Petrol tank renovation

[stubmw]

Hi, has anyone had success sealing a bmw tank that has pinholes?
Do any of the proprietary sealers work considering the bmw tanks have that red liner? The internals are not severely rusted on mine, but it is a bit scabby. The only bad rust is around the petcock and this is where the pinholes are. Obviously with the lip at the filler its not easy to get bits out (screws, gravel  etc.)
Stu

[montmil]

Stu, Do a search of the archives. There have been many threads regarding tank sealers. Avoid asking the search to do 'all times' or whatever as it may not work too well. Try 'previous year' and go from there.

[stubmw]

Thanks for the tip montmil, i kept getting 'error '  from my search input.

[raphski]

I was having difficulty searching as well and discovered that for me the search bar with the magnifying glass icon didn't work well but my searches using the search button close to the top center of the screen did. If you are using the upper right try the other search bar.
Raphael

[Terry]

Cleaning the tank first with vinegar worked well for me. I let it sit for one week full to the brim with vinegar I bought at the supermarket for $1.60 a 2 litre bottle. Any pinholes will appear as small rusty weep marks. The vinegar is the first step.. If you are getting red paint flakes then you will need to use a stronger remover.. I had a tank that was rusted and it also had been very poorly relined with a sealant.. I removed the lining with a plumbing product. I bought the plumbers priming fluid at the hardware store as it was clear and not pink coloured and contains MEK. Diligent flushing with this  fluid over about 6 applications got the majority of the loose lining out.. I inspected the inside with a small led torch on a string to check for remnants.. I used a chain inside the tank and shook it around many times to loosen flakes and rust particles.i also used a grabbing tool to pick bits off that were stubborn. After I was satisfied that no more would come out I used rust converter (phosphoric acid) bought at the same hardware store to convert any remaining rust to a very clean and bright finish.  Be careful as the pin holes leak .. I taped them over with duct tape when rust converting the inside. I thoroughly washed the inside with hot soapy water after each application and inspection and used mentholated spirits to absorb any moisture as well as drying the inside with a hot air gun..I repaired each pin hole( some as big as a match head and others twice as big ) with Devcon.  This repair takes the most time as the Devcon takes ages to harden and not run inside the hole or down onto other good  parts of the tank. Do one hole at a time as you will need to spend at least an hour on each repair waiting for it to harden to the point it won't run. The trick I learned was to mix to Devcon and wait until it started to set to a blue tack consistency, before application. I also ensured that some Devcon actually ran inside the holes and with careful rolling and turning you can cover an area inside that is two or three times the size of the pin hole.. This was my safety insurance as the tank will be thin around the hole. Clean around each hole until you have bright steel too before applying the Devcon. After leaving the final repair for a few days to fully set I tested the tank with water. Then I put in the POR SEALER. THIS IS A MISSION AS YOU NEED TO SEAL THE TAP AND THE FUEL CAP.
Plug the tap with a dowel and I used a plastic irrigation bung for the cap hole, also bought at the hardware store.they worked perfectly..
The POR sealer needs careful rotation around the full interior for at least an hour or more.. I inspected the coverage each 15 minutes until I could see that it was starting to congeal to a consistency of honey.  My air temperature was 30 degrees so it took ages. Keep at it until the sealer appears to not want to run freely anymore. Then drain the excess into a tin. Leave it to set for a few days. I wiped some  around the fuel cap throat with a rag for God measure. The inside is like a bought one and it is well worth the effort.. I tried multiple things to fix my tank and found that this gave me the best results without welding. Devcon is neutral and can be sanded and painted. Lots of effort with top class results.

[Terry]

Devcon filled rust holes after rust treatment and lining removal and POR final seal

[stubmw]

Thanks Terry, thats a lot of info.
 I have cleaned up the inside with' spirit of salt' , sold as drain cleaner over here, pretty nasty stuff, definitely need to take care with it, seems to have worked though. Now can't find any phosphoric acid, may have to use the POR 15 etching solution for the next stage. The pinholes in this tank are almost undetectable from tge exterior so don't need a filler.  They are concentrated around the tap and equivalent area on opposite side of tank, the rest looks ok, so fingers crossed.
Stu

[stubmw]

So i cleaned the tank, lots of red bits and rust came out. Then used por15 metal prep followed by  por15 tank sealer, followed instructions. ...especially made sure all was dry inside before sloshing sealer around for an hour or so. Left it a week and put petrol in, immediate leaking from pin holes.......?
 Been having fun out on the road with my other tank installed though

[Bob_W]

When all else failed, I went to a radiator shop. The tank had been previously lined with an unknown product, but it was coming loose. Treatment took a couple of weeks and removed the paint, but I then had a clean tank-inside and out. The shop pressure tested and soldered the pinholes. I used a phosphoric acid etchant bought at a local builders supply store. I put rattle can paint on the exterior to stop the surface rust. Someday, I will worry about making the old airhead look better, but in the meantime, it is like the owner-not near as old as it looks.

Bob

[montmil]

 Well done.

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