Thread: Slow fuel leak from tank area

TD5 ???

Could be worth dismantling your fuel cap and cleaning the vents out
I had fuel seeping out around where the fuel lines go into the tank and fuel would spread all around the tank must've been pressurising the tank, cleaned and blew out the vents in the cap all good now

It's a 300 tdi.

mrb505, that sounds similar to what I'm experiencing. When I fill up on diesel, when the tank is getting full diesel starts bubbling out from the outside the pipe at the opening.

Is it fairly straight forward to take apart the vent? Does the tank need to come off?

I meant the vent in the fuel cap itself.
You can dismantle the fuel cap and there is 2 one way valves inside 1 to let air in and 1 to let air out
The valves are just a small spring and ball. On my TDI cap there is 2 screws that hold the first metal plate with lugs to hold the cap on then you can prise the sealing ring off and there is another 2 screws that hold the vent assembly to the plastic part of the cap anyway I just gave the vent assembly a good wash and blow out and made sure the balls moved in and out freely and haven't had any fuel leaking out since
The pipe that comes from the tank to the filler assembly should be at the 12 o'clock position the filler assembly can be turned around, well at least on my tray back , when I first got my defender the pipe came in at the 6 o'clock position and it was a bugger to fill.

Hi tas,

I had a similar problem, when I lived in a damp place , I thought it was a common failure in TDis
The tank has an integral bash plate and the sealant breaks down around the edges and water gets in between the tank and bashplate and the tank bottom gets pitting corrosion holes.

The tank has to be removed to fix this problem. When i did mine tdi tanks were not easy to come by second hand and I could have been just buying another problem.

When the tank is removed you can remove the bash plate by drilling out the spot welds. I scrubbed the bottom of the tank, rinsed it out, put an air hose inside with low flow, to prevent fume build up, and soldered up the tank with plumbers solder ( bakers soldering flux is good ). afterwards i leak tested with water, painted with cold gal, and underbody sealer.
While I had the bash plate off I slotted it all over with an angle grinder to make it easy to clean between the tank and the bash plate with the hose

Then put blobs of neutral cure silicon in a pattern on the tank to maintain separation between the tank and the bash plate, pop rivet the bash plate back into position. That was 12 or 13 years ago, the fuel tank is still going strong.

cheers simmo