Something is eating my tank screen filter - PeachParts Mercedes-Benz Forum

benedict · #1 10-19-2013, 06:26 PM

It's only been 5 years since it was last done.

I'm glad I didn't leave it too much longer or I might of been taking the screen filter out in little pieces.

I have never dropped anything into my tank in the way of cleaners. All my purges are done straight from the can and directly in the engine bay.
Even my return is redirected into my purge setup.

It is an original Genuine part. The only difference is MB now manufacture the part out of aluminium instead of brass.

We don't run biodiesel here as it's illegal nor is it available.

And anyone who hasn't replaced this before, expect to be coated in diesel. There is no way to describe it. Nitrile gloves will protect your hands but diesel runs past these, down your arms and drips off your elbow onto your chest.

whunter · #2 10-19-2013, 07:11 PM

That looks like the PH is wrong, moisture in fuel forming acid.

.

layback40 · #3 10-19-2013, 07:17 PM

You are getting water in your tank or there has been some in there for a long time.
Condensation?
Moisture sucked in via the breather?
Filled the tank in the rain?
Bad quality diesel?
High humidity?
Washing the car around the filler with a high pressure cleaner.
Do you ever find water in the base of your fuel filter?

Graham · #4 10-19-2013, 07:48 PM

I recall reading a study about corrosion in diesel handling and storage equipment conducted by the Battelle Institute. It was kind of preliminary, but sounded plausible.

Apparently corrosion has occurred mostly since sulphur in diesel was reduced. However, what they found, was that there was acetic acid (same as vinegar) at the bottom of the tanks. And they also found ethanol present. But where would those come from?

Apparently the reduction in sulphur creates a better environment for certain bacteria. The bacteria feed on the ethanol and create acetic acid.

They did not know where the ethanol came from, but guessed it might be from tank trucks that are also used for gasoline that contains ethanol.

Solution is to use a diesel additive that is designed to kill bacteria. I have used a product called Biobor in the past (in my boat diesel tank). It went off the market for a while here in Canada, but it seems to be available again. There are several others that should also work. Very low cost. Just remembering to use it has been my problem!

By the way - how did you know your screen was bad?

vstech · #5 10-19-2013, 08:51 PM

Quote:

Originally Posted by benedict

It's only been 5 years since it was last done.

I'm glad I didn't leave it too much longer or I might of been taking the screen filter out in little pieces.

I have never dropped anything into my tank in the way of cleaners. All my purges are done straight from the can and directly in the engine bay.
Even my return is redirected into my purge setup.

It is an original Genuine part. The only difference is MB now manufacture the part out of aluminium instead of brass.

We don't run biodiesel here as it's illegal nor is it available.

And anyone who hasn't replaced this before, expect to be coated in diesel. There is no way to describe it. Nitrile gloves will protect your hands but diesel runs past these, down your arms and drips off your elbow onto your chest.

sydney... does it ever get cold there? ever use any methanol/water remover in there? I agree with whunter... aluminum does NOT like water.
I'm skeptic about any bacteria claims...

Graham · #6 10-19-2013, 09:42 PM

Quote:

Originally Posted by vstech

... aluminum does NOT like water.
I'm skeptic about any bacteria claims...

?? Boats are made from aluminum. It is fine even with sea water. An oxide layer protects aluminum. (More here)

Aluminum should not corrode submerged in diesel fuel. But presence of water, crevices and lack of oxygen will cause corrosion. Being in contact with the steel tank would also be bad (there should be a rubber gasket).

<>>

Last Fall, I replaced the aluminum diesel tank in my boat after 35 years service! It had corroded within the end seams below the normally full level. Much the same environment as benedict is finding. Now have nice sturdy plastic tank!

Don't discount bacteria being the cause of the pitting - anyone who has owned a diesel boat knows how bacteria can grow in diesel fuel. Key is to keep water out of system so bacteria have less chance of growing. Hard to do in some cases. Using the proper diesel additives will help.

benedict · #7 10-19-2013, 09:48 PM

Quote:

Originally Posted by layback40

You are getting water in your tank or there has been some in there for a long time.
Condensation?
Moisture sucked in via the breather?
Filled the tank in the rain?
Bad quality diesel?
High humidity?
Washing the car around the filler with a high pressure cleaner.
Do you ever find water in the base of your fuel filter?

Hi Layback,
I suppose moisture could get sucked in through the breather but is it avoidable?

Possibly bad quality diesel. I usually fill up from either Shell or BP but I stopped using BP a few months ago because I found black stuff floating around in my diesel. It was similar in texture to lemon bits floating around in a fresh squeezed lemon juice, but black. I kept a jerry can of this bad stuff in the hope of having it tested.
It does get humid here on the coast.
Only use high pressure when cleaning the underbody and I've just fitted a nice new blue coloured seal on my filler cap from Pelicanparts.
Just emptied the contents of my main filter into a glass jar but no sign of water.
Turnover is quite high-a tank of diesel lasts me about 6 days.

benedict · #8 10-19-2013, 09:59 PM

Quote:

Originally Posted by vstech

sydney... does it ever get cold there? ever use any methanol/water remover in there? I agree with whunter... aluminum does NOT like water.
I'm skeptic about any bacteria claims...

It can get coolish in Sydney but nothing compared to what you guys can get. 2 degrees Celsius/35 Fahrenheit.

Graham · #9 10-19-2013, 10:09 PM

Besides using a bio diesel additive, one other suggestion:

When you replace the strainer, you might try giving the flange area where you are seeing pitting a couple of coats of POR-15. POR-15 is used for coating fuel tanks, so it will stand up to diesel or gasoline. It should protect the aluminum parts you can coat from whatever is causing the corrosion. (But not the screen!)

By the way, a search brings up lots of stuff on bacterial corrosion of aluminum. Aircraft tanks have apparently had this problem for years.

Too bad they didn't switch to a polymer strainer.

vstech · #10 10-19-2013, 10:09 PM

2C is cold enough to cause weak diesel's difficulty starting, but only the pretty worn out ones...
what were the symptoms that caused you to pull the TS?
perhaps this is a good place to use the cheaper aftermarket all plastic screens? I doubt we're getting any bronze/brass ones anytime soon...

benedict · #11 10-20-2013, 01:16 AM

Quote:

Originally Posted by Graham

I recall reading a study about corrosion in diesel handling and storage equipment conducted by the Battelle Institute. It was kind of preliminary, but sounded plausible.

Apparently corrosion has occurred mostly since sulphur in diesel was reduced. However, what they found, was that there was acetic acid (same as vinegar) at the bottom of the tanks. And they also found ethanol present. But where would those come from?

Apparently the reduction in sulphur creates a better environment for certain bacteria. The bacteria feed on the ethanol and create acetic acid.

They did not know where the ethanol came from, but guessed it might be from tank trucks that are also used for gasoline that contains ethanol.

Solution is to use a diesel additive that is designed to kill bacteria. I have used a product called Biobor in the past (in my boat diesel tank). It went off the market for a while here in Canada, but it seems to be available again. There are several others that should also work. Very low cost. Just remembering to use it has been my problem!

By the way - how did you know your screen was bad?

Interesting re: contamination. It wouldn't surprise me that the lack of sulphur could eventually damage machinery. I bet those government documents will remain top secret.

I've noticed that the diesel is no where near as oily as it used to be and the smell of it leans more towards that of paint thinners!

I've found a similar product to the one you mentioned as that product isn't exported here- will give it a go.

I wasn't planning on changing the screen filter. The maintenance job was to replace the threaded flex hose coming out from the screen filter as it had begun to weep diesel, but I figured since I had drained the tank already and was covered in diesel, I may as well have a look/see at the tank screen whilst I was there.

Attached is a photo of the original 19 year old hose.

layback40 · #12 10-20-2013, 04:14 AM

Quote:

Originally Posted by benedict

Hi Layback,
I suppose moisture could get sucked in through the breather but is it avoidable?

Possibly bad quality diesel. I usually fill up from either Shell or BP but I stopped using BP a few months ago because I found black stuff floating around in my diesel. It was similar in texture to lemon bits floating around in a fresh squeezed lemon juice, but black. I kept a jerry can of this bad stuff in the hope of having it tested.
It does get humid here on the coast.
Only use high pressure when cleaning the underbody and I've just fitted a nice new blue coloured seal on my filler cap from Pelicanparts.
Just emptied the contents of my main filter into a glass jar but no sign of water.
Turnover is quite high-a tank of diesel lasts me about 6 days.

You had bugs in there!!
I use Caltex only.
Looks to me like you had a bad tank of fuel. It could have caused the problem. Over the years you probably collect a bit of water on the tank. The fuel pick up is not right at the bottom so there is a space for water to collect.

Graham · #13 10-20-2013, 10:27 AM

I see from your picture, that there is a rubber O-ring, but the aluminum still screws into a steel boss. With water present above the boss, even without any bacterial corrosion, the aluminum will corrode first (if galvanic corrosion takes place). Perhaps there should be a barrier between the aluminum and the steel. Maybe Teflon tape on threads and a thin plastic donut or layer of sealant between the screen flange and the boss.

I didn't know plastic screens were available. If so, they might be worthwhile checking out.

barry12345 · #14 10-20-2013, 11:58 AM

Get an older used brass one and clean it up for reuse if only aluminium replacement ones are currently available. A dielectric difference could have helped the issue along as well.

Sbean · #15 10-20-2013, 02:48 PM

Yesterday I cleaned the tank screen on my 1980 300TD because of a fuel starvation symptom. The screen was pretty clogged, but no corrosion. No aluminum: plug is brass.