Gas Tank Cleaning

[UPSTATE NY]

Hello, I have a 76 450SL, I haven't had it running in almost seven years. Last year I added gas to the tank and the guage didn't move (it was found to be stuck). The fuel pump failed. I removed the sending unit and found that the old gas had turn into a paste like substance covering the inside of the tank. No rust, but defintiely a foreign substance was now present.

Has anyone had any experience with a dirty tank and how it was repaired ?

A new tank is prohibitive ($1400.00).

I would like to find a way to clean the tank without removing it.

I've been told by a very good source to add a gallon of carburetor cleaner into the tank with some gas and let it set for two week then rinse the tank out with clean gas. The same person said that lacquer thinner would be bad for the inside of tank.

I've got a new fuel pump, filter, etc as well as new injectors, I'd hate to ruin them with tainted gas.

Any info would be appreciated.

Thank You
JOB

[300SDog]

What part of upstate New York...... if you're anywhere near Avon, visit or call the Moto Guzzi shop up there!

On a smaller scale the same problem is chronic with Vintage Guzzi motorcycles. Avon Guzzi MC shop will know toxic waste, chem products that will clean and coat insides of your tank. Hell, they might even know somebody willing to do the job...... figure about $300 for what's involved, was $125 for 4.5 gallon m/c tank on my bike.

Basically, gotta get something like beaucoup Naval Jelly, couple of gallons, to be sloshed around and then rinsed out...... repeatedly, over and over again. And then finally adding some kinda coating for insides of the tank.

Naturally, the first thing you've gotta do is pull the tank from the car.

It's gonna be nasty job, shakin and kickin the tank around - adding, dumping and rinsing chemicals that burn eye-balls out of their sockets, scorch/dissolving flesh from your hands and arms.

The rust dissolving chems themselves aint cheap and are hard to find, probably the worst toxic chemical junk anybody ever dealt with.

That's the permanent solution, dunno what you can do leaving the tank in the car.

[PC Dave]

Ask your mechanic for a local source, someone will specialize in this. Last week I took my '81 SD for a 15k service to my mechanic in LA, the well regarded (on this board) Enrique at MR MB Motors. After some fuel filter clogging on the drive down, we decided to clean the tank as a preventative measure. Looking at my bill, he charged $140 (2.3 hours) labor to remove and reinstall the tank, and the shop that cleaned it charged an additional $120.

[Todd Miller]

Here's the method I use on heavily rusted and even pin-holed fuel tanks.

Drain and Remove tank.
Pressure wash the inside.
Pour in a quart of muratic acid (sold at any hardware store) and very slowly "slosh" around in the tank......This is some super methyl-ethyl-bad-***** so be sure to where goggles, gloves and a real respirator.

As the muratic acid works, it will eat all the rust out AND it will be smoking in the process! Give it 10 minutes or so to cook and then start filling the tank with water.

Pour all of this out......good for weed abatement and fence post protection, etc.

Now rinse thoroughly with water and blow dry with compressed air.

Pour in a quart of denatured alcohol to absorb any left over water.

Pour out the alcohol and dry with compressed air.

Let it sit in the sun and dry for a few hours or a day.

You'll be left with a very clean and shiny tank.

Now; if you have rust holes and/or heavy rusted 'shale' in the tank, you can seal the tank permanently with "RedKote" fuel tank reliner. This is an aviation quality "liquid vinyl" type compound that you pour in, slowly slosh around to coat the entire tank inside and then pour off the excess. This stuff dries in 24hrs and is absolutely bullet proof after that. If you have holes, tape over them on the outside so the RedKote has something to park against while it cures. Then peel off the tape in 24hours and paint the outside of the tank! If you had rust, sand, crud, 'shale', etc. in the tank, it will be permanently sealed in place....forever.

The only drawback to Redkote is that you must be careful not to seal off vent pipes, fuel pickup pipes or screens, internal baffles, etc. Once this stuff dries, that's it, your screwed. So, go out of your way to keep important things open and clear.

I've done 4 or 5 tanks like this with fantastic and permanent results.

Now in your case where you just have some funky fuel living in there, you may not need to be so agressive. You may be able to just pull the tank, pour out the bad fuel, slosh some carb cleaner around, pour off, dry with compressed air and be done.

[JMela]

The POR-15 people have a 'fuel tank repair kit' for $55.

[230/8]

Before you get to rough with your tank, you might want to just check on how the interior is coated. I believe MB tanks have the interiors coated with a corrsion inhibitor. I also believe some newer cars have a soft epoxy-style coating that helps to resist leakage in an accident. Helps with rust too. If you get too aggressive with your cleaning you may end up loosening up stuff that will plug your system. Also, most tanks have a system of vents and baffles. These need to be kept open. There is a sump for the pick-up and also the fuel level sender fits into the free space. A lot is going on inside that tank.

Maybe a call to Mercedes Classic Center can answer a few questions?

If you have stale gas in there then just drain the tank, add a few gallons of fresh fuel, rinse it around and drain again. If the tank is not leaking it should be fine.

For what it's worth...

230/8

[UPSTATE NY]

Hello, thanks for the input. I spoke to to a friend who suggested 2 gallons of carburetor cleaner into the tank for -2- weeks. It's been 10 days, I looked into the tank thru the sending unit fitting and the old gas is breaking up.

I'm going to rinse out the tank several times with -5- gallons of gas and see what I come out with, so far, it's cheaper than a new tank.

Thank You

Later
JOB