Advice before i drop fuel tank - fuel leak

Hi All

Been a busy beaver since i bought this MK1 GTI cab, nothing majorly wrong but in typical form - as soon as one thing is fixed or replaced something else pops up!

After changing water pump, some hose clamps, heater matrix, oil cooler, timing belt and tensioner i decided to take it for a good Squirt down the back roads and on the way back for the first time since buying i filled it up to the brim with fuel.

Since owning its had a slight smell of fresh petrol but never saw any sign of a leak on the floor or on the base of the fuel tank so put it down to me not being used to "old car smell" - anyway went out this morning and my driveway stinks of a filling station, and two damp patches finally revealing my suspicion it have a problem.

slow and steady drips coming down from two areas, one mid tank and one over by the exhaust heat shield - of the two the heat shield side was by far the "wettest" area - although i am not sure if maybe the leak is somewhere else and its just running down to this area?

had it up on stands just now, - and as soon as its lifted the drips all stop.

from inspection - all drivers side is looking fine - pumps and filler neck dry, clamps fine and just one drip to be found at the bottom of a clear braided hose that looks to go up and over the tank to the mid section.
lifted back seats - dry as a bone under the tank access panel.

in the cars history it had work done at a garage under a year ago with the previous owner replacing fuel pump and full new fuel lines - and that all looks fine, like i say no leaks etc - its just coming from the exhaust side.

before i drop the axle to take the tank out to inspect - what would you recommend checking? i had a scour of the forum and checked what i saw there - but short of it being a hole in the tank i cant see why it would be leaking on the passenger exhaust side as from the diogram's i can find i cant see any hoses or fittings there?

any and all advice welcomed

A fuel pump sender seal fail will cause those issues as well as loose or improper clamps on the fuel sender.

I would pull the back seat and the inspection cover to validate that I don't have a leak at the hose connections.

Using the Screw type of clamps is a no-no on fuel lines and the fuel clamps are a must.

There aren't any clamps or hoses on the left near the exhaust, and tanks do go bad, pulling the inspection cover and the fuel sender out will allow you to look in the tank a wee bit to see if it is rusty.

Have you put a spanner/screw driver on the clamps to check they are tight?

As Briano1234 fuel hose clamps must be used and not normal jubilee clamps as they squash the hose in 1 area unlike fuel hose clamps.

Pack of 5 Stainless Steel Mini Fuel Line Hose Clip Jubilee Petrol Pipe Clamps Silver (10-12mm) : Amazon.co.uk: DIY & Tools

Worth removing the fuel sender as it's easy to not get the seal seated right and fuel will leak out when full.

Your tank looks new so should not have any holes in it unless it's a manufactures fault?

As you say theres nothing over the left side of the tank that should cause an issue.

apart from a seam hopefully not

That is correct, however if you have a loose fuel clamp then it can leak at the sender, and when you sit in the car, the weight can cause it to leak on the sender and then go over to the sides of the tank and drip off the seams from the top.

Typical Digifant system:


Typical CIS


Old school Diesels, and Early Gassers were bottom feeders out of the right front corner of the tank. (driver side in the UK and passenger side in USA)

Typically the only place save for a SEAM on the side of the tank on the left is possibly from the Sending unit at the top, and or the fuel filter on the DIGI as it is center mounted.

With the age of these cars and the advent of e-rated fuels all hoses are suspect.



VW used fuel clamps OEM that were the banded and crimped over.




 Folks cut those off and use the Screw Clamps that on smaller diameter hoses can oblong one side and not seal properly and returning fuel can weep or spray about.



Proper screw type of fuel clamp, notice that it forces the clamp to remain circular on the hose and clamp equally around the pipe.

Found It!

bloody hole in the tank - at least 2 that i could see! 

Good you found the problem, will you repair or get new tank? How difficult was it too drop tank, any tips? Thanks Carl

A good Radiator Shop can repair those holes, looks like a puncture from something.  If it was on the top of the tank then look at your frame or under carriage to make certain that what ever it was isn't still able to scratch it after the repair.

Yes wierd unless the filler pipe had gone and filled the tank with cr P and water rotting out from the inside.

Whats the inside look like peering through the sender/pump hole? Clean and shiney or rusty?

Beware I replaced the GTI with a pattern tank and had mega problems with fuel starvation. In the end found a good 2nd hand original thats still working fine.

Hey all

It's relatively easy to take out, but it is a bloody awkward shape - disconnect hoses and remove sender unit, rear wheels off, drop axle off its bolts and lower down on jack - but leave coil overs attached to pivot and it slipped out without too much hassle.

After a closer look today, there are about 7 holes ranging from the one in the photo above to hardly visible pinholes, some of them along the weld seams.

The shame is the tank is in 98% good condition, took a look with a endoscope  - inside it almost looks new apart from where these holes are, then there is a small tiny patch of rust that's eaten through - in the cars history it was laid up in a garage in Anglesey for a few years so I suspect it happened then and all the other owners have just put up with it!

If it was one, then I might repair but as it's a lot , with some in the seams I just ordered a new tank, as otherwise I could see it turning into a reoccurring nightmare.

hi mate where you located

nicci21paul said

hi mate where you located

Hey, North Wales - Just over the border outside Chester

07739608140 give me a ring or forward your number mate

New tank came today - it's certainly a lot easier to take them out than it is to put them back in on a driveway !

Definatly a 2 person job to put it back in - I did it on my own today and it took 4 axel stands and 3 jack's to hold lift and move everything into position.

On a positive note managed to get a overly generous blast of waxoil over everything while it was up!

good stuff, where did you get the tank from, looks good quality?

Carl Jones said

good stuff, where did you get the tank from, looks good quality?

Exceptional quality, comes zinc coated and sprayed silver then I put three coats of black underseal on it before I installed - the black tar type paint,then also gave it a good coat of wax oil (hopefully it will help stave off any rust but made it bloody slippery to handle!)

Got it from heritage parts;
https://www.vwheritage.com/155201075-fuel-tank-55-litre-vw-spare

I think I could have repaired my old tank by welding or could have bought a 2nd hand but wanted the peice of mind of a new one.

The tank looked perfect but it must have been ever so slightly larger as it had to be pressed back into place with a jack and a strip of wood to spread the load - didn't take much force and the wax oil helped it slide in a bit better (that's what she said)
All the holes lined up perfectly so that's great.




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