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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  #3  
Old 05-06-2003, 12:10 AM
Claire
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Thanks so much for the quick response Jim. I'll give that a try. I know what you mean about the gas indicators. Since the time I ran out of gas, the fuel gauge shows 1/2 full/empty all the time. Claire
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  #4  
Old 05-06-2003, 02:59 AM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,841
You're saying that the little pump on the side of the IP can collapse the fuel tank? I should have paid more attention in physics class

Sixto
91 300SE
87 300SDL
83 300SD
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  #5  
Old 05-06-2003, 05:51 AM
engatwork's Avatar
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Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 13,648
It does not take alot of vacuum to collapse a tank.
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Jim
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  #6  
Old 05-06-2003, 07:17 AM
Moderator
 
Join Date: Jul 2001
Location: Woolwich, Maine
Posts: 3,598
sixto,

The more square inches of surface area the lower the differential pressure needed, and gas tanks are not built for pressure containment. They have odd shapes that make them more susceptible than, say, a sphere. Gas tanks end up with lots of surface area, poor shaping and a membrane like structure.
Jim
__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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  #7  
Old 05-06-2003, 08:55 PM
Claire
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Posts: n/a
Question

Jim

When I get this done, will the gas tank re-inflate ie, there won't be a dent in it anymore, and that I'll once again be able to put twice as much gas in it? I'm getting tired of stopping every 350 km to re-fuel.
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  #8  
Old 05-06-2003, 09:04 PM
Registered User
 
Join Date: Jan 2000
Location: PA
Posts: 5,440
Claire,

Its a FUEL tank, not a gas tank! And you ran out of FUEL, not gas!

Before you repair the FUEL tank vent, pressurize the fuel tank to push out the dent. It will not pop out by itself if it hasn't by now.

P E H
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  #9  
Old 05-06-2003, 11:01 PM
Moderator
 
Join Date: Jul 2001
Location: Woolwich, Maine
Posts: 3,598
Claire,

PEH is correct. The tank changed shape permanently. It will not return to its original, or some intermediate shape without some force applied to bend the metal back. It is feasible that the tank, which starts life in a pretty structurally unstable state, is still unstable and can be convinced to return to something near its original state with a little extra air pressure on the inside. I would be a little nervous about putting much pressure in there for fear of blowing some fuel line connections off and getting Diesel fuel all over the place.

If the tank is stuck in its new shape, you might take the car to a shop to have it reworked by someone with some additional tools. Seems to me a paintless dent removal tool or something similar should work. Good luck, Jim
__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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  #10  
Old 05-06-2003, 11:15 PM
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Join Date: Sep 2001
Location: central Texas
Posts: 17,281
Having played with all sorts of dangerous things for 33 years without losing any appendages... this deal sends up red flags to me...
I would take all the fuel out of it before I pressurized it... and I would try the suction cups first...
If that did not work I would take out any plugs or the filter that might be at 90 degress to the bend... and try hitting it from the inside to ( hopefully ) 'pop' it back into shape...

Putting pressure on it sounds like a good way to split a seam...and when any pressure was applied I would be standing a long way off and behind something....just call me an ( intact ) fraidy cat....

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