Fuel Tank

[gazb159]

Hello Again,
I was recently quoted £750 for a new fuel tank for my E320 estate.
Would this be correct,it seems a bit steep to me.
I have a 1" split in my fuel tank,just to the left hand side of my main fuel pipe to the engine,does anyone think this could be welded,or braised??
Thankyou for your help.
Gary.

 

[balge]

I've had a petrol tank welded before - you need a good welder. Can't remember off-hand, I believe he said something about running car exhaust gas through it to stop it exploding?
I doubt braising it will help, it will taste vile...

 

[hotrodder]

As said it should be repairable. Brazing, even soldering, can be acceptable methods however i'd favour welding these days due to the more corrosive nature of modern fuels... probably not a big deal with the current ethanol levels in petrol however as ethanol doesn't play happily with many materials avoiding dissimilar joints (steel to brass with brazing etc) is a good idea IMO

There's various ways to safely inert fuel tanks for hot work as there are two sides of the fire triangle to play with (fuel and/or O2). Purging the tank with exhaust gases is a bit of an old wives tale... i've heard all sorts of BS about it neutralising fuel residue and personally know several people who used to swear by it until a tank 'popped' on them after believing running a car exhaust through the tank for 20 mins was good enough. Granted modern cars with cataylitic converters cut CO emissions a LOT but part of the reason they soiled their underwear/were lucky to not be seriously injured and ended up with a fuel tank that changed shape and no longer fitted back into the car after it went bang is because CO has an LEL (lower explosive limit) of 12% and an UEL (upper explosive limit) of 75%. Petrol has an LEL of around 1 - 1.5% and a UEL of ~7.5%, diesel is similar but has a much higher flash point

CO is slightly less dense than air so not very good at displacing it from an enclosed space. You get mixing instead, especially at high flow rates. Argon or argon/CO2 (used for TIG and MIG welding respectively) are both heavier than air and so providing the purge is set up correctly (lowish flow rates, purge entry at a low point/exit at a high point) will displace air and reduce the O2 levels to a few parts per million i.e. much, much lower than needed for combustion

Some automotive radiator specialists repair fuel tanks, virtually all of them are gonna have the neccesary kit for cleaning out the tank and leak testing it after repair as it's fairly similar to repairing/recoring radiators

Unless this is a known issue with this model (like the filler pipe rotting on estate versions of the w124) it'd be worth ringing around a few breakers to see if anyone has a used tank for sensible money.

 

[W4E300]

I had a visible leak in the tank of an old BMW 2000 Touring I had and I used this stuff - http://www.permatex.com/products-2/...-systems/permatex-fuel-tank-repair-kit-detail

Got through an MOT and held for the following year I had it. Took about an hour.

Sent from my iPad using MBClub UK

 

[nb_racing]

As said it should be repairable. Brazing, even soldering, can be acceptable methods however i'd favour welding these days due to the more corrosive nature of modern fuels... probably not a big deal with the current ethanol levels in petrol however as ethanol doesn't play happily with many materials avoiding dissimilar joints (steel to brass with brazing etc) is a good idea IMO

There's various ways to safely inert fuel tanks for hot work as there are two sides of the fire triangle to play with (fuel and/or O2). Purging the tank with exhaust gases is a bit of an old wives tale... i've heard all sorts of BS about it neutralising fuel residue and personally know several people who used to swear by it until a tank 'popped' on them after believing running a car exhaust through the tank for 20 mins was good enough. Granted modern cars with cataylitic converters cut CO emissions a LOT but part of the reason they soiled their underwear/were lucky to not be seriously injured and ended up with a fuel tank that changed shape and no longer fitted back into the car after it went bang is because CO has an LEL (lower explosive limit) of 12% and an UEL (upper explosive limit) of 75%. Petrol has an LEL of around 1 - 1.5% and a UEL of ~7.5%, diesel is similar but has a much higher flash point

CO is slightly less dense than air so not very good at displacing it from an enclosed space. You get mixing instead, especially at high flow rates. Argon or argon/CO2 (used for TIG and MIG welding respectively) are both heavier than air and so providing the purge is set up correctly (lowish flow rates, purge entry at a low point/exit at a high point) will displace air and reduce the O2 levels to a few parts per million i.e. much, much lower than needed for combustion

Some automotive radiator specialists repair fuel tanks, virtually all of them are gonna have the neccesary kit for cleaning out the tank and leak testing it after repair as it's fairly similar to repairing/recoring radiators

Unless this is a known issue with this model (like the filler pipe rotting on estate versions of the w124) it'd be worth ringing around a few breakers to see if anyone has a used tank for sensible money.

Interesting.