So after removing the internally rusted gas tank from my 72 VC, I found another used tank for cheap and thought it was my lucky day. That is, until I realized they don't make new sending units for this tank. The old sending unit looked like it was dredged up from a shipwreck.

I took another look at it this morning, and just slight fingernail pressure started to remove the caked on rust from the tank, exposing relatively clean metal underneath, so I'm hopeful that I can reuse the sending unit even if it doesn't read properly (I tested it and nada).

That said, how should I go about cleaning it? Soak it in thinner? Wood alcohol? Should I use a metal etcher or a rust remover on it?

As for the sock, it completely disintegrated when I touched it. Anyone know what part # I need for the sock, since the sending units are not available anymore?

Thanks,

JP

 

I have had good luck with soaking in 1/2 white vinegar 1/2 water, Don't get in a hurry let it soak for a few days, Has worked for me, Good luck,
As far as the sock goes you can use without that, Just put a filter BEFORE the fuel pump
Johnny

 

Thanks for the tip! Works perfectly for me, since I'm headed out of town and can let it soak for a couple days.

There's no reason I couldn't put a filter between the tank and the hard line at the back of the wagon, so that's a good workaround. Not much room for a filter in the engine compartment owing to the short space between the hard line and the pump.

 

Socks are available in 2 sizes, one for 5/16 and one for 3/8. Google it and alot of venders sell them.

 

Are you worried about removing rust only on the rheostat, or are you trying to do a cosmetic cleanup of the entire sending unit, including the mounting plate and the tubing?

 

I apologize for the hijack, but since I'm working on the exact same problem today I thought I'd ask about it here.

My sending unit also looks like it was recovered from a Spanish galleon. The sock is completely disintegrated. Although it looks like there's a mounting flare on the tubing where the sock connects, after removing the sock there's nothing there but tubing. The original filter screen had a plastic tubing and a cylindrical plastic screen around it:



I haven't been able to find a replacement part that looks like the original, but I have found replacement parts that have a metal disc at the mounting end and are sewn shut at the other end, like this:


How do the replacement socks mount? Do I need to flare the end of the tubing for them to press on, or do they just slide up the un-flared tubing and get held on by friction?

If this helps -- I found the filter sock on ebay:

http://www.ebay.com/itm/Buick-Pontia...3D400667404676

thanks.

bob

 

More or less trying to remove rust from the entire assembly. The rheostat has some greenish oxidation on it, so I assume it's copper. Heck, it may even work after getting cleaned up. Any tips for specifically cleaning up the rheostat?

 

No problem, I like your reference to a spanish galleon, but I didn't find any gold doubloons inside mine, just iron oxide. :P

I ordered a new sock from Summit Racing. Seems to be a common GM component, and I got the 3/8 size. http://www.summitracing.com/parts/OER-K405

Hopefully I ordered the right part, I'll probably have it today or tomorrow. Meanwhile, the tube is resting in a 5 gallon bucket of vinegar water. I tried a garbage bag first, but I kept puncturing it with the tube. I haven't yet gotten the last bits of the old sock (basically the metal ring) off the tube, because I was hoping the acid solution would help loosen things up. Did you just take some pliers and twist it off? When I get the new sock, I guess I'll see what you mean about fitting it. I'm hoping it isn't quite so generic that I have to flare the tube.

 

The reason I asked about this is becuase I haven't done the cleaning on mine yet. I was considering electrolysis, or vinegar, but I'm not sure if I want to do either one. The problem I'm worried about is damaging the rheostat. Or assuming that I don't damage the rheostat, once all of that oxidation is gone from the tubing, you've got nice clean bare metal that is ready to rust. It's going to require some sort of protective coating on it or it's just going to rust all over again. Maybe even faster now that it's been cleaned and it's going to sit in an alcohol / vinegar solution with today's gas. I know that when they manufacture these things the tubing probably receives an electroplate coating of some sort that we won't be able to provide. I'm thinking that if I clean it up so it looks nice, it'll just rust all over again.

I've given some thought to just cleaning up the rheostat, cleaning the mating surface of the mounting flange, and leaving hte rest of it as-is. either that, or completely replacing the tubing with stainless line and tacking the old rheostat onto the new tubing (if it still works). The only other option is to buy a sending unit for another application and fabricate something similar.


I didn't have to use pliers. The plastic mount was so old and decrepit that it just fell off, leaving unflared tubing behind.

No doubloons in my tank either -- only a couple of rocks.

 

The vinegar solution did a pretty good job on the sending unit over the weekend. The rheostat seems functional, but maybe the positive contact is bad. I get variable resistance measured on the metal strip from the float, but infinite resistance on the associated connector pin. Has anyone taken that contact point apart? I don't want to break it, and I'm not sure how I'd get it to go back together if I took it apart. Seems like maybe it was just punched through the metal plate. Thoughts?

 

Hmm, it seems that the metal strip is a bit loose until I twist it in a particular direction. Then I get variable resistance on the connector. Nice, but how do I get it to seat properly so that it doesn't get loose again... /scratches head

 

I did the vinegar thing for a day, it didn't really seem all that helpful in getting rid of the rust. It looked like the acid was etching the non-rusted metal and wasn't even effecting the rust, so I pulled it out of the vinegar solution.

Now I've got it in an electrolytic bath using sodium carbonate and a battery charger. It's doing a great job of cleaning off the external rust. I'll probably have to disassemble the rheostat housing to clean the insides once the exterior cleaning is done.

It's hard to imagine exactly what your electrical connections look like without a photo. A picture of where you're taking your measurements, and what's loose, would help a lot.

If your electrical connections are loose, can they be soldered?

 

Good thread guys. I was thinking solder too. There are 2 strengths of vinegar as well. I use it in my work, as far as the white goes. 5% is the norm, household stuff that must folks use for the coffee makers and such. 9% or pickling vinegar is much stronger and works
a lot better. Try it with a brillo pad if you have hard water stains on your windows, you'll see what I mean. Good luck guys, you have to do with what you have to work with if especially if there are no longer replacement parts available. Quick thought, I wonder if the guys in Cuba had a thought or even cared about how much fuel they have in the tank. They may know something we didn't think about.

 

Funny how when you take a look through a different lens, you see something you missed the first time around. Since you asked for the pic, I noticed that the wire strip is held in place with a tiny speed washer. Without the magnification, I couldn't tell. So I guess smart money would be to remove the speed washer, solder the strip to the post, and put the speed washer back on.

The outside of the sending unit looks pretty decent, but I'd feel better about running a pipe cleaner or something through it. Spending a short amount of time googling online and on the phone with my local hardware store, I couldn't find anything both small and long enough to do the trick. I'm thinking that I'll run a flexible wire through it, pulling a thicker cloth cord soaked in solvent behind it. I want to at least remove anything that the vinegar loosened.

BTW, that's very slick about creating your own electrolysis bath.

 

I was half tempted to dilute muriatic acid but since I was too lazy to research the acidity that would match vinegar, and didn't want to return from a weekend to find my fuel sending unit disintegrated, I thought the better of it. :P

I've been wondering about those Cuban cars and if any of them will end up in the USA any time soon. My stepmom recently went on a humanitarian trip there and got taxied around in a nice convertible.

 

Be glad you didn't use muriatic,it would have ate it. Put a small dish out and
a small piece of aluminum, wow. Made that mistake years ago with a cast iron carb from an old massey tractor. It actually ate the AL butterfly, oops.

 

 

Well, I don't know how "Cuban" this approach might be, but when my sending unit isn't working I just fill up the tank every time I go somewhere, and refuel after I've driven for a while. Maybe I should get a long dipstick to shove down the filler neck into the tank until I fabricate a new sending unit.

 

^^^ I'm not sure what material the binding post is made of on your sending unit -- yours looks like it's a pin with a speed nut pressed onto it. Mine has a brass stud, a brass washer and a brass nut.

I'm being careful to keep that binding post in the air (dry and out of the solution) while I'm doing my electrolytic cleaning, because electrolytic cleaning takes a while with iron but will rapidly consume anything made of copper. So instead of just dumping my sending unit in a tank and letting it bubble, like you can do with something made of iron or steel, I'm going to have to reposition it periodically to clean different surfaces while not exposing the brass fittings to the liquid.

Just FYI here are a some photos of the electrolytic cleaning process:

This is what the setup looks like while it's cooking. Just a solution of washing soda in water, with a battery charger with the (+) lead connected to a 9 inch spike, and the (-) lead connected to the part being cleaned. Lots of fizzing when you first get started. The clear solution quickly develops rusty scum coming off at the anode (spike). You can see the white bubbles rising from the cathode (along the outline of the part being cleaned).



It takes no time at all for the sacrificial anode to get so encrusted with rust that it slows down progress, causing the output current of the charger to drop off. This is what a polished spike looked like after 20 minutes in the bath:



If you let the reaction run without removing the spike for cleaning/polishing, the rusty crud quickly accumulates on the spike, impeding the progress of the reaction. The result is that the output current of the charger will drop to near zero and not much will happen over time. In other words, the accumulated crud slows down progress so much that people like to say it's "safe" to leave it running overnight. Me, I prefer to clean the electrode frequently to speed up the process. When the iron is clean you get plenty of amps and the cleaning process is fast ... but current drops off quickly as the crud re-accumulates and you have to clean it again. I really need a larger anode, like a steel plate. This spike was the only piece of scrap iron that I had on-hand. I didn't plan ahead.


.

 

That is really cool. Thanks for the pics. I'll have to try that next time I'm cleaning up something rusty. Cheaper than gallons of vinegar, too.

 

Wow, the electrolysis produced some really good results.

Prior to electrolysis, my sending unit was a rusted hunk of junk that wouldn't send any signal. No matter how I positioned the float arm my VOM read infinite resistance.

After 2-3 days in the electrolysis bath, a huge amount of crud came off of the sending unit, leaving behind only a dark black patina where the crust rust had been. Best of all, the sending unit now signals 0-30 ohms when I move the float arm!

Here are some before-after pics for comparision:










Now I get to cut a gasket and re-mount the tank.

 

I believe you can buy a sock, they're pretty standard. As for rust removal, use Evaporust. You can get it at Harbor Freight. Works great and is reusable.

 

regarding cleaning with chemicals versus cleaning with electrons:

i've used vinegar. it can get expensive.

i've used evaporust. it worked nicely. but it took an entire 4 oz sample bottle to clean the rust off of a 3/8" line wrench, and after cleaning the wrench, the solution was spent. it wouldn't clean anything else.

one problem with chemical redox reagents or chelating agents like evaporust is that they are all consumed stoichiometrically by the chemical reaction that cleans the rust; if you've got a little surface rust to clean, then you won't consume much of the solution and it can be reused again and again. if you've got lots of heavy encrustation then you may well consume the more than one bottle. chemicals can get expensive when you have to buy bottle after bottle.

another problem with the chemical reagents is that liquid solutions have volumetric weight, which adds shipping expense to the price of the reagent. for a big job the cost can get pretty high. then you have to go fetch the bottle. for me going to HF also involves an hour of driving.

for a heavy rust job, electrolytic removal works well. it cleans the rust completely, it only costs as much as running a battery charger, and it works using products that you probably have on-hand: scrap iron, battery charger, sodium carbonate, electricity. the only reagent that is consumed in the electrolytic reaction is the electricity, at the cost of running a battery charger. the washing soda isn't consumed by the reaction, so there's no real cost in terms of chemicals.

I posted the info about electrolysis just to let people know that there's another option available besides the chemicals in jugs.

 

Thanks for your input on the electrolysis and comparison to other techniques. I will definitely try this next time. For safety sake, what do I not want to do with physical contact between the sodium carbonate bath and the clamps? I'll just crud up my clamps, or something worse? How much sodium bicarbonate for a 5 gallon bucket?

Final results for my project are that I got the new/used tank installed over the weekend, wired back up, fuel lines put together, poured 3 gallons of gas in, and after a couple minutes of periodic cranking, the motor fired up. The gauge reads more or less correctly. I think the resistance on mine is more between 0 and 80-ish, but I'll see what a full tank looks like as soon as I transfer ownership on the car and register it in my name. The paperwork is still in my mom's name.

We made it a family car wash day, put my wife and 2 kids in the back seat and drove it around the block. Good acceleration, smooth idle and smooth ride. Felt like a king of the road!

I still need to investigate a strange almost mechanical sounding pop that I occasionally heard from just in front of the driver position while both a low speed in close succession on a non-bumpy stretch of road, and also when I stepped on the brakes at 55mph. Not sure if that's something in the steering, the linkage, or the power booster, but I may be opening another thread as I get more road time.

Thanks for everyone's help in getting this monument back on the road.