Cleaning A Gas Tank

[Scottie-GNZ]

OK folks, I know there are a lot of previous discussions on this topic, but I feel this one is a little different.

 

Here is some background. I ran the GNZ the other night and discovered it is running extremely rich, possibly caused by a bad MAF. However, instead of the typical black soot out the exhaust, the back of the car was covered in a light brown soot. I pulled the O2 sensor and it was coated with the same color, telling me whatever it was, was being burned in the engine. I drained the gas and it looked good, so I dropped the gas tank. The bottom of the tank was covered with a black layer that looked like undercoating and I figured that was just sediment that settled over the years. The rest of the tank is coated with varnish. What was not coated had a light green finish, same as the outside if you peel away the undercoating. I assume that is some sort of sealer. I noticed there was a small amount of what looked like small rust-colored pebble (like fine sand) in the tank, and when I pulled the fuel filter, it was loaded with that stuff. Whatever it is turned to a paste when I rubbed it between my fingers. I am thinking it is varnish and what has been getting into the engine.

 

I washed out the tank with soap and water and the sediment on the bottom is all all gone and the tank is in perfect condtion, except for the varnish. The tank has no rust at all. So, what I am looking for is a way that I can clean out that varnish without destroying the factory coating. I do not want to use anything that will take it down to bare metal, which is going to introduce more issues. I do not want to use any of those gas tank refurb kits that assumes the tank has rust. This tank has NO RUST and all I want to do is remove the varnish.

 

Lacquer thinner would do the job but will probably also remove the factory coating and I am leery of things like muriatic acid, so I am looking for suggestions.

 

TIA,

[cygnusx1]

 Scottie,

 

I just did a 240Z tank that had no rust inside.  I started with a clean, rust free tank but I wanted to coat it to fill any pinholes or hidden problem areas in the pinch seam.  I used the KBS coating kit.  The tank came out great.  Even though it was clean to begin with, like yours, I used the full procedure.  The process involves a 1-soap solution, 2-a zinc prep solution, and 3-the coating itself.  Call KBS and ask.  You may be able to skip steps 1 and/or 2 if your tank is good inside. 

 

 

Edited May 26, 2010 by cygnusx1

[Scottie-GNZ]

 Scottie,

 

I just did a 240Z tank that had no rust inside.  I started with a clean, rust free tank but I wanted to coat it to fill any pinholes or hidden problem areas in the pinch seam.  I used the KBS coating kit.  The tank came out great.  Even though it was clean to begin with, like yours, I used the full procedure.  The process involves a 1-soap solution, 2-a zinc prep solution, and 3-the coating itself.  Call KBS and ask.  You may be able to skip steps 1 and/or 2 if your tank is good inside. 

Thanks for the recommendation and I heard about KBS products before and how well they work. However, I don't think I need to coat and reseal mine. I was truly amazed to see how nice the inside of this tank is and it has no signs of any leakage. Maybe I am being to obsessed with getting that varnish out

[hoov100]

I don't know about you guys in Florida, but in california, most radiator shops will boil out metal fuel tanks. I have never done it without re-sealing the tank in por-15 though, so I don't know if it leaves the factory coating or not.

[Zmanco]

I'm pretty sure that since the factory coating is unaffected by gasoline that it won't be harmed by lacquer thinner either. Unfortunately I am only "pretty sure".

[Scottie-GNZ]

I don't know about you guys in Florida, but in california, most radiator shops will boil out metal fuel tanks.

The opposite in FL. After calling 6 radiator shops, I gave up on that. All said new EPA regs does not allow them to work with fuel tanks.

 

Someone recommended and I tried a product called "Super Clean". Used to be made by Castrol but they sold the rights. Bought 2 gals at Walmart (big purple bottle), poured it in, shook the tank around and immediately drained it. 90% of the varnish was gone except for some stubborn spots on the floor. Poured it back and let it sit for 30 mins and now the tank is clean as a whistle. It had soapy foam when I stuck the hose in the tank so it took a long time to get all out, but well worth it.

 

This is now my new degreaser.

[jc052685]

Been using Super Clean for years. Great stuff!!

[JSM]

Hey Scottie, I know you solved your tank issue, but I found a radiator shop today who does do tank cleaning. I'm not about to spend $350 on a tank for $750 car but they do perform the service. Maybe a simple boil down is cheaper. Anyway, if you want the number let me know.

[Scottie-GNZ]

Thanks, and I feel the same as you about spending that kind of $$$. The Super Clean method should clean anything short of a rusty tank.

[cockerstar]

Another option would have been POR-15's Marine Clean.

 

2 quarts of it came with my gas tank coating kit, so I'll let you know how it turns out!

The whole thing cost less than $80 locally, so it wasn't a huge investment. $350 to clean and coat a stock tank is ridiculous! I thought the $160 the rad shop here quoted was too much. Maybe I'm just too cheap.

[letitsnow]

Marine clean works good, I also like simple green. Simple green won't touch most decent coatings unless it's near boiling.

[JSM]

I just went through Phase I of my cleaning. It is a tremendous amount of work. I'm shocked the car even ran. The amount of rust was staggering.

 

I found a method of filling 1/2 the tank with water, add a gallon of muratic acid and then the rest with water. It did a great job, but I need to do it again. It still has a bunch of rust left. I flushed and flushed and flushed, shook and shook and shook. I was sore the next day. I used golf balls to brake up the rust. I would not do it again. I finally had to use a vacuum to get them out. (I know, I know no vaccums).

 

I bought a 9.99 hair dryer from walgreens and tapped it to the tank. I ran the sucker for at least an hour and it didn't blow up! (Hair dryer, not the tank.) I've got the tank in the house now in the cool a/c. Wife is not all that happy about it.

[bobbyc]

use gloves with super clean...it'll eat the skin off your hands!

[cockerstar]

Used the Marine Clean on the tank today and it looks fantastic!

The inside of the tank literally looks brand new with zero rust. I think I'm still going to go through with the coating though. It'll only make things go more smoothly in the future.