Fuel tank leak?

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19_Hue_95

19_Hue_95

Active Member
Posts
100
Location
Midlands
cybQFp

Recently (yesterday) bought her. She drips a bit of oil from here and there but most do.

But I got her home after a hour or so drive today and parked up, it's rained all day, I noticed a trail of 'oil slick' (the rainbow pattern - not sure on the correct name) on the path I drove her in on. Looked underneath and could not see any drips appear from odd bits of water off the mud flaps. Moved her forwards and there was a huge oil pattern on the floor - granted oil dispersed in water, but this was a huge mess. The culprit seems to be a really oily / fuel covered part of the rear. The photos are very bad, I could not get a good shot with my phone, but it seems to be on the fuel tank and to the parts of the chassie to the left (exhaust side) of it. I can't see any components above it which would leak this so I am thinking fuel tank.

But then again, if it is the fuel tank why is it all the way across on the rest of the rear end?

It's not leaking as such, I can see no drips, oil level is perfect and has not moved. What I think is happening is the splash from road water is dripping off and washing off some of the oil with it.

For reference it's a 300tdi long wheel base station wagon.
 
19_Hue_95 said:
cybQFp

Recently (yesterday) bought her. She drips a bit of oil from here and there but most do.

But I got her home after a hour or so drive today and parked up, it's rained all day, I noticed a trail of 'oil slick' (the rainbow pattern - not sure on the correct name) on the path I drove her in on. Looked underneath and could not see any drips appear from odd bits of water off the mud flaps. Moved her forwards and there was a huge oil pattern on the floor - granted oil dispersed in water, but this was a huge mess. The culprit seems to be a really oily / fuel covered part of the rear. The photos are very bad, I could not get a good shot with my phone, but it seems to be on the fuel tank and to the parts of the chassie to the left (exhaust side) of it. I can't see any components above it which would leak this so I am thinking fuel tank.

But then again, if it is the fuel tank why is it all the way across on the rest of the rear end?

It's not leaking as such, I can see no drips, oil level is perfect and has not moved. What I think is happening is the splash from road water is dripping off and washing off some of the oil with it.

For reference it's a 300tdi long wheel base station wagon.
Click to expand...

Sometimes the tanks leak from the sender gasket in the top of the tank, sometimes they leak from a rusted seam, the tanks are made in 2 pieces, and welded together.

A small leak will run over the tank, and it may not be obvious as a single pool underneath. And the air turbulence round the back of the vehicle will spread fuel all over the place while you are going along.
 
In fact scrap that. Just went and had another look it's physically ****ing fuel out. Money down the drain - literally.
 
19_Hue_95 said:
In fact scrap that. Just went and had another look it's physically ****ing fuel out. Money down the drain - literally.
Click to expand...

From where though - as @Turboman says from the sender gasket half way up the off side of the tank or has your tank rusted through. One of the issues could be the return pipe that fits to the top of the tank (difficult to diagnose) The tank guard (if fitted) doesn't help either as is captures the lost diesels and it gets blown everywhere when driving.
 
doriz said:
From where though - as @Turboman says from the sender gasket half way up the off side of the tank or has your tank rusted through. One of the issues could be the return pipe that fits to the top of the tank (difficult to diagnose) The tank guard (if fitted) doesn't help either as is captures the lost diesels and it gets blown everywhere when driving.
Click to expand...

I can't really tell. The offside (exhaust side) is covered in congealed fuel, but does not appear to be dripping. The actual drip is from the front right hand side of the tank, but with the fuel tank guard on it could be from anywhere underneath.

Come to think about it, I filled her up yesterday and herd a 'clunk' sound after a while, sounded like metal expanding - if the tank is rusty I guess that could of been the sound of the tank splitting under the weight.

My other half decided to call the AA out as 'they will get it sorted for us' - I don't know why she thinks any garage will be open at 7pm on a Sunday!
 
Scooby22 said:
Is it leaking when stood with engine stopped or only when engine running. Does it stop if you point it nose up hill. etc.
Click to expand...

Engine stopped it's leaking, but the trail of fuel was seen when I drove in so guess it's both - again would point to a rusty tank, it's pretty much full at the moment so tempted to drain it off. It's flat at the moment, not many hills to point it on.
 
I think I would take half the fuel out if you have containers for it and see if it still leaks then. As mentioned could be the sender unit seal.
 
Scooby22 said:
I think I would take half the fuel out if you have containers for it and see if it still leaks then. As mentioned could be the sender unit seal.
Click to expand...

Am I right in thinking the sender unit is lower than the top of the tank? So when we got her with 1/2 tank of fuel we would not of seen a leak, now it's full the fuel will be leaking from the seal?
Thought I might of managed to get her home before we had a problem!!
 
19_Hue_95 said:
Am I right in thinking the sender unit is lower than the top of the tank? So when we got her with 1/2 tank of fuel we would not of seen a leak, now it's full the fuel will be leaking from the seal?
Thought I might of managed to get her home before we had a problem!!
Click to expand...

Spot on, it has to be the most stupid design ever. The problem could've been there for years if you never put much fuel in before.
 
doriz said:
The leak will gravitate towards the hole in the tank guard, the same place your drain should be - top tip from @Scooby22 but be aware you are going to need a good sized container to drain off 35+ litres.
Click to expand...

I think 100% it's the sender valve now. it's all heading towards the drain hole. Anybody got any Jerry cans... I don't think buckets of fuel is a good idea.
 
If the tank is weeping from the sender you will be able to see it. nearside wheel arch above the exhaust and between where the rear chassis meets the tub. It has an outlet for the fuel pick up and three wires. If it's leaking with the help of a torch you should see it.
 
Thanks for all the help guys!

Just been crawling around underneath and came to the conclusion it's 100% the sender valve, it's leaking, fuel is running along the fuel tank weld and dripping onto the floor at the front of the tank (near drain screw / valve).

I jacked it up on the curb and it slowed the leak enough so I could work out the problem, but it's not really high enough to actually stop the leak.

The other half called the AA out and I explained the problem (turns out I know more than him....) he plastered it in Chemical Metal adhesive but it took no effect as it's so wet it can't bond.

It's got a big bucket under it at the moment as sadly I don't have any hose or a Jerry can big enough. I'll be buying one ASAP for when something daft like this happens again.

It was heading to the garage tomorrow for an overall service / check up to make a list of things for me to do, so I think I will ask him to get this sorted tomorrow for me as I can hardly afford to let this go on too long!!

Once again, thank you very much all - great community!
 
Might help before you decide to drop the tank which is a PIA.[/QUOTE]
19_Hue_95 said:
Thanks for all the help guys!

Just been crawling around underneath and came to the conclusion it's 100% the sender valve, it's leaking, fuel is running along the fuel tank weld and dripping onto the floor at the front of the tank (near drain screw / valve).

I jacked it up on the curb and it slowed the leak enough so I could work out the problem, but it's not really high enough to actually stop the leak.

The other half called the AA out and I explained the problem (turns out I know more than him....) he plastered it in Chemical Metal adhesive but it took no effect as it's so wet it can't bond.

It's got a big bucket under it at the moment as sadly I don't have any hose or a Jerry can big enough. I'll be buying one ASAP for when something daft like this happens again.

It was heading to the garage tomorrow for an overall service / check up to make a list of things for me to do, so I think I will ask him to get this sorted tomorrow for me as I can hardly afford to let this go on too long!!

Once again, thank you very much all - great community!
Click to expand...

Just remember you have bought and vehicle and joined a community that just never fail to surprise you or fail to keep on giving :D
 
As has already been mentioned, check the fuel filler breather pipe, as it can leak from there on anything more than half a tank, and then runs everywhere.
Cosat of repair/replacement, maybe a couple of quid, and that seems a bit cheaper than a new tank
 
If you knew someone else with a diesel you could have drained it in stages (5 litres) and emptied the fuel in to their tank. and once you fixed yours get them to pay for the same amount back in your tank.
 
Just an update - went into the garage and got the leak sorted, they replaced the vale at the same time, I don't think it needed doing - but at least its done now!

She has since been sat on the road for the last few days, went to clean the engine the other day and noticed it was leaking again. Slightly worried as it might be something else, but close inspection and you can actually see the fuel collecting in the rim at the base of the valve.... back to the garage again.... The mechanic turned around and said "I thought this might happen, previously it was covered in silicon sealant and I didn't put any back" - I gave him the keys and left sharply before I said something!

On a separate note, there is a slight oil leak from the front. I mean really slight - It sat for 2/3 days and there was less than 20p worth 'splodge' on the floor. I have not looked properly but there is one of two things:

a) the engine is covered (and I mean covered) in oil, so there is in fact an oil leak (it was mentioned on the MOT as an advisory). I am cleaning the engine bay up at the moment to see if I can see where it is coming from. The odd thing is that there is no oil below the engine where this possible leak is and where the leak is coming from there is no obvious pathway which makes me think that its either just an amalgamation of 20+ years of crud or when the oil was changed last they got a bit carried away. Either way, once the crud is cleaned off we will see (might make the problem worse if the crud is blocking the leak!!)

b) It is dripping from the gear box drain hole, where the wading bung goes (I think this is more likely). So my question is, if it is in fact this - I can work it out with a stick on the oil leak held vertically to see where it is coming from, is it possible to stop it? I understand the purpose behind it so don't really want to block it, but at the same time I am conscious of parking it on nice driveways / clients driveways and leaving a nice mess!!!
 
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