How to access petrol tank in 740?

cr80442

I'm trying to access the top of the petrol tank through the boot but I can't remove this big black sheet metal thing. Any ideas?

Major Ledfoot

Ooooooo, you have the auxiliary Bränsletank.

https://www.volvopartswebstore.com/products/Fuel-tank/1113792/1389471.html

carnut222

Yep you have to remove the auxiliary tank to access the main tank sender. It's pretty fiddly as you need to lift up the aux tank enough to access the hose clamps connecting the aux tank to the filler hose joining the 2 tanks. I don't envy you with this job as it was a bitch when I had to replace the leaky filler hose on my 740T.

cr80442

carnut222;116188 wroteYep you have to remove the auxiliary tank to access the main tank sender. It's pretty fiddly as you need to lift up the aux tank enough to access the hose clamps connecting the aux tank to the filler hose joining the 2 tanks. I don't envy you with this job as it was a bitch when I had to replace the leaky filler hose on my 740T.

Can I delete the auxiliary tank

carnut222

Yes you can delete it but you will need to replace the main fuel fill hose (the large one in the pic) with the standard hose for a car without the aux tank. You'll also need to block off the square hole in the floor with a metal plate that can also be sourced from a car with no aux tank, or DIY. Some other smaller vent hoses will also have to be modified. If you can find a parts car without the aux tank to look at and scavenge parts, that would help. If you do it, I'd recommend replacing the large fill hose with a brand new one as they do tend to fail with age so a used one may not last too long. If you do it on the cheap instead of buying a new hose you can block off the hole in the existing hose with a metal jar lid that fits the hole and a hose clamp to hold it in place. Not recommended though!

cr80442

carnut222;116191 wroteYes you can delete it but you will need to replace the main fuel fill hose (the large one in the pic) with the standard hose for a car without the aux tank. You'll also need to block off the square hole in the floor with a metal plate that can also be sourced from a car with no aux tank, or DIY. Some other smaller vent hoses will also have to be modified. If you can find a parts car without the aux tank to look at and scavenge parts, that would help. If you do it, I'd recommend replacing the large fill hose with a brand new one as they do tend to fail with age so a used one may not last too long. If you do it on the cheap instead of buying a new hose you can block off the hole in the existing hose with a metal jar lid that fits the hole and a hose clamp to hold it in place. Not recommended though!

When the cars tank is completely full it leaks out underneath so I think it's the auxiliary tank that leaks

carnut222

Exact same happened on my 740T and it was a split in the small hose (#4 in the drawing above) joining the 2 tanks together. I doubt it is the tank itself. Likely to be either the large or small hose.

Vee_Que

That's common. And it's a common hose to replace it but I never had to do it.

cr80442

carnut222;116198 wroteExact same happened on my 740T and it was a split in the small hose (#4 in the drawing above) joining the 2 tanks together. I doubt it is the tank itself. Likely to be either the large or small hose.

Thanks heaps

Ghettobird

This is easy stuff

Get under the car with a light and have a look at the hoses that run from the aux tank in the boot & the main tank.
You may find a hose has popped off, or if the leak is when the engine is running the main fuel line may have perished.

IF you do diagnose the aux tank as the issue, get under the car with a phillips screw driver, a 7mm 1/4 socket or ratcheting spanner & a flathead screwdriver and loosen everything off - There is a main hoas clamp that conjoins the aux tank with the main tank, a breather hose & another hose or two.

The most common lines to fail are the breather elbow and the main pressure fuel hose that goes to one of the sideways barb fittings on the main tank.

There is nothing wrong with the aux tanks, you just need to be smart & not just go trying to rip things out

cr80442

I've had a good look, all the hoses are intact. It only leaks when you fill the tank up all the way and it leaks a few litres then stops.

carnut222

I agree with Julian - must be hoses or clamps...sometimes a small split is hard to spot.