After scraping the paint and coatings off the bottom of the tank the other day I took a further closer look last night. There is a definite leak. Not much but a weep around the offside lower seal all the same, so the tank has to come out.
The tank was drained down and I cracked all the screws this morning then dropped the tank (screws had only been on three years so no issues with them). I also realised this was the 'Bomag tank'. A std rear fill that I had modded to a military'ish spec to do the job. Not that that is an issue.
Firstly pressure washed after a spray of kerosene and then a stiff scrub with a brush. As per the base of the tank the paint peeled off some areas very easily. Poor prep on my part?
The inside looked in mint condition bar the grime residue from the WVO/dieso. To degrease and clean out the interior I added two bucket loads of hot water with bio washing detergent to cut through the grime then forced my hand through the filler and gave it another scrub followed by a rinse out with the pressure washer. Then repeat the whole thing again with more hot water/bio/rinse.
Looking at the internals after it had dried out there was nothing obvious that's causing the leak but the coating does look thin especially on the rear wall. This is a common point of breakthrough anyway. The fuel also seems to be coming from behind the lower section of the support plate at the rear so it is probably leaking from a pinhole, passing between the plates then leaking at the lowest point?
After the addition of the hot water etc. the paint coating came off easily and in the end around 50% of the old stuff came off. These areas were clean then sanded back with coarse paper to bare metal ready for some quality zinc primer. Two coats of Smith & Allens 'galvafroid' equivalent later it looked like this. Exterior grade black gloss to follow plus black waxoyl underbody seal on the four vertical sides before install.
The original interior coating was POR15 Tank Seal and last time I used a 950 ml can shared between both tanks. I will stay with the same stuff but I don't really need half a liter...but I will get it anyway as 250 ml is only £7 less! Still £25 a pop!? This will be here next week.
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As Trig's was temporarily down one tank I needed to get him running for the weekend. As the RH tank had already been drained of fuel (around 80% dieso) this was stuck in the LH tank after draining most of that down. I don't want to start the engine cold on high concentration of WVO (even if the weather here is 27-30 Deg.C at the moment).
I took Trig's for a quick dump run and he ran fine. This was the tank that seemed to be suffering fuel starvation on high WVO levels. So it must be a viscosity problem restricting the flow when this tank is used for high concentrations of WVO?
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