Why my W124 fuel tank rusted out so quickly

I'm certain this is why

[@TonyLiveTV]

Great catch! Now maybe the fuel situation comes to an end.

[@IDYLBERRY]

Thanks for this valuable information. I hope you can save the fuel tank.

[@OYABUNG_WA]

So glad I have found your channel - the right level of knowledge with the kind of humor I like :) I am located in Perth also. Just imported a W460 230GE and it's just at the engineer before I can take it for an inspection and hopefully get it registered. It does require a few cranks to start up so I am getting them to check the pressure to see if the problem can be isolated. The fuel filter and pump (with the check valve) are pretty inexpensive so I am just getting that changed out anyhow. Hopefully it can be resolved - it doesn't appear to have an issue while running but I am not sure about a warm start that may point to the accumulator...anyhow test test test before just randomly part swapping!

[@MMWA-DAVE]

checking the pressures is a good first step, especially the one where leak down pressure is monitored over a 30 minutes period. It can also be the injectors themselves leaking or the fuel distributor itself. It wouldn’t hurt to send it off to colin at k-jet specialists in QLD for a rebuild if any doubt. (including the warm up regulator if its a K-Jet car non KE) so they can be setup together perfectly.

[@rfbu]

Hi, can you share with us where you get that printout? They look useful

[@grindelwald8651]

Yeah really need that. Pls tell us

[@markmulcahy1958]

You could use N2 or welding argon to blanket the tank. Inert and easily available

[@robgimenez5031]

Well done

[@vornamenachname5589]

Thanks, i guess this is the reason for the Pschhhh-Sound my W126 does when i open the fuel tank.

[@markvincent4628]

Hello there I recently found your channel and was very impressed with the thoroughness of your presentation. My question is where can I find that manual you have in this video. I own a 1993 300d and do the majority of my own wrenching and have always wanted to get my hands on a usable shop manual. There very few and far between.

[@tony66au]

Well THATS a Relief................... (Sorry, Dad joke :-)

[@shaazy]

The science behind it is so fascinating! My 1991 300e's fuel tank was repaired, no idea on the quality of the job, but I keep getting fuel vapors in the cabin everyday (temperatures are around 30 degrees Celcius where I live but aside from that, car starts, idles, and drives normal). I went investigating in the back and first suspected the fuel sender. Changed the gasket there. No change. Then I landed on this fuel vent valve, changed this. Still getting vapors. Interestingly, the vapors are coming out distinctly from the gas cap (also new MB original), can smell them when I open fuel door and put my nose in. There's no 'swoosh' when opening the cap either. Your vid does confirm my suspicions, that tank pressure is rising and releasing through the cap. Question is, can a faulty fuel tank cause this? Cause that's what the mechanic suggests. Or is the vent system clogged somewhere down the line leading to abnormal tank pressures, which then HAVE to be released through the cap. Thoughts?

[@HTMLEXP]

That might explain why my 190E, on a hot day, sometimes gives off a sound like a ship's horn. Valve 51 has probably failed in the closed position or there's some blockage in the evaporative emissions capture so that the fuel cap has to release the pressure.

[@MMWA-DAVE]

well that’s concerning. If there is a blockage you may end up with a caved in tank when it cools down.

[@HTMLEXP]

@@MMWA-DAVE it's a worry, I try to keep it mostly full, but the tank always seems pressurised to a degree - the cap almost jumps into my hand when I remove it. It's due in at the independent Mercedes specialist for replacement of the rear main seal, clutch and springs. I'll ask him to investigate then.

[@XPbIM3]

I've also heart some fuel tanks were collapsing due to valve failure and vacuum build up.

[@MMWA-DAVE]

yep, this valve is what prevents vacuum build up. Obviously you must also not have any blockages in the line after it to the charcoal canister or the canister itself

[@noldus89]

​@@MMWA-DAVEis there any specified interval for the charcoal canister itself to be changed ?

[@brittanywright9646]

So when the tank was removed with all that grime, this failed valve was the cause of it?? Hearing the pressure in the tank once the cap is removed is an indicator that the valve is still functioning, however, when the outside temp is low then there isn't that "woosh" noise of pressure release so how do you check/test this? I can see that little valve failure could potentially take out the fuel pumps, injectors, tank, etc. I wonder if a secondary one added on a Y splitter or even tandem further down would change the operating pressures or if could be used in the event of the first one failing.

[@MMWA-DAVE]

i dont know about the dirt in the tank that probably still was an external issue like a dirty fuel station. The valve not working in my opinion is what allowed the tank to rust so quickly. Later cars dont even have this valve, presumably its integrated into the tank, late w140’s for example this is mentioned in the service manual. My 210 also doesn’t have this valve but its not documented anywhere if its in the tank or in the charcoal canister. ideally there should be slight pressure when removing the cap when the car is warm. There wont be anything when its cold.

[@dikranberg7600]

❤❤❤❤❤😊😊😊

[@christopher6161]

how did you determine the valve failed

[@MMWA-DAVE]

there is literally no restriction to airflow in either direction, the internals have failed. Suction on tank side should have near no restriction, pressure from tank side should offer a bit of resistance

[@CompaJake]

How do you get directly under the fuel tank ? By taking it out ? Or how

[@MMWA-DAVE]

@@CompaJake the connections are under the car which must be disconnected first before removing the tank.

[@nehuge]

Can I switch this out preventatively without spilling fuel?

[@MMWA-DAVE]

no fuel shoul come out of here unless the tank has been filled right to the top of the filler neck

[@rondafasano8226]

😭 promo sm