Hot fuel filter?

Hi folks, the missus was towed home yesterday by the AA. The fault - a leaking fuel filter and stripped water trap - again

This is the second filter and water trap in as many months.
The garage has pointed to faulty parts and I know plastic threads are not the best in the world but surely you know when one has stripped i.e at time of fitting.

I have done a search and it seems that this is not unheard of on TD5 Discos but I am puzzled as to how it can happen post fitting?

I checked the new filter for leaks today and it is dry but was hot to the touch even after just starting from cold - is this normal or is the heat contributing to the failure of the threads?

Thanks,Will.

are they over tightening

williamraff said:

Hi folks, the missus was towed home yesterday by the AA. The fault - a leaking fuel filter and stripped water trap - again

................. - is this normal or is the heat contributing to the failure of the threads?

Thanks,Will.

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Hot filter on a TD5 is normal. Re the threads, someone is over-tightening.

Thanks - hopefully they have learned not to swing on the spanner and this one will be ok?

Hot is definitely possible. Fuel flow is from tank to filter at "low" pressure, back to pump in tank, then at 400 bar up to injectors - that's enough to get it quite warm! Fuel which is not used is then returned to the tank via a fuel cooler (I think that is the right order) which uses engine coolant (i.e. close to 100C). It goes via the fule filter on the way back if I remeber correctly.

Cheers!

Cheers Graham, makes sense actually when I think about it, Will.

Graham Carter said:

Hot is definitely possible. Fuel flow is from tank to filter at "low" pressure, back to pump in tank, then at 400 bar up to injectors - that's enough to get it quite warm! Fuel which is not used is then returned to the tank via a fuel cooler (I think that is the right order) which uses engine coolant (i.e. close to 100C). It goes via the fule filter on the way back if I remeber correctly.

Cheers!

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NO!

The Fuel leaves the high pressure stage of the fuel pump at FOUR bar (say 60psi) held to 4 bar by the fuel pressure regulator on the rear right of the cylinder head which controls the fuel pressure OUT of the head. Fuel at 4 bar fills the injector gallery. The Injectors are struck by a CAM LOBE and that makes pressures in the injectors of about 1,500 BAR (one thousand five hundred BAR, well over 22,000 psi. THAT is what makes the TD5 fuel so hot when excess fuel is spilled from the injectors back to the gallery, then out of the head, through the fuel cooler, and back to the tank.

Thanks for the clarification Charles - in that case there would be something wrong if the fuel filter did not get hot?
Will.

williamraff said:

Thanks for the clarification Charles - in that case there would be something wrong if the fuel filter did not get hot?
Will.

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yes, and sorry for the delay.

The fuel is VERY hot when it leave the cylinder head, and is cooled to about 70°C in the fuel cooler.

The filter will usually be too hot to hold with bare hands after a few miles.

CharlesY

The usual cause of a TD5 fuel filter leaking is TOO MANY SMALL CENTRAL O-RINGS stuck on the underside of the filter head.

This is easy to happen - you take the old filter off, and the BIG O-ring comes off, but the little one stays stuck on the filter head, out of sight.

You put TWO new o-rings on the new filter, and screw it on. Now you have one large o-ring and two small ones. This alone may stop the filter from sealing on the large o-ring.

Next time you change the filter it may do the same again - leave the TWO small o-rings behind, and then you fit another new filter with both new o-rings, now making THREE small o-rings in place, which will almost certainly mean it is going to leak around the edges of the main larger o-ring.

Thank god I'm not the only one who didn't check the small o ring being left on causing a leak & worrying about a hot fuel filter. As I can now consider myself normal can someone tell me why that on occasions l put my foot down to go & it doesn't. New filter & fuel pump fitted, new maf & map.

muddymac said:

Thank god I'm not the only one who didn't check the small o ring being left on causing a leak & worrying about a hot fuel filter. As I can now consider myself normal can someone tell me why that on occasions l put my foot down to go & it doesn't. New filter & fuel pump fitted, new maf & map.

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Could be the fuel your using? I used a local Tesco garage and it was well down on power after about 2 miles of filling it up. Never went back there again

I never fill her right up ( no obvious jokes please ), but l do put in red x additive every time l put fuel in. Think I'll leave the red x out for a while & see what happens. Thanks for replying. Never considered that fuel octane rating for a diesel would be a problem.

muddymac said:

I never fill her right up ( no obvious jokes please ), but l do put in red x additive every time l put fuel in. Think I'll leave the red x out for a while & see what happens. Thanks for replying. Never considered that fuel octane rating for a diesel would be a problem.

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Not the octane rating, just crap in there tanks I believe

The mechanic next door had a disco 3 in saying it was down on power, they changed the filters and was still the same, I asked him to ring the owner and ask where they filled up last! Yes it was the same petrol garage!

I now don't think it's the fuel. Started her up, all OK, put my foot down to go, ziltch. Ticking over OK, pumped the gas pedal, nowt. Cloud of white smoke, then all OK & drove home quite happily & didn't miss a beat. No loss of water or oil. Just tried her again, perfect.